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Old July 16th, 2012 #1
Roy Wagahuski
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Default Animal domestication: Can a fox become man's best friend?

Animal Domestication
Published: March 2011



Taming the Wild

Only a handful of wild animal species have been successfully bred to get along with humans. The reason, scientists say, is found in their genes.

By Evan Ratliff
Photograph by Vincent J. Musi


"Hello! How are you doing?" Lyudmila Trut says, reaching down to unlatch the door of a wire cage labeled "Mavrik." We're standing between two long rows of similar crates on a farm just outside the city of Novosibirsk, in southern Siberia, and the 76-year-old biologist's greeting is addressed not to me but to the cage's furry occupant. Although I don't speak Russian, I recognize in her voice the tone of maternal adoration that dog owners adopt when addressing their pets.

Mavrik, the object of Trut's attention, is about the size of a Shetland sheepdog, with chestnut orange fur and a white bib down his front. He plays his designated role in turn: wagging his tail, rolling on his back, panting eagerly in anticipation of attention. In adjacent cages lining either side of the narrow, open-sided shed, dozens of canids do the same, yelping and clamoring in an explosion of fur and unbridled excitement. "As you can see," Trut says above the din, "all of them want human contact." Today, however, Mavrik is the lucky recipient. Trut reaches in and scoops him up, then hands him over to me. Cradled in my arms, gently jawing my hand in his mouth, he's as docile as any lapdog.

Except that Mavrik, as it happens, is not a dog at all. He's a fox. Hidden away on this overgrown property, flanked by birch forests and barred by a rusty metal gate, he and several hundred of his relatives are the only population of domesticated silver foxes in the world. (Most of them are, indeed, silver or dark gray; Mavrik is rare in his chestnut fur.) And by "domesticated" I don't mean captured and tamed, or raised by humans and conditioned by food to tolerate the occasional petting. I mean bred for domestication, as tame as your tabby cat or your Labrador. In fact, says Anna Kukekova, a Cornell researcher who studies the foxes, "they remind me a lot of golden retrievers, who are basically not aware that there are good people, bad people, people that they have met before, and those they haven't." These foxes treat any human as a potential companion, a behavior that is the product of arguably the most extraordinary breeding experiment ever conducted.

It started more than a half century ago, when Trut was still a graduate student. Led by a biologist named Dmitry Belyaev, researchers at the nearby Institute of Cytology and Genetics gathered up 130 foxes from fur farms. They then began breeding them with the goal of re-creating the evolution of wolves into dogs, a transformation that began more than 15,000 years ago.

With each generation of fox kits, Belyaev and his colleagues tested their reactions to human contact, selecting those most approachable to breed for the next generation. By the mid-1960s the experiment was working beyond what he could've imagined. They were producing foxes like Mavrik, not just unafraid of humans but actively seeking to bond with them. His team even repeated the experiment in two other species, mink and rats. "One huge thing that Belyaev showed was the timescale," says Gordon Lark, a University of Utah biologist who studies dog genetics. "If you told me the animal would now come sniff you at the front of the cage, I would say it's what I expect. But that they would become that friendly toward humans that quickly… wow."

Miraculously, Belyaev had compressed thousands of years of domestication into a few years. But he wasn't just looking to prove he could create friendly foxes. He had a hunch that he could use them to unlock domestication's molecular mysteries. Domesticated animals are known to share a common set of characteristics, a fact documented by Darwin in The Variation of Animals and Plants Under Domestication. They tend to be smaller, with floppier ears and curlier tails than their untamed progenitors. Such traits tend to make animals appear appealingly juvenile to humans. Their coats are sometimes spotted—piebald, in scientific terminology—while their wild ancestors' coats are solid. These and other traits, sometimes referred to as the domestication phenotype, exist in varying degrees across a remarkably wide range of species, from dogs, pigs, and cows to some non-mammalians like chickens, and even a few fish.

Belyaev suspected that as the foxes became domesticated, they too might begin to show aspects of a domestication phenotype. He was right again: Selecting which foxes to breed based solely on how well they got along with humans seemed to alter their physical appearance along with their dispositions. After only nine generations, the researchers recorded fox kits born with floppier ears. Piebald patterns appeared on their coats. By this time the foxes were already whining and wagging their tails in response to a human presence, behaviors never seen in wild foxes

Driving those changes, Belyaev postulated, was a collection of genes that conferred a propensity to tameness—a genotype that the foxes perhaps shared with any species that could be domesticated. Here on the fox farm, Kukekova and Trut are searching for precisely those genes today. Elsewhere, researchers are delving into the DNA of pigs, chickens, horses, and other domesticated species, looking to pinpoint the genetic differences that came to distinguish them from their ancestors. The research, accelerated by the recent advances in rapid genome sequencing, aims to answer a fundamental biological question: "How is it possible to make this huge transformation from wild animals into domestic animals?" says Leif Andersson, a professor of genome biology at Uppsala University, in Sweden. The answer has implications for understanding not just how we domesticated animals, but how we tamed the wild in ourselves as well.

The exercise of dominion over plants and animals is arguably the most consequential event in human history. Along with cultivated agriculture, the ability to raise and manage domesticated fauna—of which wolves were likely the first, but chickens, cattle, and other food species the most important—altered the human diet, paving the way for settlements and eventually nation-states to flourish. By putting humans in close contact with animals, domestication also created vectors for the diseases that shaped society.

Yet the process by which it all happened has remained stubbornly impenetrable. Animal bones and stone carvings can sometimes shed light on the when and where each species came to live side by side with humans. More difficult to untangle is the how. Did a few curious boar creep closer to human populations, feeding off their garbage and with each successive generation becoming a little more a part of our diet? Did humans capture red jungle fowl, the ancestor of the modern chicken, straight from the wild—or did the fowl make the first approach? Out of 148 large mammal species on Earth, why have no more than 15 ever been domesticated? Why have we been able to tame and breed horses for thousands of years, but never their close relative the zebra, despite numerous attempts? [Because they're from africa?]

In fact, scientists have even struggled to define domestication precisely. We all know that individual animals can be trained to exist in close contact with humans. A tiger cub fed by hand, imprinting on its captors, may grow up to treat them like family. But that tiger's offspring, at birth, will be just as wild as its ancestors. Domestication, by contrast, is not a quality trained into an individual, but one bred into an entire population through generations of living in proximity to humans. Many if not most of the species' wild instincts have long since been lost. Domestication, in other words, is mostly in the genes.

Yet the borders between domesticated and wild are often fluid. A growing body of evidence shows that historically, domesticated animals likely played a large part in their own taming, habituating themselves to humans before we took an active role in the process. "My working hypothesis," says Greger Larson, an expert on genetics and domestication at Durham University in the United Kingdom, "is that with most of the early animals—dogs first, then pigs, sheep, and goats—there was probably a long period of time of unintentional management by humans." The word domestication "implies something top down, something that humans did intentionally," he says. "But the complex story is so much more interesting."

The fox-farm experiment's role in unraveling that complexity is all the more remarkable for how it began. The Soviet biology establishment of the mid-20th century, led under Joseph Stalin by the infamous agronomist Trofim Lysenko, outlawed research into Mendelian genetics. But Dmitry Belyaev and his older brother Nikolay, both biologists, were intrigued by the possibilities of the science. "It was his brother's influence that caused him to have this special interest in genetics," Trut says of her mentor. "But these were the times when genetics was considered fake science." When the brothers flouted the prohibition and continued to conduct Mendelian-based studies, Belyaev lost his job as director of the Department of Fur Breeding. Nikolay's fate was more tragic: He was exiled to a labor camp, where he eventually died.

Secretly, Belyaev remained dedicated to genetic science, disguising his work as research in animal physiology. He was particularly consumed with the question of how such an incredible diversity of dogs could have arisen from their wolf ancestors. The answer, he knew, must lie at the molecular level. But even outside the Soviet Union, in the 1950s, the technology to sequence an animal's genome—and thereby try to understand how its genes had changed through history—was an impossible dream. So Belyaev decided to reproduce history himself. The silver fox, a fellow canid and close cousin of dogs that had never been domesticated, seemed the perfect choice.

Lyudmila Trut's first job as a grad student, in 1958, was to travel around to Soviet fur farms and select the calmest foxes she could find, to serve as the base population for Belyaev's experiment. The prohibition on genetic studies had thawed since Stalin's death in 1953, and Belyaev set up shop in Siberia at the newly minted Institute of Cytology and Genetics. Still, he was careful to frame the study only in terms of physiology, leaving out any mention of genes. Trut recalls that when Soviet leader Nikita Khrushchev arrived to inspect the institute, he was overheard to say, "What, are those geneticists still around? Were they not destroyed?" Protected by the careful politics of Belyaev's boss and favorable articles on genetics written by Khrushchev's journalist daughter, the fox-farm experiment quietly began.

By 1964 the fourth generation was already beginning to live up to the researchers' hopes. Trut can still remember the moment when she first saw a fox wag its tail at her approach. Before long, the most tame among them were so dog-like that they would leap into researchers' arms and lick their faces. At times the extent of the animals' tameness surprised even the researchers. Once, in the 1970s, a worker took one of the foxes home temporarily as a pet. When Trut visited him, she found the owner taking his fox for walks, unleashed, "just like a dog. I said 'Don't do that, we'll lose it, and it belongs to the institute!'" she recalls. "He said 'just wait,' then he whistled and said, 'Coca!' It came right back."

Simultaneously, more of the foxes began to show signs of the domestication phenotype: floppy ears retained longer in development and characteristic white spots on their coats. "At the beginning of the 1980s, we observed a kind of explosion-like change of the external appearance," says Trut. The research had expanded to include rats in 1972, followed by mink and—for a brief period—river otters. The otters proved difficult to breed and the experiment was eventually abandoned, but the scientists were able to shape the behavior of the other two species in parallel with the foxes.

Just as the genetic tools became available to accomplish Belyaev's end goal of tracing that connection to the animal's DNA, however, the project fell on hard times. With the collapse of the Soviet Union, scientific funds began to dwindle, and the researchers could do little more than keep the fox population alive. When Belyaev died of cancer in 1985, Trut took over the research and fought to keep it funded. But by the beginning of the 21st century, she was in danger of having to shut down the experiment.

Around the same time, Anna Kukekova, a Russian-born postdoc in molecular genetics at Cornell, read about the project's struggles. She had been fascinated with the fox-farm work for years, and now decided to focus her own research on the experiment. With help from Utah's Gordon Lark and a grant from the National Institutes of Health (NIH), she joined Trut's effort to try and finish what Belyaev had started.

Not all the foxes on the farm in Novosibirsk, it turns out, are as friendly as Mavrik. Across the small road from him and his fellow tame foxes is an identical-looking shed full of wire crates, each holding one of what the researchers refer to as the "aggressive foxes." To study the biology of tameness, the scientists needed to create a group of decidedly untame animals. So in a mirror image of the friendly foxes, the kits in the aggressive population are rated according to the hostility of their behavior. Only the most aggressive are bred for the next generation. Here are the evil twins of the tail-wagging Mavrik, straight out of a B-grade horror film: hissing, baring their teeth, snapping at the front of their cages when any human approaches.

"I'd like to draw your attention to this fox," says Trut, pointing to one snarling creature nearby. "You can see how aggressive she is. She was born to an aggressive mother but brought up by a tame mother." The switch, the result of the aggressive mother being unable to feed its kit, serendipitously proved a point: The foxes' response to humans is more nature than it is nurture. "Here," she says, "it's the genetics that change."

Identifying the precise genetic footprint involved in tameness, however, is proving extremely tricky science. First the researchers need to find the genes responsible for creating friendly and aggressive behaviors. Such general behavior traits, however, are actually amalgamations of more specific ones—fear, boldness, passivity, curiosity—that must be teased apart, measured, and traced to individual genes or sets of genes working in combination. Once those genes are identified, the researchers can test whether the ones influencing behavior are also behind the floppy ears and piebald coats and other features that characterize domesticated species. One theory among the scientists in Novosibirsk is that the genes guiding the animals' behavior do so by altering chemicals in their brains. Changes to those neurochemicals, in turn, have "downstream" impacts on the animals' physical appearance.

For now, though, Kukekova is focused on the first step: connecting tame behavior to genes. Toward the end of every summer, she travels from Cornell to Novosibirsk to evaluate the year's newborn kits. Each researcher's interaction with a kit is standardized and videotaped: opening a cage, reaching a hand in, touching the fox. Later, Kukekova reviews the tapes, using objective measures to quantify the foxes' postures, vocalizations, and other behaviors. Those data are layered on top of a pedigree—records that keep track of tame, aggressive, and "crossed" foxes (those with parents from each group).

The joint American-Russian research team then extracts DNA from blood samples of each fox in the study and scans for stark differences in the genomes of those that scored as aggressive or tame in the behavioral measures. In a paper in press in Behavior Genetics, the group reports finding two regions that are widely divergent in the two behavioral types and might thus harbor key domestication genes. Increasingly, it appears that domestication is driven not by a single gene but a suite of genetic changes. "Domestication," the paper concludes, "appears to be a very complex phenotype."

As it happens, 2,800 miles to the west in Leipzig, Germany, another laboratory is at the exact same juncture in understanding domestication genes in rats. Frank Albert, a researcher at the Max Planck Institute for Evolutionary Anthropology, obtained 30 descendants of Belyaev's rats (15 tame, 15 aggressive) in two wooden boxes from Siberia in 2004. "What we found were regions of the genome that influence tameness and aggression," says Albert. "But we don't know which genes cause these signals." Like Kukekova's group, he says, "we are in the process of whittling down the number."

Once either group is able to pinpoint one or more of the specific genetic pathways involved, they or other researchers can look for parallel genes in other domesticated species. "In a perfect situation, we'd like to define specific genes involved in tame and aggressive behaviors," says Kukekova. "Even when we find those, we will not know if they are the genes for domestication until we compare them in other animals."

Ultimately, the biggest payoff of the research may come from finding similar genes in the most thoroughly domesticated species of all: human beings. "Understanding what has changed in these animals is going to be incredibly informative," says Elaine Ostrander, of the National Human Genome Research Institute at NIH. "Everyone is waiting with great excitement for what they come out with."

Not all domestication researchers believe that Belyaev's silver foxes will unlock the secrets of domestication. Uppsala University's Leif Andersson, who studies the genetics of farm animals—and who lauds Belyaev and his fellow researchers' contribution to the field—believes that the relationship between tameness and the domestication phenotype may prove to be less direct than the fox study implies. "You select on one trait and you see changes in other traits," Andersson says, but "there has never been proven a causal relationship."

To understand how Andersson's view differs from that of the researchers in Novosibirsk, it's helpful to try and imagine how the two theories might have played out historically. Both would agree that the animals most likely to be domesticated were those predisposed to human contact. Some mutation, or collection of mutations, in their DNA caused them to be less afraid of humans, and thus willing to live closer to them. Perhaps they fed off human refuse or benefited from inadvertent shelter from predators. At some point humans saw some benefit in return from these animal neighbors and began helping that process along, actively selecting for the most amenable ones and breeding them. "At the beginning of the domestication process, only natural selection was at work," as Trut puts it. "Down the road, this natural selection was replaced with artificial selection."

Where Andersson differs is in what happened next. If Belyaev and Trut are correct, the self-selection and then human selection of less fearful animals carried with it other components of the domestication phenotype, such as curly tails and smaller bodies. In Andersson's view, that theory understates the role humans played in selecting those other traits. Sure, curiosity and lack of fear may have started the process, but once animals were under human control, they were also protected from wild predators. Random mutations for physical traits that might quickly have been weeded out in the wild, like white spots on a dark coat, were allowed to persist. Then they flourished, in part because, well, people liked them. "It wasn't that the animals behaved differently," as Andersson says, "it's just that they were cute."

In 2009 Andersson bolstered his theory by comparing mutations in coat-color genes between several varieties of domesticated and wild pigs. The results, he reported, "demonstrate that early farmers intentionally selected pigs with novel coat coloring. Their motivations could have been as simple as a preference for the exotic or selection for reduced camouflage."

In his own hunt for domestication genes, Andersson is taking a close look at the most populous domesticated animal on Earth: the chicken. Their ancestors, red jungle fowl, roamed freely in the jungles of India, Nepal, and other parts of South and Southeast Asia. Somewhere around 8,000 years ago, humans started breeding them for food. Last year Andersson and his colleagues compared the full genomes of domesticated chickens with those of zoo-based populations of red jungle fowl. They identified a mutation, in a gene known as TSHR, that was found only in domestic populations. The implication is that TSHR thereby played some role in domestication, and now the team is working to determine exactly what the TSHR mutation controls. Andersson hypothesizes that it could play a role in the birds' reproductive cycles, allowing chickens to breed more frequently in captivity than red jungle fowl do in the wild—a trait early farmers would have been eager to perpetuate. The same difference exists between wolves, which reproduce once a year and in the same season, and dogs, which can breed multiple times a year, in any season.

If Andersson's theory is correct, it may turn out to have intriguing implications for our own species. Harvard biologist Richard Wrangham has theorized that we, too, went through a domestication process that altered our biology. "The question of what is the difference between the domestic pig and a wild boar, or the distinction between a broiler chicken and a wild jungle fowl," Andersson told me, "is very similar to the question of what is the difference between a human and a chimpanzee?" [Answer: The mediterranean sea.]

Human beings are not simply domesticated chimpanzees, but understanding the genetics of domestication in chickens, dogs, and pigs may still tell us a surprising amount about the sources of our own social behavior. That's one reason the fox-farm research being conducted by Kukekova is underwritten by the NIH. "There are over 14,000 genes expressed in the brain, and not many are understood," she points out. Ferreting out which of those genes are related to social behavior is a tricky business; obviously one cannot perform breeding experiments on humans, and studies purporting to find innate differences in behavior among people or populations are at the very least problematic.

But delving into the DNA of our closest companions can deliver some tantalizing insights. In 2009 UCLA biologist Robert Wayne led a study comparing the wolf and dog genomes. The finding that made headlines was that dogs originated from gray wolves not in East Asia, as other researchers had argued, but in the Middle East. Less noticed by the press was a brief aside in which Wayne and his colleagues identified a particular short DNA sequence, located near a gene called WBSCR17, that was very different in the two species. That region of the genome, they suggested, could be a potential target for "genes that are important in the early domestication of dogs." In humans, the researchers went on to note, WBSCR17 is at least partly responsible for a rare genetic disorder called Williams-Beuren syndrome. Williams-Beuren is characterized by elfin features, a shortened nose bridge, and "exceptional gregariousness"—its sufferers are often overly friendly and trusting of strangers.

After the paper was published, Wayne says, "the number one email we got was from parents of children suffering from Williams-Beuren. They said, Actually our children remind us of dogs in terms of their ability to read behavior and their lack of social barriers in their behavior." The elfin traits also seemed to correspond to aspects of the domestication phenotype. Wayne cautions against making one-to-one parallels between domestication genes and something as genetically complex as Williams-Beuren. The researchers are "intrigued," he says, and hoping to explore the connection further.

In 2003 a young researcher at Duke University named Brian Hare travelled out to Novosibirsk. Hare is known for his work cataloguing the unique behaviors of dogs and wolves, showing the ways in which dogs have evolved to follow human cues like pointing and eye movements. When he conducted similar tests on fox kits in Siberia, he found that they did just as well as puppies of the same age. The results, while preliminary, suggest that selecting against fear and aggression—what Hare calls "emotional reactivity"—has created foxes that are not just tame but that also have the dog-like ability to engage with humans using their social cues.

"They didn't select for a smarter fox but for a nice fox," says Hare. "But they ended up getting a smart fox." This research also has implications for the origins of human social behavior. "Are we domesticated in the sense of dogs? No. But I am comfortable saying that the first thing that has to happen to get a human from an apelike ancestor is a substantial increase in tolerance toward one another. There had to be a change in our social system."

Hare's research came to mind on my last afternoon in Novosibirsk, as Kukekova, my translator Luda Mekertycheva, and I played with Mavrik in a pen behind the fox farm's research house. We watched him chase a ball and wrestle with another fox, then run back so we could grab him up and let him lick our faces. But we all had flights to catch, and after an hour, Kukekova carried him back toward the sheds. Mavrik seemed to sense that he was headed back to his cage and whined with increasing agitation. Here was an animal biologically conditioned for human attention, as much as any dog is. Now that we'd provided it, I suddenly felt guilty for taking it away.

The fox-farm experiment is, of course, just that: a scientific experiment. For decades the project has been forced to manage their population by selling off to real fur farms those foxes not friendly or aggressive enough to be research candidates. For the scientists, deciding which ones stay and which ones go is a harrowing process; Trut says she has long since passed on the job to others and stays away from the farm during selection time. "It is very difficult emotionally," she told me.

In recent years the institute has been working to obtain permits to sell the surplus tame foxes as pets, both domestically and in other countries. It would be a way not just to find a better home for the unwanted foxes, they suggest, but also to raise money for the research to continue. "The situation today is we are just doing our best to preserve our population," Trut says. "We do some genetic work with our partners in America. But this experiment has many more questions to resolve."

As for Mavrik, Luda Mekertycheva was so enthralled by the chestnut-colored fox and another playmate that she decided to adopt them. They arrived at her dacha outside of Moscow a few months later, and not long after, she emailed me an update. "Mavrik and Peter jump on my back when I kneel to give them food, sit when I pet them, and take vitamins from my hand," she wrote. "I love them a lot."



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Old July 17th, 2012 #2
Crowe
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I have seen domesticated coons (4 legged variety), pot bellied pigs, as well as possums and coyotes. Find them when they are babies, and raise them up. Its possible to domesticate pretty much any Mammal, even many that would normally prey on humans in the wild. I remember when I was a kid we had a neighbor that had a pet coon, and the lady treated it like it was a cat, and she even fed it cat food. It was friendly to humans, it would let you pet it and even roll on its back so you could rub its belly.
 
Old July 17th, 2012 #3
Steven L. Akins
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Quote:
Originally Posted by Crowe View Post
I have seen domesticated coons (4 legged variety), pot bellied pigs, as well as possums and coyotes. Find them when they are babies, and raise them up. Its possible to domesticate pretty much any Mammal, even many that would normally prey on humans in the wild. I remember when I was a kid we had a neighbor that had a pet coon, and the lady treated it like it was a cat, and she even fed it cat food. It was friendly to humans, it would let you pet it and even roll on its back so you could rub its belly.
Here's a coon with a pet coon:

(The older of the two coons was an old slave that belonged to my great-great-great-uncle, John T. Akins)



 
Old July 17th, 2012 #4
MikeTodd
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Originally Posted by Steven L. Akins View Post
Here's a coon with a pet coon:

(The older of the two coons was an old slave that belonged to my great-great-great-uncle, John T. Akins)



The raccoon has existed in North America longer than most negros.
I once found a raccoon scavenging through my garbage cans in the early morning hours.

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Raccoon
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For other species called raccoon in the genus Procyon, see Procyon (genus). For other uses, see Raccoon (disambiguation).
Raccoon
Conservation status

Least Concern (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Procyonidae
Genus: Procyon
Species: P. lotor
Binomial name
Procyon lotor
(Linnaeus, 1758)
Range map of raccoon
Synonyms

Ursus lotor Linnaeus, 1758

The raccoon Listeni/ræˈkuːn/, Procyon lotor (sometimes spelled racoon[2]), also known as the common raccoon,[3] North American raccoon,[4] northern raccoon[5] and colloquially as coon,[6] is a medium-sized mammal native to North America. It is the largest of the procyonid family, having a body length of 40 to 70 cm (16 to 28 in) and a body weight of 3.5 to 9 kg (8 to 20 lb). The raccoon is usually nocturnal and is omnivorous, with a diet consisting of about 40% invertebrates, 33% plant foods, and 27% vertebrates. It has a grayish coat, of which almost 90% is dense underfur, which insulates against cold weather. Two of its most distinctive features are its extremely dexterous front paws and its facial mask, which are themes in the mythology of several Native American tribes. Raccoons are noted for their intelligence, with studies showing that they are able to remember the solution to tasks up to three years later.

The original habitats of the raccoon are deciduous and mixed forests of North America, but due to their adaptability they have extended their range to mountainous areas, coastal marshes, and urban areas, where many homeowners consider them to be pests. As a result of escapes and deliberate introductions in the mid-20th century, raccoons are now also distributed across the European mainland, the Caucasus region and Japan.

Though previously thought to be solitary, there is now evidence that raccoons engage in gender-specific social behavior. Related females often share a common area, while unrelated males live together in groups of up to four animals to maintain their positions against foreign males during the mating season, and other potential invaders. Home range sizes vary anywhere from 3 hectares for females in cities to 50 km2 for males in prairies (7 acres to 20 sq mi). After a gestation period of about 65 days, two to five young, known as "kits", are born in spring. The kits are subsequently raised by their mother until dispersion in late fall. Although captive raccoons have been known to live over 20 years, their average life expectancy in the wild is only 1.8 to 3.1 years. In many areas, hunting and vehicular injury are the two most common causes of death.
Magical Mystery Tour; the soundtrack to a forthcoming Beatles television film, was released in the UK as a six-track double extended play disc (EP) in early December 1967.[74][185] In the United States, the six songs were iss
Etymology
The mask of a raccoon is often interrupted by a brown-black streak that extends from forehead to nose.[7]

The word "raccoon" was adopted into English from the native Powhatan term, as used in the Virginia Colony. It was recorded on Captain John Smith's list of Powhatan words as aroughcun, and on that of William Strachey as arathkone. It has also been identified as a Proto-Algonquian root *ahrah-koon-em, meaning "[the] one who rubs, scrubs and scratches with its hands".[8]

Similarly, Spanish colonists adopted the Spanish word mapache from the Nahuatl mapachitli of the Aztecs, meaning "[the] one who takes everything in its hands".[9] In many languages, the raccoon is named for its characteristic dousing behavior in conjunction with that language's term for bear, for example Waschbär in German, orsetto lavatore in Italian, mosómedve in Hungarian and araiguma (アライグマ) in Japanese. In French and Portuguese (in Portugal), the washing behavior is combined with these languages' term for rat, yielding, respectively, raton laveur and ratão-lavadeiro.

The colloquial abbreviation coon is used in words like coonskin for fur clothing and in phrases like old coon as a self-designation of trappers.[10] However, the clipped form is also in use as an ethnic slur.[11] The raccoon's scientific name, Procyon lotor, is neo-Latin, meaning "before-dog washer", with lotor Latin for "washer" and Procyon Latinized Greek from προ-, "before" and κύων, "dog".
Taxonomy

In the first decades after its discovery by the members of the expedition of Christopher Columbus – the first person to leave a written record about the species – taxonomists thought the raccoon was related to many different species, including dogs, cats, badgers and particularly bears.[12] Carl Linnaeus, the father of modern taxonomy, placed the raccoon in the genus Ursus, first as Ursus cauda elongata ("long-tailed bear") in the second edition of his Systema Naturae (1740), then as Ursus Lotor ("washer bear") in the tenth edition (1758–59).[13] In 1780, Gottlieb Conrad Christian Storr placed the raccoon in its own genus Procyon, which can be translated as either "before the dog" or "doglike".[14] It is also possible that Storr had its nocturnal lifestyle in mind and chose the star Procyon as eponym for the species.[15]
Evolution

Based on fossil evidence from France and Germany, the first known members of the family Procyonidae lived in Europe in the late Oligocene about 25 million years ago.[16] Similar tooth and skull structures suggest procyonids and weasels share a common ancestor, but molecular analysis indicates a closer relationship between raccoons and bears.[17] After the then-existing species crossed the Bering Strait at least six million years later, the center of its distribution was probably in Central America.[18] Coatis (Nasua and Nasuella) and raccoons (Procyon) have been considered to possibly share common descent from a species in the genus Paranasua present between 5.2 and 6.0 million years ago.[19] This assumption, based on morphological comparisons, conflicts with a 2006 genetic analysis which indicates raccoons are more closely related to ringtails.[20] Unlike other procyonids, such as the crab-eating raccoon (Procyon cancrivorus), the ancestors of the common raccoon left tropical and subtropical areas and migrated farther north about 4 million years ago, in a migration that has been confirmed by the discovery in the Great Plains of fossils dating back to the middle of the Pliocene.[21]
Subspecies

Four subspecies of raccoon endemic to small Central American and Caribbean islands were often regarded as distinct species after their discovery. These are the Bahaman raccoon and Guadeloupe raccoon, which are very similar to each other; the Tres Marias raccoon, which is larger than average and has an angular skull; and the extinct Barbados raccoon. Studies of their morphological and genetic traits in 1999, 2003 and 2005 led all these island raccoons to be listed as subspecies of the common raccoon in the third edition of Mammal Species of the World (2005).[22][23][24][25] A fifth island raccoon population, the Cozumel raccoon, which weighs only 3 to 4 kg (6.6 to 8.8 lb) and has notably small teeth, is still regarded as a separate species.

The four smallest raccoon subspecies, with an average weight of 2 to 3 kilograms (4.4 to 6.6 lb), are found along the southern coast of Florida and on the adjacent islands; an example is the Ten Thousand Island raccoon (Procyon lotor marinus).[26] Most of the other 15 subspecies differ only slightly from each other in coat color, size and other physical characteristics.[27] The two most widespread subspecies are the eastern raccoon (Procyon lotor lotor) and the upper Mississippi Valley raccoon (Procyon lotor hirtus). Both share a comparatively dark coat with long hairs, but the upper Mississippi Valley raccoon is larger than the eastern raccoon. The eastern raccoon occurs in all US states and Canadian provinces to the north of South Carolina and Tennessee. The adjacent range of the upper Mississippi Valley raccoon covers all US states and Canadian provinces to the north of Louisiana, Texas and New Mexico.[28]
Description
Physical characteristics
An albino specimen in Virginia Key, Florida
Skull with dentition: 2/2 molars, 4/4 premolars, 1/1 canines, 3/3 incisors
Raccoon skeleton

Head to hindquarters, raccoons measure between 40 and 70 cm (16 and 28 in), not including the bushy tail which can measure between 20 and 40 cm (8 and 16 in), but is usually not much longer than 25 cm (10 in).[29] The shoulder height is between 23 and 30 cm (9 and 12 in).[30] The skull of the adult male measures 94.3–125.8 mm long and 60.2–89.1 mm wide, while that of the female measures 89.4–115.9 mm long and 58.3–81.2 mm wide.[31] The body weight of an adult raccoon varies considerably with habitat; it can range from 2 to 14 kilograms (4 to 30 lb), but is usually between 3.5 and 9 kilograms (8 and 20 lb). The smallest specimens are found in Southern Florida, while those near the northern limits of the raccoon's range tend to be the largest (see Bergmann's rule).[32] Males are usually 15 to 20% heavier than females.[33] At the beginning of winter, a raccoon can weigh twice as much as in spring because of fat storage.[34] It is one of the most variably sized of all mammals. The largest recorded wild raccoon weighed 28.4 kg (62.6 lb) and measured 140 cm (55 in) in total length, by far the largest size recorded for a procyonid.[35][36]

The most characteristic physical feature of the raccoon is the area of black fur around the eyes, which contrasts sharply with the surrounding white face coloring. This is reminiscent of a "bandit's mask" and has thus enhanced the animal's reputation for mischief.[37] The slightly rounded ears are also bordered by white fur. Raccoons are assumed to recognize the facial expression and posture of other members of their species more quickly because of the conspicuous facial coloration and the alternating light and dark rings on the tail. The rings resemble those of a ringtail lemur.[38][39] The dark mask may also reduce glare and thus enhance night vision.[39] On other parts of the body, the long and stiff guard hairs, which shed moisture, are usually colored in shades of gray and, to a lesser extent, brown.[40] Raccoons with a very dark coat are more common in the German population because individuals with such coloring were among those initially released to the wild.[41] The dense underfur, which accounts for almost 90% of the coat, insulates against cold weather and is composed of 2 to 3 cm (0.8 to 1.2 in) long hairs.[40]
Raccoon baculum or "penis bone"

The raccoon, whose method of locomotion is usually considered to be plantigrade, can stand on its hind legs to examine objects with its front paws.[42] As raccoons have short legs compared to their compact torso, they are usually not able either to run quickly or jump great distances.[43] Their top speed over short distances is 16 to 24 km/h (10 to 15 mph).[44][45] Raccoons can swim with an average speed of about 5 km/h (3 mph) and can stay in the water for several hours.[46] For climbing down a tree headfirst—an unusual ability for a mammal of its size—a raccoon rotates its hind feet so they are pointing backwards.[47] Raccoons have a dual cooling system to regulate their temperature; that is, they are able to both sweat and pant for heat dissipation.[48]

Raccoon skulls have a short and wide facial region and a voluminous braincase. The facial length of the skull is less than the cranial, and their nasal bones are short and quite broad. The auditory bullae are inflated in form, and the sagittal crest is weakly developed.[49] The dentition — 40 teeth with the dental formula: Upper: 3.1.4.2, lower: 3.1.4.2 — is adapted to their omnivorous diet: the carnassials are not as sharp and pointed as those of a full-time carnivore, but the molars are not as wide as those of a herbivore.[50] The penis bone of males is about 10 cm (4 in) long and strongly bent at the front end and is often used by biologists to classify reproductive status of specimens.[51] Seven of the thirteen identified vocal calls are used in communication between the mother and her kits, one of these being the birdlike twittering of newborns.[52]
Senses
Bottom side of the front paw with visible vibrissae on the tips of the digits

The most important sense for the raccoon is its sense of touch.[53] The "hyper sensitive"[54] front paws are protected by a thin horny layer which becomes pliable when wet.[55] The five digits of the paws have no webbing between them, which is unusual for a carnivoran.[56] Almost two-thirds of the area responsible for sensory perception in the raccoon's cerebral cortex is specialized for the interpretation of tactile impulses, more than in any other studied animal.[57] They are able to identify objects before touching them with vibrissae located above their sharp, nonretractable claws.[58] The raccoon's paws lack an opposable thumb and thus it does not have the agility of the hands of primates.[59] There is no observed negative effect on tactile perception when a raccoon stands in water below 10 °C (50 °F) for hours.[60]

Raccoons are thought to be color blind or at least poorly able to distinguish color, though their eyes are well-adapted for sensing green light.[61] Although their accommodation of 11 dioptre is comparable to that of humans and they see well in twilight because of the tapetum lucidum behind the retina, visual perception is of subordinate importance to raccoons because of their poor long-distance vision.[62] In addition to being useful for orientation in the dark, their sense of smell is important for intraspecific communication. Glandular secretions (usually from their anal glands), urine and feces are used for marking.[63] With their broad auditory range, they can perceive tones up to 50–85 kHz as well as quiet noises like those produced by earthworms underground.[64]
Intelligence

Only a few studies have been undertaken to determine the mental abilities of raccoons, most of them based on the animal's sense of touch. In a study by the ethologist H. B. Davis in 1908, raccoons were able to open 11 of 13 complex locks in less than 10 tries and had no problems repeating the action when the locks were rearranged or turned upside down. Davis concluded they understood the abstract principles of the locking mechanisms and their learning speed was equivalent to that of rhesus macaques.[65] Studies in 1963, 1973, 1975 and 1992 concentrated on raccoon memory showed they can remember the solutions to tasks for up to three years.[66] In a study by B. Pohl in 1992, raccoons were able to instantly differentiate between identical and different symbols three years after the short initial learning phase.[66] Stanislas Dehaene reports in his book The Number Sense raccoons can distinguish boxes containing two or four grapes from those containing three.[67]
Behavior
Social behavior
Raccoons in a tree: The raccoon's social structure is grouped into what Ulf Hohmann calls a "three class society".

Studies in the 1990s by the ethologists Stanley D. Gehrt and Ulf Hohmann indicated raccoons engage in gender-specific social behaviors and are not typically solitary, as was previously thought.[68][69] Related females often live in a so-called "fission-fusion society", that is, they share a common area and occasionally meet at feeding or resting grounds.[70] Unrelated males often form loose male social groups to maintain their position against foreign males during the mating season—or against other potential invaders.[71] Such a group does not usually consist of more than four individuals.[72] Since some males show aggressive behavior towards unrelated kits, mothers will isolate themselves from other raccoons until their kits are big enough to defend themselves.[73] With respect to these three different modes of life prevalent among raccoons, Hohmann called their social structure a "three class society".[74] Samuel I. Zeveloff, professor of zoology at Weber State University and author of the book Raccoons: A Natural History, is more cautious in his interpretation and concludes at least the females are solitary most of the time and, according to Erik K. Fritzell's study in North Dakota in 1978, males in areas with low population densities are solitary, as well.[75]

The shape and size of a raccoon's home range varies depending on age, gender, and habitat, with adults claiming areas more than twice as large as juveniles.[76] While the size of home ranges in the inhospitable habitat of North Dakota's prairies lay between 7 and 50 km2 (3 and 20 sq mi) for males and between 2 and 16 km2 (1 and 6 sq mi) for females, the average size in a marsh at Lake Erie was 0.49 km2 (0.19 sq mi).[77] Irrespective of whether the home ranges of adjacent groups overlap, they are most likely not actively defended outside the mating season if food supplies are sufficient.[78] Odor marks on prominent spots are assumed to establish home ranges and identify individuals.[79] Urine and feces left at shared latrines may provide additional information about feeding grounds, since raccoons were observed to meet there later for collective eating, sleeping and playing.[80]

Concerning the general behavior patterns of raccoons, Gehrt points out, "typically you'll find 10 to 15 percent that will do the opposite"[81] of what is expected.
Diet

Though usually nocturnal, the raccoon is sometimes active in daylight to take advantage of available food sources.[82] Its diet consists of about 40% invertebrates, 33% plant material and 27% vertebrates.[83] Since its diet consists of such a variety of different foods, Zeveloff argues the raccoon "may well be one of the world's most omnivorous animals".[84] While its diet in spring and early summer consists mostly of insects, worms, and other animals already available early in the year, it prefers fruits and nuts, such as acorns and walnuts, which emerge in late summer and autumn, and represent a rich calorie source for building up fat needed for winter.[85] They eat active or large prey, such as birds and mammals, only occasionally, since they prefer prey that is easier to catch, specifically fish and amphibians.[86] Bird nests (eggs and hatchlings) are frequently preyed on, and small birds are often helpless to defend against the attacking raccoon.[87] When food is plentiful, raccoons can develop strong individual preferences for specific foods.[88] In the northern parts of their range, raccoons go into a winter rest, reducing their activity drastically as long as a permanent snow cover makes searching for food impossible.[89]
Dousing
Captive raccoons often douse their food before eating.

Raccoons sample food and other objects with their front paws to examine them and to remove unwanted parts. The tactile sensitivity of their paws is increased if this action is performed underwater, since the water softens the hard layer covering the paws.[90] However, the behavior observed in captive raccoons in which they carry their food to a watering hole to "wash" or douse it before eating has not been observed in the wild.[91] Naturalist Georges-Louis Leclerc, Comte de Buffon (1707–1788) believed that raccoons do not have adequate saliva production to moisten food, necessitating dousing, but this is certainly incorrect.[92] Captive raccoons douse their food more frequently when a watering hole with a layout similar to a stream is not farther away than 3 m (10 ft).[93] The widely accepted theory is that dousing is a vacuum activity imitating foraging at shores for aquatic foods.[94] This is supported by the observation that such foods are doused more frequently. Cleaning dirty food does not seem to be a reason for "washing".[93] Experts have cast doubt on the veracity of observations of wild raccoons dousing food.[95]
Reproduction

Raccoons usually mate in a period triggered by increasing daylight between late January and mid-March.[96] However, there are large regional differences which are not completely explicable by solar conditions. For example, while raccoons in southern states typically mate later than average, the mating season in Manitoba also peaks later than usual in March and extends until June.[97] During the mating season, males roam their home ranges in search of females in an attempt to court them during the three to four day period when conception is possible. These encounters will often occur at central meeting places.[98] Copulation, including foreplay, can last over an hour and is repeated over several nights.[99] The weaker members of a male social group also are assumed to get the opportunity to mate, since the stronger ones cannot mate with all available females.[100] In a study in southern Texas during the mating seasons from 1990 to 1992, about one third of all females mated with more than one male.[101] If a female does not become pregnant or if she loses her kits early, she will sometimes become fertile again 80 to 140 days later.[102]
A kit

After usually 63 to 65 days of gestation (although anywhere from 54 to 70 days is possible), a litter of typically two to five young is born.[103] The average litter size varies widely with habitat, ranging from 2.5 in Alabama to 4.8 in North Dakota.[104] Larger litters are more common in areas with a high mortality rate, due, for example, to hunting or severe winters.[105] While male yearlings usually reach their sexual maturity only after the main mating season, female yearlings can compensate for high mortality rates and may be responsible for about 50% of all young born in a year.[106] Males have no part in raising young.[107] The kits (also called "cubs") are blind and deaf at birth, but their mask is already visible against their light fur.[108] The birth weight of the about 10 cm (4 in)-long kits is between 60 and 75 g (2.1 and 2.6 oz).[109] Their ear canals open after around 18 to 23 days, a few days before their eyes open for the first time.[110] Once the kits weigh about 1 kg (2 lb), they begin to explore outside the den, consuming solid food for the first time after six to nine weeks.[111] After this point, their mother suckles them with decreasing frequency; they are usually weaned by 16 weeks.[112] In the fall, after their mother has shown them dens and feeding grounds, the juvenile group splits up.[113] While many females will stay close to the home range of their mother, males can sometimes move more than 20 km (12 mi) away.[114] This is considered an instinctive behavior, preventing inbreeding.[115] However, mother and offspring may share a den during the first winter in cold areas.[116]
Life expectancy
Raccoon in Bear Country USA.ogg
Captive raccoons like this one in Bear Country USA are known to live for more than 20 years.

Captive raccoons have been known to live for more than 20 years.[117] However, the species' life expectancy in the wild is only 1.8 to 3.1 years, depending on the local conditions in terms of traffic volume, hunting, and weather severity.[118] It is not unusual for only half of the young born in one year to survive a full year.[119] After this point, the annual mortality rate drops to between 10% and 30%.[120] Young raccoons are vulnerable to losing their mother and to starvation, particularly in long and cold winters.[121] The most frequent natural cause of death in the North American raccoon population is distemper, which can reach epidemic proportions and kill most of a local raccoon population.[122] In areas with heavy vehicular traffic and extensive hunting, these factors can account for up to 90% of all deaths of adult raccoons.[123]

The most important natural predators of the raccoon are bobcats, coyotes, and great horned owls, the latter mainly preying on young raccoons. In the Chesapeake Bay, raccoons are the most important mammalian prey for bald eagles.[124] In their introduced range in the former Soviet Union, their main predators are wolves, lynxes and eagle owls.[125] However, predation is not a significant cause of death, especially because larger predators have been exterminated in many areas inhabited by raccoons.[126]
Range
Habitat
Taking refuge in a tree, Ottawa, Ontario

Although they have thrived in sparsely wooded areas in the last decades, raccoons depend on vertical structures to climb when they feel threatened.[127] Therefore, they avoid open terrain and areas with high concentrations of beech trees, as beech bark is too smooth to climb.[128] Tree hollows in old oaks or other trees and rock crevices are preferred by raccoons as sleeping, winter and litter dens. If such dens are unavailable or accessing them is inconvenient, raccoons use burrows dug by other mammals, dense undergrowth, roadside culverts in urban areas, or tree crotches.[129] In a study in the Solling range of hills in Germany, more than 60% of all sleeping places were used only once, but those used at least ten times accounted for about 70% of all uses.[130] Since amphibians, crustaceans, and other animals found around the shore of lakes and rivers are an important part of the raccoon's diet, lowland deciduous or mixed forests abundant with water and marshes sustain the highest population densities.[131] While population densities range from 0.5 to 3.2 animals per square kilometre (0.2 – 1.2 animals per square mile) in prairies and do not usually exceed 6 animals per square kilometer (2.3 animals per square mile) in upland hardwood forests, more than 20 raccoons per square kilometer (50 animals per square mile) can live in lowland forests and marshes.[132]
Distribution in North America

Raccoons are common throughout North America from Canada to Panama, where the subspecies P. l. pumilus coexists with the crab-eating Raccoon (P. cancrivorus).[133] The population on Hispaniola was exterminated as early as 1513 by Spanish colonists who hunted them for their meat.[134] Raccoons were also exterminated in Cuba and Jamaica, where the last sightings were reported in 1687.[135] The Bahaman raccoon (P. l. maynardi) was classified as endangered by the IUCN in 1996.[136]
racoon
Racoon in the middle of the night looking for food (Sierra-Nevada Mountains, California)

There is evidence that in pre-Columbian times raccoons were numerous only along rivers and in the woodlands of the Southeastern United States.[137] As raccoons were not mentioned in earlier reports of pioneers exploring the central and north-central parts of the United States,[138] their initial spread may have begun a few decades before the 20th century. Since the 1950s, raccoons have expanded their range from Vancouver Island—formerly the northernmost limit of their range—far into the northern portions of the four south-central Canadian provinces.[139] New habitats which have recently been occupied by raccoons (aside from urban areas) include mountain ranges, such as the Western Rocky Mountains, prairies and coastal marshes.[140] After a population explosion starting in the 1940s, the estimated number of raccoons in North America in the late 1980s was 15 to 20 times higher than in the 1930s, when raccoons were comparatively rare.[141] Urbanization, the expansion of agriculture, deliberate introductions, and the extermination of natural predators of the raccoon have probably caused this increase in abundance and distribution.[142]
Distribution outside North America
Distribution in Germany: Raccoons killed or found dead by hunters in the hunting years 2000/01, 01/02 and 02/03 in the administrative districts of Germany

As a result of escapes and deliberate introductions in the mid-20th century, the raccoon is now distributed in several European and Asian countries. Sightings have occurred in all the countries bordering Germany, which hosts the largest population outside of North America.[143] Another stable population exists in northern France, where several pet raccoons were released by members of the U.S. Air Force near the Laon-Couvron Air Base in 1966.[144] About 1,240 animals were released in nine regions of the former Soviet Union between 1936 and 1958 for the purpose of establishing a population to be hunted for their fur. Two of these introductions were successful: one in the south of Belarus between 1954 and 1958, and another in Azerbaijan between 1941 and 1957. With a seasonal harvest of between 1,000 and 1,500 animals, in 1974 the estimated size of the population distributed in the Caucasus region was around 20,000 animals and the density was four animals per square kilometer (10 animals per square mile).[145]
Distribution in Germany

On April 12, 1934, two pairs of pet raccoons were released into the German countryside at the Edersee reservoir in the north of Hesse by forest superintendent Wilhelm Freiherr Sittich von Berlepsch, upon request of their owner, the poultry farmer Rolf Haag.[146] He released them two weeks before receiving permission from the Prussian hunting office to "enrich the fauna", as Haag's request stated.[147] Several prior attempts to introduce raccoons in Germany were not successful.[148] A second population was established in East Germany in 1945 when 25 raccoons escaped from a fur farm at Wolfshagen east of Berlin after an air strike. The two populations are parasitologically distinguishable: 70% of the raccoons of the Hessian population are infected with the roundworm Baylisascaris procyonis, but none of the Brandenburgian population has the parasite.[149] The estimated number of raccoons was 285 animals in the Hessian region in 1956, over 20,000 animals in the Hessian region in 1970 and between 200,000 and 400,000 animals in the whole of Germany in 2008.[122][150]

The raccoon was a protected species in Germany, but has been declared a game animal in 14 states since 1954.[151] Hunters and environmentalists argue the raccoon spreads uncontrollably, threatens protected bird species and supersedes domestic carnivorans.[41] This view is opposed by the zoologist Frank-Uwe Michler, who finds no evidence a high population density of raccoons has negative effects on the biodiversity of an area.[41] Hohmann holds extensive hunting cannot be justified by the absence of natural predators, because predation is not a significant cause of death in the North American raccoon population.[152]
Distribution in the former USSR

Experiments in acclimatising raccoons into the USSR began in 1936, and were repeated a further 25 times until 1962. Overall, 1,222 individuals were released, 64 of which came from zoos and fur farms (38 of them having been imports from western Europe). The remainder originated from a population previously established in Transcaucasia. The range of Soviet raccoons was never single or continuous, as they were often introduced to different locations far from each other. All introductions into the Russian Far East failed ; melanistic raccoons were released on Petrov Island near Vladivostok and some areas of southern Primorsky Krai, but died. In Middle Asia, raccoons were released in Kyrgyzstan's Jalal-Abad Province, though they were later recorded as "practically absent" there in January 1963. A large and stable raccoon population (yielding 1000–1500 catches a year) was established in Azerbaijan after an introduction to the area in 1937. Raccoons apparently survived an introduction near Terek, along the Sulak River into the Dagestani lowlands. Attempts to settle racoons on the Kuban River's left tributary and Kabardino-Balkaria were unsuccessful. A successful acclimatization occurred in Belarus, where three introductions (consisting of 52, 37 and 38 individuals in 1954 and 1958) took place. By January 1, 1963, 700 individuals were recorded in the country.[153]
Distribution in Japan

In Japan, up to 1,500 raccoons were imported as pets each year after the success of the anime series Rascal the Raccoon (1977). In 2004, the descendants of discarded or escaped animals lived in 42 of 47 prefectures.[154][155][156] In Japan, it competes as a wild animal alongside the indigenous raccoon dog (tanuki), a wild canid with a similar lifestyle and visual characteristics.[156]
Urban raccoons
On the roof of a house in Albertshausen, Germany

Due to its adaptability, the raccoon has been able to use urban areas as a habitat. The first sightings were recorded in a suburb of Cincinnati in the 1920s. Since the 1950s, raccoons have been present in Philadelphia, Washington, DC, New York City, Chicago, San Francisco, Los Angeles, and Toronto.[157] Since the 1960s, Kassel has hosted Europe's first and densest population in a large urban area, with about 50 to 150 animals per square kilometre (130–400 animals per square mile), a figure comparable to those of urban habitats in North America.[157][158] Home range sizes of urban raccoons are only three to 40 hectares (7.5–100 acres) for females and eight to 80 hectares (20–200 acres) for males.[159] In small towns and suburbs, many raccoons sleep in a nearby forest after foraging in the settlement area.[157][160] Fruit and insects in gardens and leftovers in municipal waste are easily available food sources.[161] Furthermore, a large number of additional sleeping areas exist in these areas, such as hollows in old garden trees, cottages, garages, abandoned houses, and attics. The percentage of urban raccoons sleeping in abandoned or occupied houses varies from 15% in Washington, DC (1991) to 43% in Kassel (2003).[162]
Health
Baylisascaris procyonis larvae

Raccoons can carry rabies, a lethal disease caused by the neurotropic rabies virus carried in the saliva and transmitted by bites. Its spread began in Florida and Georgia in the 1950s and was facilitated by the introduction of infected individuals to Virginia and North Dakota in the late 1970s.[163] Of the 6,940 documented rabies cases reported in the United States in 2006, 2,615 (37.7%) were in raccoons.[164] The U.S. Department of Agriculture, as well as local authorities in several U.S. states and Canadian provinces, has developed oral vaccination programs to fight the spread of the disease in endangered populations.[165][166][167] Only one human fatality has been reported after transmission of the rabies virus from a raccoon.[168] Among the main symptoms for rabies in raccoons are a generally sickly appearance, impaired mobility, abnormal vocalization, and aggressiveness.[169] There may be no visible signs at all, however, and most individuals do not show the aggressive behavior seen in infected canids; rabid raccoons will often retire to their dens instead.[41][149][169] Organizations like the U.S. Forest Service encourage people to stay away from animals with unusual behavior or appearance, and to notify the proper authorities, such as an animal control officer from the local health department.[170][171] Since healthy animals, especially nursing mothers, will occasionally forage during the day, daylight activity is not a reliable indicator of illness in raccoons.[82]

Unlike rabies and at least a dozen other pathogens carried by raccoons, distemper, an epizootic virus, does not affect humans.[172] This disease is the most frequent natural cause of death in the North American raccoon population and affects individuals of all age groups.[122] For example, 94 of 145 raccoons died during an outbreak in Clifton, Ohio, in 1968.[173] It may occur along with a following inflammation of the brain (encephalitis), causing the animal to display rabies-like symptoms.[163] In Germany, the first eight cases of distemper were reported in 2007.[122]

Some of the most important bacterial diseases which affect raccoons are leptospirosis, listeriosis, tetanus, and tularemia. Although internal parasites weaken their immune systems, well-fed individuals can carry a great many roundworms in their digestive tracts without showing symptoms.[174] The larvae of the Baylisascaris procyonis roundworm, which can be contained in the feces and seldom causes a severe illness in humans, can be ingested when cleaning raccoon latrines without wearing breathing protection.[175]
Raccoons and people
Conflicts
A skunk and a raccoon share cat food morsels in a Hollywood, California, back yard
Standing on its rear paws, expecting a human to throw food crumbs in San Francisco, California

The increasing number of raccoons in urban areas has resulted in diverse reactions in humans, ranging from outrage at their presence to deliberate feeding.[176] Some wildlife experts and most public authorities caution against feeding wild animals because they might become increasingly obtrusive and dependent on humans as a food source.[177] Other experts challenge such arguments and give advice on feeding raccoons and other wildlife in their books.[178][179] Raccoons without a fear of humans are a concern to those who attribute this trait to rabies, but scientists point out this behavior is much more likely to be a behavioral adjustment to living in habitats with regular contact to humans for many generations.[180] Serious attacks on humans by groups of non-rabid raccoons are extremely rare and are almost always the result of the raccoon feeling threatened; at least one such attack has been documented.[181] Raccoons usually do not prey on domestic cats and dogs, but individual cases of killings have been reported.[182]

While overturned waste containers and raided fruit trees are just a nuisance to homeowners, it can cost several thousand dollars to repair damage caused by the use of attic space as dens.[183] Relocating or killing raccoons without a permit is forbidden in many urban areas on grounds of animal welfare. These methods usually only solve problems with particularly wild or aggressive individuals, since adequate dens are either known to several raccoons or will quickly be rediscovered.[171][184] Loud noises, flashing lights and unpleasant odors have proven particularly effective in driving away a mother and her kits before they would normally leave the nesting place (when the kits are about eight weeks old).[171][185] Typically, though, only precautionary measures to restrict access to food waste and den sites are effective in the long term.[171][186]

Among all fruits and crops cultivated in agricultural areas, sweet corn in its milk stage is particularly popular among raccoons.[187] In a two-year study by Purdue University researchers, published in 2004, raccoons were responsible for 87% of the damage to corn plants.[188] Like other predators, raccoons searching for food can break into poultry houses to feed on chickens, ducks, their eggs, or feed.[171][189] Since they may enter tents and try to open locked containers on camping grounds, campers are advised to not keep food or toothpaste inside a tent.[190]

Since raccoons in high mortality areas have a higher rate of reproduction, extensive hunting may not solve problems with raccoon populations. Older males also claim larger home ranges than younger ones, resulting in a lower population density. The costs of large-scale measures to eradicate raccoons from a given area are usually many times higher than the costs of the damage done by the raccoons.[41]
Mythology, arts, and entertainment
Stylized raccoon skin as depicted on the Raccoon Priests Gorget found at Spiro Mounds
See also: List of fictional raccoons

In the mythology of the indigenous peoples of the Americas, the raccoon was the subject of folk tales.[191] Stories such as "How raccoons catch so many crayfish" from the Tuscarora centered on its skills at foraging.[192] In other tales, the raccoon played the role of the trickster which outsmarts other animals, like coyotes and wolves.[193] Among others, the Dakota Sioux believed the raccoon had natural spirit powers, since its mask resembled the facial paintings, two-fingered swashes of black and white, used during rituals to connect to spirit beings.[194] The Aztecs linked supernatural abilities especially to females, whose commitment to their young was associated with the role of wise women in the tribal society.[195]

The raccoon also appears in Native American art across a wide geographic range. Petroglyphs with engraved raccoon tracks were found in Lewis Canyon, Texas; at the Crow Hollow petroglyph site in Grayson County, Kentucky;[196][197] and in river drainages near Tularosa, New Mexico and San Francisco, California.[198] A true-to-detail figurine made of quartz, the Ohio Mound Builders' Stone Pipe, was found near the Scioto River. The meaning and significance of the Raccoon Priests Gorget, which features a stylized carving of a raccoon and was found at the Spiro Mounds, Oklahoma, remains unknown.[199][200]

In Western culture, several autobiographical novels about living with a raccoon have been written, mostly for children. The best-known is Sterling North's Rascal, which recounts how he raised a kit during World War I. In recent years, anthropomorphic raccoons played main roles in the animated television series The Raccoons, the computer-animated film Over the Hedge and the video game series Sly Cooper.
Hunting and fur trade
Automobile coat made out of raccoon fur (1906, U.S.)

The fur of raccoons is used for clothing, especially for coats and coonskin caps. At present, it is the material used for the inaccurately named "sealskin" cap worn by the Royal Fusiliers of Great Britain.[201] Historically, Native American tribes not only used the fur for winter clothing, but also used the tails for ornament.[202] Since the late 18th century, various types of scent hounds which are able to tree animals ("coonhounds") have been bred in the United States.[203] In the 19th century, when coonskins occasionally even served as means of payment, several thousand raccoons were killed each year in the United States.[204] This number rose quickly when automobile coats became popular after the turn of the 20th century. In the 1920s, wearing a raccoon coat was regarded as status symbol among college students.[205] Attempts to breed raccoons in fur farms in the 1920s and 1930s in North America and Europe turned out not to be profitable, and farming was abandoned after prices for long-haired pelts dropped in the 1940s.[206][207] Although raccoons had become rare in the 1930s, at least 388,000 were killed during the hunting season of 1934/35.[208]
Coonskin cap

After persistent population increases began in the 1940s, the seasonal hunt reached about one million animals in 1946/47 and two million in 1962/63.[209] The 1948 senatorial campaign of Estes Kefauver, who wore such a cap for promotional purposes,[210] and the broadcast of three television episodes about the frontiersman Davy Crockett and the film Davy Crockett, King of the Wild Frontier in 1954 and 1955 led to a high demand for coonskin caps in the United States (though the caps supplied to the fad were typically made of faux fur with a raccoon tail attached).[211] Ironically, it is unlikely either Crockett or the actor who played him, Fess Parker, actually wore a cap made from raccoon fur.[212] The seasonal hunt reached an all-time high with 5.2 million animals in 1976/77 and ranged between 3.2 and 4.7 million for most of the 1980s. In 1982, the average pelt price was $20.[213] In the first half of the 1990s, the seasonal hunt dropped to 0.9 to 1.9 million due to decreasing pelt prices.[214] As of 1987, the raccoon was identified as the most important wild furbearer in North America in terms of revenue.[215]

In many parts of the United States, raccoon hunting is still done at night with dogs, usually breeds of coonhounds. The dogs track the raccoon until it seeks refuge, usually in a tree, where it is either harvested or left for future hunts. Hunters can tell the progress of tracking by the type of bark emitted by the dogs; a unique bark indicates the raccoon has been "treed".
As food

While primarily hunted for their fur, raccoons were also a source of food for Native Americans and Americans[216] and barbecued raccoon was a traditional food on American farms.[217] It was often a festive meal. Raccoon was eaten by American slaves at Christmas,[218] but it was not necessarily a dish of the poor or rural; in San Francisco's The Golden Era of December 21, 1856, raccoon is among the specialties advertised for the holiday, and US President Calvin Coolidge's pet raccoon Rebecca was originally sent to be served at the White House Thanksgiving Dinner.[219][220] The first edition of The Joy of Cooking, released in 1931, contained a recipe for preparing raccoon.

Because raccoons are generally thought of as endearing, cute, and/or varmints, the idea of eating them is repulsive to mainstream consumers.[221][222] However, many thousands of raccoons are still eaten each year in the United States.[223][224] Although the Delafield (Wisconsin) Coon Feed has been an annual event since 1928, its culinary use is mainly identified with certain regions of the American South like Arkansas where the Gillett Coon Supper is an important political event.[225][226]
As pets
Pen with climbing facilities, hiding places and a watering hole (on the lower left side)

As with most exotic pets, owning a raccoon often takes a significant amount of time and patience.[227] Raccoons may act unpredictably and aggressively and it can be quite difficult to teach them to obey and understand commands.[228] In places where keeping raccoons as pets is not forbidden, such as in Wisconsin and other U.S. states, an exotic pet permit may be required.[229][230]

Sexually mature raccoons often show aggressive natural behaviors such as biting during the mating season.[231] Neutering them at around five or six months of age decreases the chances of aggressive behavior developing.[232] Raccoons can become obese and suffer from other disorders due to poor diet and lack of exercise.[233] When fed with cat food over a long time period, raccoons can develop gout.[234] With respect to the research results regarding their social behavior, it is now required by law in Austria and Germany to keep at least two individuals to prevent loneliness.[235][236] Raccoons are usually kept in a pen (indoor or outdoor), also a legal requirement in Austria and Germany, rather than in the apartment where their natural curiosity may result in damage to property.[235][236][237]

When orphaned, it is possible for kits to be rehabilitated and reintroduced to the wild. However, it is uncertain whether they readapt well to life in the wild.[238] Feeding unweaned kits with cow's milk rather than a kitten replacement milk or a similar product can be dangerous to their health.[239]
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Old July 22nd, 2012 #5
Crowe
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Quote:
Originally Posted by Steven L. Akins View Post
Here's a coon with a pet coon:

(The older of the two coons was an old slave that belonged to my great-great-great-uncle, John T. Akins)



136 years old? So much for nigger slaves being mistreated.
 
Old July 22nd, 2012 #6
Roy Wagahuski
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Quote:
Originally Posted by Crowe
I have seen domesticated coons (4 legged variety), pot bellied pigs, as well as possums and coyotes. Find them when they are babies, and raise them up. Its possible to domesticate pretty much any Mammal, even many that would normally prey on humans in the wild.
They clearly distinguish 'domestication' apart from simply conditioning a still wild animal, that of the genes/instinct as opposed to the individual/memory, respectively.

But you didn't read the article and posted anyway.
 
Old July 22nd, 2012 #7
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Is there any sort of proof positive that all domesticated canines are descended from the wolf?

That never made much sense to me solely in terms of appearance.

Most, if not all, of the small to mid-sized breeds look to be far more closely related to the fox or coyote than to wolves.
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Old July 22nd, 2012 #8
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Originally Posted by MikeTodd View Post
Is there any sort of proof positive that all domesticated canines are descended from the wolf?

That never made much sense to me solely in terms of appearance.

Most, if not all, of the small to mid-sized breeds look to be far more closely related to the fox or coyote than to wolves.
Can a fox and a coyote be mated and produce a hybrid offspring the way that a donkey and a horse can be mated and produce a mule?
 
Old July 22nd, 2012 #9
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Originally Posted by Steven L. Akins
Can a fox and a coyote be mated and produce a hybrid offspring the way that a donkey and a horse can be mated and produce a mule?
Mongrelizers of all kinds should be beat with truncheons until broken, then thrown to wolves.
 
Old July 24th, 2012 #10
George Witzgall
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Originally Posted by Roy Wagahuski View Post
They clearly distinguish 'domestication' apart from simply conditioning a still wild animal, that of the genes/instinct as opposed to the individual/memory, respectively.

But you didn't read the article and posted anyway.
Fucking with the genes kills the fox. It isn't right; they turn into something else entirely.

Foxes are meant to be wild fellers. Doesn't mean if you live out in the country you can't enjoy them from a distance, or put out food for them. But if you get too close you smother them, kill them with greedy love. Even those you raised as cubs, you still have to respect their distance, and always remember they are wild at heart, and could one day take off and never look back.
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Old July 24th, 2012 #11
M.N. Dalvez
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Fucking with the genes kills the fox. It isn't right; they turn into something else entirely.
That's the point: from selectively breeding for traits you as the human find useful and/or desirable, over a number of generations, you end up with a different creature to the one you started out with.

You could say that cats are supposed to be wild fellers. Or wolves. But over a long time, we've made our cats and wolves into something quite different to what they were originally.

They still retain a lot of what they were, but they are comfortable with socialisation and can be trained to perform tasks.
 
Old July 25th, 2012 #12
Justin
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Originally Posted by Steven L. Akins View Post
Can a fox and a coyote be mated and produce a hybrid offspring the way that a donkey and a horse can be mated and produce a mule?
I'd imagine if it were possible it wouldn't be sterile like a mule. Such as how a dog/wolf hybrid isn't sterile. Those crazy racists, always poking holes in "anti-racism" with science... lol.
 
Old December 15th, 2012 #13
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Originally Posted by Steven L. Akins View Post
Can a fox and a coyote be mated and produce a hybrid offspring the way that a donkey and a horse can be mated and produce a mule?
All I have read, says NO! (A side point: Occasionally they do get a fertile mule. It is very rare. I've read this.) There have been instances of populations of wolves naturally mating with coyotes and eventually becoming coyotes. Thus, that wolf population disappears.

I've read that turkeys, pheasants, and pea fowl can produce offspring with chickens, and I knew a farmer who was agitated because rooster pheasant was getting into his hens, and his chicks were soon flying over fences and roaming freely.

I do believe that there are so many differences between African DNA and European DNA that we are different species, but that is no ground shaking revelation in here, of course.
 
Old December 15th, 2012 #14
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I do believe that there are so many differences between African DNA and European DNA that we are different species, but that is no ground shaking revelation in here, of course.

Pssst , don't tell anyone , but many biologists are now saying that a change in skin color is the hallmark of individuals in a species turning into a new species .

Imagine that , skin color having a major role in species development. Will wonders never cease ?

You don't suppose that nature would do this , so that individuals in the new higher species could select others of the same skill color so they didn't breed down , back to the lower species ?

Thomas Hunt Morgan* used skin color as the marker for the largest number genetic attributes of any marker .

Geez, but we all know that skin color doesn't matter , zog tells us so .


*( Nobel Prize in Medicine in 1933 for discoveries relating the role the chromosome plays in heredity)

Last edited by Itz_molecular; December 15th, 2012 at 10:16 PM.
 
Old December 22nd, 2012 #15
Crowe
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Many species of animals are classified as a different species by mostly appearance. A Polar bear and Grizzly bear are probably genetically close enough to interbreed, that doesn't make them the same.
 
Old December 22nd, 2012 #16
cillian
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Originally Posted by Steven L. Akins View Post
Here's a coon with a pet coon:

(The older of the two coons was an old slave that belonged to my great-great-great-uncle, John T. Akins)



Don't think I've ever seen a racoon in real life.

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Visual perception
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See also: Visual system

Visual perception is the ability to interpret the surrounding environment by processing information that is contained in visible light. The resulting perception is also known as eyesight, sight, or vision (adjectival form: visual, optical, or ocular). The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in psychology, cognitive science, neuroscience, and molecular biology.
Contents

1 Visual system
2 Study of visual perception
2.1 Early studies
2.2 Unconscious inference
2.3 Gestalt theory
2.4 Analysis of eye movement
2.5 Face and Object Recognition
3 The cognitive and computational approaches
4 Transduction
5 Opponent Process
6 Artificial visual perception
7 See also
7.1 Disorders/dysfunctions
7.2 Related disciplines
8 References
9 External links

Visual system
Main article: Visual system

The visual system in humans and animals allows individuals to assimilate information from the environment. The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive membrane in the back of the eye, called the retina. The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of patterns of light into neuronal signals. The lens of the eye focuses light on the photoreceptive cells of the retina, which detect the photons of light and respond by producing neural impulses. These signals are processed in a hierarchical fashion by different parts of the brain, from the retina upstream to central ganglia in the brain.

Note that up until now much of the above paragraph could apply to octopi, molluscs, worms, insects and things more primitive; anything with a more concentrated nervous system and better eyes than say a jellyfish. However, the following applies to mammals generally and birds (in modified form): The retina in these more complex animals sends fibers (the optic nerve) to the lateral geniculate nucleus, to the primary and secondary visual cortex of the brain. Signals from the retina can also travel directly from the retina to the superior colliculus.
Study of visual perception

The major problem in visual perception is that what people see is not simply a translation of retinal stimuli (i.e., the image on the retina). Thus people interested in perception have long struggled to explain what visual processing does to create what is actually seen.
Early studies
The visual dorsal stream (green) and ventral stream (purple) are shown. Much of the human cerebral cortex is involved in vision.

There were two major ancient Greek schools, providing a primitive explanation of how vision is carried out in the body.

The first was the "emission theory" which maintained that vision occurs when rays emanate from the eyes and are intercepted by visual objects. If an object was seen directly it was by 'means of rays' coming out of the eyes and again falling on the object. A refracted image was, however, seen by 'means of rays' as well, which came out of the eyes, traversed through the air, and after refraction, fell on the visible object which was sighted as the result of the movement of the rays from the eye. This theory was championed by scholars like Euclid and Ptolemy and their followers.

The second school advocated the so-called 'intro-mission' approach which sees vision as coming from something entering the eyes representative of the object. With its main propagators Aristotle, Galen and their followers, this theory seems to have some contact with modern theories of what vision really is, but it remained only a speculation lacking any experimental foundation.

Both schools of thought relied upon the principle that "like is only known by like", and thus upon the notion that the eye was composed of some "internal fire" which interacted with the "external fire" of visible light and made vision possible. Plato makes this assertion in his dialogue Timaeus, as does Aristotle, in his De Sensu.[1]
Leonardo DaVinci: The eye has a central line and everything that reaches the eye through this central line can be seen distinctly.

Alhazen (965 – c. 1040) carried out many investigations and experiments on visual perception, extended the work of Ptolemy on binocular vision, and commented on the anatomical works of Galen.[2][3]

Leonardo DaVinci (1452–1519) was the first to recognize the special optical qualities of the eye. He wrote "The function of the human eye ... was described by a large number of authors in a certain way. But I found it to be completely different." His main experimental finding was that there is only a distinct and clear vision at the line of sight, the optical line that ends at the fovea. Although he did not use these words literally he actually is the father of the modern distinction between foveal and peripheral vision.[citation needed]
Unconscious inference

Hermann von Helmholtz is often credited with the first study of visual perception in modern times. Helmholtz examined the human eye and concluded that it was, optically, rather poor. The poor-quality information gathered via the eye seemed to him to make vision impossible. He therefore concluded that vision could only be the result of some form of unconscious inferences: a matter of making assumptions and conclusions from incomplete data, based on previous experiences.

Inference requires prior experience of the world.

Examples of well-known assumptions, based on visual experience, are:

light comes from above
objects are normally not viewed from below
faces are seen (and recognized) upright.[4]
closer objects can block the view of more distant objects, but not vice versa

The study of visual illusions (cases when the inference process goes wrong) has yielded much insight into what sort of assumptions the visual system makes.

Another type of the unconscious inference hypothesis (based on probabilities) has recently been revived in so-called Bayesian studies of visual perception.[5] Proponents of this approach consider that the visual system performs some form of Bayesian inference to derive a perception from sensory data. Models based on this idea have been used to describe various visual subsystems, such as the perception of motion or the perception of depth.[6][7] The "wholly empirical theory of perception" is a related and newer approach that rationalizes visual perception without explicitly invoking Bayesian formalisms.[8]
Gestalt theory
Main article: Gestalt psychology

Gestalt psychologists working primarily in the 1930s and 1940s raised many of the research questions that are studied by vision scientists today.

The Gestalt Laws of Organization have guided the study of how people perceive visual components as organized patterns or wholes, instead of many different parts. Gestalt is a German word that partially translates to "configuration or pattern" along with "whole or emergent structure." According to this theory, there are six main factors that determine how the visual system automatically groups elements into patterns: Proximity, Similarity, Closure, Symmetry, Common Fate (i.e. common motion), and Continuity.
Analysis of eye movement
Eye movement first 2 seconds (Yarbus, 1967)

During the 1960s, technical development permitted the continuous registration of eye movement during reading[9] in picture viewing[10] and later in visual problem solving[11] and when headset-cameras became available, also during driving.[12]

The picture to the left shows what may happen during the first two seconds of visual inspection. While the background is out of focus, representing the peripheral vision, the first eye movement goes to the boots of the man (just because they are very near the starting fixation and have a reasonable contrast).

The following fixations jump from face to face. They might even permit comparisons between faces.

It may be concluded that the icon face is a very attractive search icon within the peripheral field of vision. The foveal vision adds detailed information to the peripheral first impression.

It can also be noted that there are three different types of eye movements: vergence movements, saccadic movements and pursuit movements. Vergence movements involve the cooperation of both eyes to allow for an image to fall on the same area of both retinas. This results in a single focused image. Saccadic movements is the type of eye movement that is used to rapidly scan a particular scene/image. Lastly, pursuit movement is used to follow objects in motion.[13]
Face and Object Recognition

There is some evidence (including disorders such as prosopagnosia) that face recognition is distinct from object recognition in terms of visual processing. For example, newborns show a preference for following moving faces within the first 30 minutes of life. However, some studies have shown that visual processing of complex non-face shapes happens in the same area of the brain as facial recognition. This implies it may be complexity, rather than the face per se, that influences visual processing in a distinct way.[14]
The cognitive and computational approaches

The major problem with the Gestalt laws (and the Gestalt school generally) is that they are descriptive not explanatory. For example, one cannot explain how humans see continuous contours by simply stating that the brain "prefers good continuity". Computational models of vision have had more success in explaining visual phenomena and have largely superseded Gestalt theory. More recently, the computational models of visual perception have been developed for Virtual Reality systems — these are closer to real life situation as they account for motion and activities which are prevalent in the real world.[15] Regarding Gestalt influence on the study of visual perception, Bruce, Green & Georgeson conclude:

"The physiological theory of the Gestaltists has fallen by the wayside, leaving us with a set of descriptive principles, but without a model of perceptual processing. Indeed, some of their "laws" of perceptual organisation today sound vague and inadequate. What is meant by a "good" or "simple" shape, for example?" [16]

In the 1970s David Marr developed a multi-level theory of vision, which analysed the process of vision at different levels of abstraction. In order to focus on the understanding of specific problems in vision, he identified three levels of analysis: the computational, algorithmic and implementational levels. Many vision scientists, including Tomaso Poggio, have embraced these levels of analysis and employed them to further characterize vision from a computational perspective.[citation needed]

The computational level addresses, at a high level of abstraction, the problems that the visual system must overcome. The algorithmic level attempts to identify the strategy that may be used to solve these problems. Finally, the implementational level attempts to explain how solutions to these problems are realized in neural circuitry.

Marr suggested that it is possible to investigate vision at any of these levels independently. Marr described vision as proceeding from a two-dimensional visual array (on the retina) to a three-dimensional description of the world as output. His stages of vision include:

a 2D or primal sketch of the scene, based on feature extraction of fundamental components of the scene, including edges, regions, etc. Note the similarity in concept to a pencil sketch drawn quickly by an artist as an impression.
a 2½ D sketch of the scene, where textures are acknowledged, etc. Note the similarity in concept to the stage in drawing where an artist highlights or shades areas of a scene, to provide depth.
a 3 D model, where the scene is visualized in a continuous, 3-dimensional map.[17]

Transduction
Main article: Visual phototransduction

Transduction is the process through which energy from environmental stimuli is converted to neural activity for the brain to understand and process. The back of the eye contains three different cell layers; Photoreceptor layer, Bipolar cell layer and Ganglion cell layer. The photoreceptor layer is at the very back and contains rod photoreceptors and cone photoreceptors. Cones are responsible for colour perception. There are three different cones: red, green and blue. Photoreceptors contain within them photopigments, composed of two molecules. There are 3 specific photopigments (each with their own colour) that respond to specific wavelengths of light. When the appropriate wavelength of light hits the photoreceptor, its photopigment splits into two, which sends a message to the bipolar cell layer, which in turn sends a message to the ganglion cells, which then send the information through the optic nerve to the brain. If the appropriate photopigment is not in the proper photoreceptor (for example, a green photopigment inside a red cone), a condition called colour blindness will occur.[18]
Opponent Process

Transduction involves chemical messages sent from the photoreceptors to the bipolar cells to the ganglion cells. Several photoreceptors may send their information to one ganglion cell. There are two types of ganglion cells: red / green and yellow/blue. These neuron cells consistently fire – even when not stimulated. The brain interprets different colours (and with a lot of information, an image) when the rate of firing of these neurons alters. Red light stimulates the red cone, which in turn stimulates the red/green ganglion cell. Likewise, green light stimulates the green cone, which stimulates the red/green ganglion cell and blue light stimulates the blue cone which stimulates the yellow/blue ganglion cell. The rate of firing of the ganglion cells is increased when it is signalled by one cone and decreased (inhibited) when it is signalled by the other cone. The first colour in the name if the ganglion cell is the colour that excites it and the second is the colour that inhibits it. I.e.: A red cone would excite the red/green ganglion cell and the green cone would inhibit the red/green ganglion cell. This is an opponent process. If the rate of firing of a red/green ganglion cell is increased, the brain would know that the light was red, if the rate was decreased, the brain would know that the colour of the light was green.[18]
Artificial visual perception

Theories and observations of visual perception have been the main source of inspiration for computer vision (also called machine vision, or computational vision). Special hardware structures and software algorithms provide machines with the capability to interpret the images coming from a camera or a sensor. Artificial Visual Perception has long been used in the industry and is now entering the domains of automotive and robotics.
See also

Naked eye
Color vision
Computer vision
Depth perception
Entoptic phenomenon
Lateral masking



Gestalt Psychology
Machine vision
Motion perception
Visual illusion
Visual processing

Disorders/dysfunctions

Achromatopsia
Akinetopsia
Apperceptive agnosia
Associative visual agnosia
Astigmatism



Color blindness
Prosopagnosia
Scotopic sensitivity syndrome
Recovery from blindness
Visual agnosia

Related disciplines

Cognitive science
Neuroscience
Optometry



Ophthalmology
Psychophysics

References

^ Finger, Stanley (1994). Origins of neuroscience: a history of explorations into brain function. Oxford [Oxfordshire]: Oxford University Press. ISBN 0-19-506503-4. OCLC 27151391.
^ Howard, I (1996). "Alhazen's neglected discoveries of visual phenomena". Perception 25 (10): 1203–1217. doi:10.1068/p251203. PMID 9027923.
^ Omar Khaleefa (1999). "Who Is the Founder of Psychophysics and Experimental Psychology?". American Journal of Islamic Social Sciences 16 (2).
^ Hans-Werner Hunziker, (2006) Im Auge des Lesers: foveale und periphere Wahrnehmung - vom Buchstabieren zur Lesefreude [In the eye of the reader: foveal and peripheral perception - from letter recognition to the joy of reading] Transmedia Stäubli Verlag Zürich 2006 ISBN 978-3-7266-0068-6
^ Stone JV, "Footprints Sticking Out of the Sand (Part II): Children’s Bayesian Priors For Lighting Direction and Convexity", Perception, 40(2), pp175-190, 2011.
^ Mamassian, Landy & Maloney (2002)
^ A Primer on Probabilistic Approaches to Visual Perception
^ The Wholly Empirical Theory of Perception
^ Taylor, Stanford E. (1965). "Eye Movements in Reading: Facts and Fallacies". American Educational Research Journal 2 (4): 187. doi:10.2307/1161646. ISSN 00028312.
^ Yarbus, A. L. (1967). Eye movements and vision, Plenum Press, New York
^ Hunziker, H. W. (1970). Visuelle Informationsaufnahme und Intelligenz: Eine Untersuchung über die Augenfixationen beim Problemlösen. Schweizerische Zeitschrift für Psychologie und ihre Anwendungen, 1970, 29, Nr 1/2
^ Cohen, A. S. (1983). Informationsaufnahme beim Befahren von Kurven, Psychologie für die Praxis 2/83, Bulletin der Schweizerischen Stiftung für Angewandte Psychologie
^ Carlson, Neil R. (2010). Psychology the Science of Behaviour. Toronto Ontario: Pearson Canada Inc.. pp. 140–141.
^ Alex Huk. (1999) "Object and Face Recognition: Lecture Notes." pp. 5
^ A.K.Beeharee - http://www.cs.ucl.ac.uk/staff/A.Beeharee/research.htm
^ Bruce, V., Green, P. & Georgeson, M. (1996). Visual perception: Physiology, psychology and ecology (3rd ed.). LEA. pp. 110.
^ Marr, D (1982). Vision: A Computational Investigation into the Human Representation and Processing of Visual Information. MIT Press.
^ a b Carlson, Neil R.; Heth, C. Donald (2010). "5". Psychology the science of behaviour (2nd ed.). Upper Saddle River, New Jersey, USA: Pearson Education Inc.. pp. 138–145. ISBN 978-0-205-64524-4.

External links
Wikiquote has a collection of quotations related to: Vision

Visual Perception 3 - Cultural and Environmental Factors
Gestalt Laws
Summary of Kosslyn et al.'s theory of high-level vision
The Organization of the Retina and Visual System
Reference info on aritificial visual perception
Dr Trippy's Sensorium A website dedicated to the study of the human sensorium and organisational behaviour
Effect of Detail on Visual Perception by Jon McLoone, the Wolfram Demonstrations Project.
The Joy of Visual Perception An excellent resource on the eye's perception abilities.
VisionScience. An Internet Resource for Research in Human and Animal Vision A most comprehensive collection of resources in vision science and perception.
Vision and Psychophysics. A quality account of many aspects of vision. However, some parts are missing.
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Neuroscience
Visual perception
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Perception
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Old December 22nd, 2012 #17
Steven L. Akins
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Quote:
Originally Posted by cillian View Post
Don't think I've ever seen a racoon in real life.
The only time I've ever seen them around here was pulling into my driveway at night. I see dead ones that have been hit by cars lying on the sides of roads all the time; but you never see a live one in broad daylight.

Foxes I've see in both daylight and at night. I once saw one walking across a parking lot inn front of store just before dusk. One of my neighbors had a mother fox give birth to a den of cubs under their house once. I've remember seeing a photo of a red-headed Scottish lass who had a pet fox in a National Geographic magazine from years ago, so evidently they can be tamed like raccoons, squirrels and other animals.
 
Old December 24th, 2012 #18
Roy
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I heard that an ape and a human have been successfully bred together. No, I don't mean black people with Whites, but the kind you see in a zoo. I haven't bothered to look for the literature (which I heard is Russian), but perhaps someone that can cite the scientific study can do so. If this has been scientifically proven, and not just a rumor, the current thinking of what is human and not would take on an entirely different meaning.
 
Old December 26th, 2012 #19
Bev
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There is a pair of semi=tame foxes, sometimes with cubs, who live on and around the farm near me. I often leave them leftover chicken, etc and have no doubt if I made it a regular occurrence rather than a sporadic one, they would become totally tame. They already hang around on the garden when they're hoping they may be something for them - the vixen screams to get attention (or used to - not heard much from her since my pup got to the guarding stage). I've already had to have a go at the local 'tard who decided to try and get them to come to him by moving a bowl of cat food closer and closer to his patio doors.

I would love them to be tame but sadly, there are too many morons around here who would abuse the trust so I take great care to keep them a little bit wary of me. Besides which, if they were fully dependent on me and others for food, the rat population caused by living near a farm/canal and by the council only collecting rubbish once in a blue moon would spiral out of control.
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Old December 26th, 2012 #20
Angel Ramsey
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Quote:
Originally Posted by Steven L. Akins View Post
The only time I've ever seen them around here was pulling into my driveway at night. I see dead ones that have been hit by cars lying on the sides of roads all the time; but you never see a live one in broad daylight.

Foxes I've see in both daylight and at night. I once saw one walking across a parking lot inn front of store just before dusk. One of my neighbors had a mother fox give birth to a den of cubs under their house once. I've remember seeing a photo of a red-headed Scottish lass who had a pet fox in a National Geographic magazine from years ago, so evidently they can be tamed like raccoons, squirrels and other animals.
I've seen two in the daylight. One my husband put it down. Probably rabid. The other a sheriff put down, right in the middle of the street.

We had 3 get into the garage a few months back. Mama, daddy, and baby. He put those 3 down as well. Too dangerous to our children and the outside cats.
 
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