Silver foxes exist in seasonally monogamous pairs for the breeding months of December to April, and most matings occur in January and February. Female silver foxes are monestrous (having 1 estrus cycle per year) with estrus lasting 1–6 days and parturition occurring after about 52 days of gestation. During or approaching estrus, the vulva of silver foxes increases in size and tumescence, indicating the sexual readiness or condition of the fox.
The result of over 50 years of experiments in the Soviet Union and Russia, the breeding project was set up in 1959 by Soviet scientist Dmitri Belyaev. It continues today at the Institute of Cytology and Genetics at Novosibirsk, under the supervision of Lyudmila Trut.
In the richness and beauty of its splendid fur the Silver-gray Fox surpasses the beaver or sea otter, and the skins are indeed so highly esteemed that the finest command extraordinary prices, and are always in demand.
Sadly for the fox, Australia and New Zealand have recently decided to remove this introduced species in an attempt to help reduce the loss of biodiversity, and there are now control measures in places, with bans on the release and re-homing of sick or injured foxes as a result.
"Leucism... is a condition in which there is partial loss of pigmentation in an animal resulting in white, pale, or patchy colouration of the skin, hair, feathers, scales or cuticle, but not the eyes... Unlike albinism, it is caused by a reduction in multiple types of pigment, not just melanin."
While foxes are primarily carnivores, they eat a wide variety of foods including, but not restricted to;
The silver fox morph is very behaviorally similar to the red morph. One common behavior is scent marking. This behavior is used as a display of dominance, but may also be used to communicate the absence of food from foraging areas as well as social records.
"For each of the genes investigated specific SNP profiles characteristic only for farm foxes and only for wild foxes were noted. At the same time, specific SNP profiles were noted for wild foxes from North America and from Europe."
The project also bred the least-tame foxes to study social behavior in canids. These foxes avoided human contact as do their wild behavioral phenotypes.
In the former Soviet Union, silver foxes occur mostly in forest zones and forest–tundra belts, particularly in middle and eastern Siberia and the Caucasus mountains. They are very rare in steppes and deserts.
The experiment was initiated by scientists who were interested in the topic of domestication and the process by which wolves became domesticated dogs. They saw some retention of juvenile traits by adult dogs, both morphological ones, such as skulls that were unusually broad for their length, and behavioral ones, such as whining, barking, and submission.
"Xanthochromism... is an unusually yellow pigmentation in an animal. It is often associated with the lack of usual red pigmentation and its replacement with yellow. The cause is usually genetic but may also be related to the animal's diet... The opposite of xanthochromism, a deficiency in or complete absence of yellow pigment, is known as axanthism."
A domestic silver fox is a canid developed via a genetics experiment originally funded by the Soviet Union. The program began in 1959 and utilized a silvery gray color variant of the wild red fox, Vulpes vulpes. The experiment succeeded in producing a strain of tame foxes.
Domestic silver foxes in the UK are descendants of domestic fur farm foxes (rather than those scientifically domesticated), which are now bred haphazardly by exotic pet breeders for tameness and suitability to live life as a pet, some with more success than others. Such animals originate from lines of farmed silver foxes that display a much greater variety of polymorphism than is seen in wild red foxes in the UK;
"Psysiological causes of coloration, including melanism, are evident but poorly researched. The relative importance of evolutionary forces responsible for external coloration varies greatly between vertebrate taxa, but the reasons for this variation are not yet understood"
Belyaev's and Trut's original interest in fox domestication was based in the belief that selection for behavior, such as tameness, mimicked past natural selection with ancestral dogs. This quality was thought to be the most significant indicator of how well adaptation would occur amongst dogs and humans.
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In addition, the silver fox has been represented in different forms of media. On television, in films, and in comic books, Silver Fox is a character in the Wolverine superhero series. In literature, the characters Scarface and Lady Blue from The Animals of Farthing Wood are silver foxes. Recently, it has evolved another meaning in our everyday speech. The term "silver fox" can refer to an older man or woman who is nonetheless still wise and charming.
Both farmed silver foxes and Russian domesticated foxes have a greater ability to cope with stress compared to wild foxes, making them bolder than their wild counterparts. There are further differences again between farmed silver foxes and those scientifically domesticated for tameness;
Silver foxes engage in a system of biparental care, which is associated with their seasonal monogamous mating scheme. For a given litter, males contribute a large investment in the offspring by both feeding and protecting the den. While the pups are early in development, the male secures food for the nursing vixen. Whereas males are more vigilant in defending the den, females also defend their offspring aggressively.
Belyaev and Trut believe that selecting for tameness mimics the natural selection that must have occurred in the ancestral past of dogs, and, more than any other quality, must have determined how well an animal would adapt to life among humans.
"Erythrism or erythrochroism refers to an unusual reddish pigmentation of an animal's fur, hair, skin, feathers, or eggshells... Causes of erythrism include genetic mutations which cause an absence of a normal pigment and/or excessive production of others..."
The Russian Domesticated Red Fox is a domesticated form of the red fox (Vulpes vulpes). As a result of selective breeding, the new foxes became tamer and more dog-like.
The selective breeding of melanistic foxes by man for the fur trade (since at least the late 1800's ), pre-dates our production of inbred laboratory strains of rodents (early 1900's) and this is reflected in EU litrature from 1999, that considers fur farm foxes "domesticated farm animals".
Foxes have long been branded as being cunning, mischievous, and manipulative characters in fables. But how would they fare if given characteristics such as friendly, happy, affectionate and loyal? Believe it or not these are some of the characteristics that arose from an experiment conducted by the late Dmitry Belyaev in Novosibirsk, Russia.
On average adult foxes are not much bigger than a house cat, around 30-60 cm in length and weighing between 3-11 kg.
Russian domesticated foxes exhibit a variety of coat colors, including red, silver (black), platinum, cross, and Georgian White, the lattermost being a color exclusive to the Russian breeding project.
"Research observations [on the differences between domesticated and non-domesticated foxes]."
In another study published in Behavior Genetics, a system of measuring fox behavior was described that is expected to be useful in QTL mapping to explore the genetic basis of tame and aggressive behavior in foxes.
Domestic Silver Fox
"Overall, silver foxes account for about 10% of colour morphs. Jet black foxes are, however, very rare in Europe; in his 2005 Carnivores of the World, Ronald Nowak notes that such foxes are confined to the extreme north of Europe and make up about 1% of the population"
In a time when centralized political control in the fields of genetics and agriculture promoted Lysenkoism as an official state doctrine, Belyaev's commitment to classical genetics had cost him his job as head of the Department of Fur Animal Breeding at the Central Research Laboratory of Fur Breeding in Moscow in 1948. During the 1950s, he continued to conduct genetic research under the guise of studying animal physiology.
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Hybrids between the American Red fox and the European Red fox are possible, as they are essentially the same species (foxes were once classified as "vulpes vulpes" in Eurasia and "vulpes fulvus" in the Americas (Tesky, 1995), but since 1959 they have been considered a singular species, of which there are ten subspecies - American red foxes being "vulpes vulpes fulvus" and Eurpoean red foxes being "vulpes vulpes crucigera").
Foxes have whiskers and scent glands on their face and legs that help them both communicate; by informing other foxes of sex, status and individual identity, and to navigate; by allowing them to judge distance and space.
Red foxes are extremely intelligent and adaptable animals, they are native to Europe and can be found throughout the the British Isles, being absent from some of the smaller islands due to their isolated location. They are also native to North America and North Africa. They have also been introduced to Australia, New Zealand and now China, as a form of pest control.
The domestication of the red fox has produced the silver fox, oftentimes referred to as the Siberian fox. This domestication is due to selective breeding, resulting in tamer and more dog-like foxes.
Similar research was carried out in Denmark with American mink.
A Russian Domesticated Red Fox with classic red fur color.
Statistically, 70% of wild foxes will not make it through their first year. Foxes that do make it through their first year live an average of 4-5 years, while their captive counterparts have been known to live up to 12 years and over.
Colour Morphs in US Foxes - Living With Foxes