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The Silver Fox (Vulpes vulpes) is a melanistic form of red fox. Silver foxes display a great deal of pelt variation: some are completely black except for a white coloration on the tip of the tail, some are bluish-grey, and some may have a cinereous colour on the sides. Historically, silver foxes were among the most valued furbearers, and their skins were frequently worn by nobles in Russia, Western Europe, and China. Wild silver foxes do not naturally reproduce exclusively with members of the same coat morph, and can be littermates with the common red variety, though captive populations bred for their fur are almost exclusively mated with members of the same colour.
The silver fox's long outer hair can extend as far as two inches (5 cm) beyond the shorter underfur on different parts of the fox's body, particularly under the throat, behind the shoulders, on the sides and the tail. The hair of the underfur is brown at the base, and silver grey tipped with black further along the follicle. The hair is soft, glossy and was once reputed to be finer than that of the pine marten. The uniformly blackish brown or chocolate coloured underfur, which is unusually long and dense, measures in some places two inches and is exceedingly fine. It surrounds the whole body even to the tail, where it is a little coarser and woollier. The fur is shortest on the forehead and limbs, and is finer on the fox's underbelly. When viewed individually, the hairs composing the belly fur exhibit a wavy appearance. There are scarcely any long hair on the ears, which are thickly clothed with fur. The soles of the feet are so thickly covered with woolly hair so that no callous spots are visible. According to East-Siberian hunters, the footprints of silver foxes are larger than those of the red variety, due to larger foot pads and greater amounts of fur in this area of the body. Silver foxes also tend to be more cautious than red foxes.
When bred with another member of the same colour morph, silver foxes will produce silver coated offspring, with little variation in this trend after the third generation. When mated to pure red foxes, the resulting cubs will be fiery red in overall coat color, and will have blacker markings on the belly, neck and points than average red foxes. When one such fiery red fox is mated with a silver one, the litter is almost always 50% silver and 50% red. Fiery red parents may occasionally produce a silver cub, the usual proportion being one in four. Occasionally, the colours of mixed foxes blend rather than segregate. The blended offspring of a silver and red fox is known as a cross fox.
Silver foxes are one of the most widely distributed carnivorous species in the world, ranging over much of the northern hemisphere and Australia. Their abundance in a wide variety of habitats can be attributed to introduction by humans into new habitats for fox-hunting.
In North America, silver foxes occur mostly in northwestern part of the continent. In the 19th century, silver foxes were sometimes taken in Labrador, the Magdalen Islands and rarely in the mountainous regions of Pennsylvania and the wilder portions of New York. They were occasionally found in Nova Scotia. According to Sir John Richardson, a greater number than 4-5 silver foxes were rarely taken in any one season in areas where they were present, though trappers would prioritise them above all other furbearers once they were discovered. Silver foxes comprise up to 8% of Canada's red fox population.
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.
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.—John James Audubon, quoted from The Imperial Collection of Audubon Animals, 1967
"[Silver Foxes] are glossy black on their necks, where no silver hairs are found. The black must be of a bluish cast all over the body rather than a reddish. The under fur must also be dark colored. The fur of silver and black foxes is a dark slate next to the skin. The silver hairs have pure silver bands, but they're not white nor very prominent. In the costliest skins there are only a few silver hairs, which are well scattered over the pelt. Flakiness, which is the appearance of whitish silver hairs placed close together in patches, is objectionable. Buyers pass judgement on the skins by drawing the hand over the fur. The softest fur is the most valuable. The quality of softness is referred to as 'silkiness.' The sheen must be evident. It is caused by the perfect health of the animal and the fineness of the hair, as well as by hereditary influences. Woods and humid atmosphere also favour this important quality. A good fox skin will weigh at least one pound, the weight usually varying from ten to nineteen ounces. The thick, long fur makes the weight. This is a very important point, as heavy fur is more durable and handsome. The value of silver fox pelts increases with the size."—The Fur Trade of America by Agnes C. Laut, 1921
The fur of a silver fox was once considered by the natives of New England to be worth over 40 American beaver skins. A chieftain accepting a gift of silver fox fur was seen as an act of reconciliation. The records of the Hudson's Bay Company indicate that 19–25% of fox skins traded in British Columbia in the years 1825–1850 were silver, as were 16% of those traded in Labrador. The fur was almost always sold to Russian and Chinese traders. Before the practice of fur farming was eventually refined on Prince Edward Island, it was standard practice to release free ranging silver foxes into small islands, where they quickly starved to death. Fur farmers on Prince Edward Island gained success by breeding and caring for their foxes in captivity. Also, Prince Edward Island fur farmers recognised the species' monogamous habits and permitted their studs to mate for life with a single female. The fur of captive bred foxes was of a better quality than that of free ranging ones (worth $500–1,000 rather than $20–30) because of better care and diet. These silver foxes would be bred strictly with members of their own colour morph, and by the third generation, all residual traces of red or cross ancestry disappeared.
Silver foxes in Russian fur farms are of North American stock, and are selectively bred in order to remove as much brown from the fur as possible, as the presence of brown fur lowers the pelt's value. Estonia began farming silver foxes in 1924, after receiving 2,500 foundation specimens from Norway to Mustajõe farm. The numbers of Estonian silver fox farms steadily increased in the following decades. During the Soviet period, the silver fox industry boomed due to government subsidies and a focus on selectively breeding foxes for greater fertility than fur quality.
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.
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.
Female silver foxes generally breed during their first autumn, but a number of factors that contribute to their breeding success. Age, food, population density, and mating system (polygyny or monogamy) all affect impregnation success rates and litter size. Higher population density leads to a higher incidence of failure in producing pups. Silver foxes have litters that typically range from 1 to 14 pups, with the average being 3 to 6 pups. Litter size generally increases with age an abundance of food.Scientists have observed an increase in reproductive success with age in silver fox morphs, which may be attributable to yearlings breeding an average of nine days after adults. Success in larger litters depends highly on the availability of extra-parental care via the assistance of unmated females. This is particularly notable in higher density populations, where some females fail to produce pups.
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.
In captivity, differential reproductive success can be attributed to variation in the competition capacity among individual females. Competition capacity is defined as the ability of individuals to dominate resources such as food or nesting sites. The competition capacity of the mother directly influences the fitness of her offspring. In one experiment where vixens, whose competition capacities were categorized as high, medium, or low, were bred under standard farming conditions, competition capacity was positively associated with the number of healthy offspring raised to weaning. This study has led to the use of competition capacity as a more encompassing measure of reproductive fitness for the silver fox. Some vixens have also been noted to engage in infanticide. These vixens generated more weaned cubs during their next reproductive cycle than those who did not engage in infanticide. This may suggest the conservation of efforts or investment to increase future reproductive success. Infanticidal vixens infrequently adopt and help to raise the young of neighboring vixens after eating their own.
While silver foxes are opportunistic feeders and will consume any food presented to them, they prefer a more carnivorous diet when meat is available. When meat is scarce, they rely more heavily on plant material. Like the red morph, the silver fox adapts different strategies when hunting different prey. When hunting smaller mammals, the foxes adapt a “mousing position” from which they can locate prey based on sound. Subsequently, the foxes launch themselves, pin prey to the ground using their forepaws, and kill it by biting. Quicker terrestrial prey requires more practiced behavior, often involving stalking and rapid pursuit. When prey escapes to hidden caches or burrows, foxes are known to occasionally nap beside the entrances and lie in wait for prey to reemerge.
The Silver Foxes have been involved in fairly extensive experiments of selection dating back to the Soviet era. The domestication of the silver fox morph by Russian scientists demonstrates the ability to select for levels of aggressiveness and certain behavioral characteristics. Perhaps the most astonishing occurrence in these selection experiments is the almost immediate physical manifestations of selection. The study itself has provided a viable hypothesis for how the fox's relative, the dog, came to be domesticated from wolves. As this relates to human interactions with the species, silver foxes were noted to be less stressed (lower plasma cortisol levels) when handled by humans early in development. In comparison, wild silver foxes or those not handled were more likely to experience higher stress levels and had higher plasma levels of cortisol.
The domesticated silver fox is the result of over 50 years of experiments in the Soviet Union and Russia to domesticate the silver fox. The breeding project was set up in the 1950s by the Soviet scientist Dmitri K. Belyaev. As a result of selective breeding, the new foxes not only have become tamer, but more dog-like as well. The domesticated foxes exhibit both behavioral and physiological changes from their wild forebears. They are friendlier with humans, put their ears down (like dogs), wag their tails when happy, and have begun to vocalize and bark like domesticated dogs. They have also developed color patterns like domesticated dogs and have lost their distinctive musky "fox smell."
According to the creation myth of the Achomawi people of California, the silver fox originated as a fog which formed at the creation of the earth, and subsequently became human. Travelling the water-covered earth in a canoe, the silver fox unintentionally created land masses by throwing the hair stuck to his comb into the sea.
Two silver foxes serve as supporters for the Coat of arms of Prince Edward Island. Traditionally, heraldic foxes symbolize sagacity, wit and wisdom. The silver foxes on the Coat of arms of Prince Edward Island further symbolize inspiration, ingenuity and perseverance, in light of Edward Island's refining of fur farming.
The characters Scarface and Lady Blue from The Animals of Farthing Wood are silver foxes.