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Gray Fox - Urocyon cinereoargenteus
Gray Fox - Urocyon cinereoargenteus

[Image: Grey-fox-climbing-tree.jpg]

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Genus: Urocyon
Species: Urocyon cinereoargenteus (Schreber, 1775)

The gray fox (Urocyon cinereoargenteus), or grey fox, is a carnivorous mammal of the family Canidae, widespread throughout North and Central America. This species and its only congener, the diminutive Channel Island Fox (Urocyon littoralis), are the only living members of the genus Urocyon, which is considered to be the most basal of the living canids. Though it was once the most common fox in the eastern United States, and still is found there, human advancement and deforestation allowed the Red Fox to become more dominant. The Pacific States still have the gray fox as a dominant. It is the only American canid that can climb trees. Its specific epithet cinereoargenteus means "ashen silver".

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The gray fox is mainly distinguished from most other canids by its grizzled upper parts, black-tipped tail and strong neck, while the skull can be easily distinguished from all other North American canids by its widely separated temporal ridges that form a U-shape. There is little sexual dimorphism, save for the females being slightly smaller than males. The gray fox ranges from 76 to 112.5 cm (29.9 to 44.3 in) in total length. The tail measures 27.5 to 44.3 cm (10.8 to 17.4 in) of that length and its hind feet measure 100 to 150 mm (3.9 to 5.9 in). The gray fox typically weighs 3.6 to 7 kg (7.9 to 15.4 lb), though exceptionally can weigh as much as 9 kg (20 lb). It is readily differentiated from the Red Fox by the lack of "black stockings" that stand out on the latter and the stripe of black hair that runs along the middle of the tail as well as individual guard hairs being banded with white, gray, and black. The gray fox displays white on the ears, throat, chest, belly and hind legs. In contrast to all Vulpes and related (Arctic and Fennec) foxes, the gray fox has oval (instead of slit-like) pupils.

[Image: Grey-fox-yawning.jpg]

Origin and genetics
The gray fox appeared in North America during the mid-Pliocene (Hemphillian land animal age) epoch 3.6 million years ago (AEO) with the first fossil evidence found at the lower 111 Ranch site, Graham County, Arizona with contemporary mammals like the giant sloth, the elephant-like Cuvieronius, the large-headed llama, and the early small horses of Nannippus and Equus. Genetic analyses of the fox-like canids confirmed that the gray fox is a distinct genus from the Red Foxes (Vulpes spp.). Genetically, the gray fox often clusters with two other ancient lineages, the east Asian Raccoon Dog (Nyctereutes procyonoides) and the African Bat-eared Fox (Otocyon megalotis). The chromosome number is 66 (diploid) with a fundamental number of 70. The autosomes include 31 pairs of sub-graded subacrocentrics, but one only pair of metacentrics. Faunal remains at two northern California cave sites confirm the presence of the gray fox during the late Pleistocene. Genetic analysis has shown that the gray fox migrated into the northeastern United States post-Pleistocene in association with the Medieval Climate Anomaly warming trend. Recent mitochondrial genetic studies suggests divergence of North American eastern and western gray foxes in the Irvingtonian mid-Pleistocene into separate sister taxa.

The gray fox's dwarf relative, the Channel Island Fox, is likely descended from mainland gray foxes. These foxes apparently were transported by humans to the islands and from island to island, and are descended from a minimum of 3–4 matrilineal founders. The genus Urocyon is considered to be the most basal of the living canids.

[Image: Grey-fox-in-rocky-habitat.jpg]

Distribution and habitat
The species occurs throughout most rocky, wooded, brushy regions of the southern half of North America from southern Canada to the northern part of South America (Venezuela and Colombia), excluding the mountains of northwestern United States. It is the only canid whose natural range spans both North and South America. In some areas, high population densities exist near brush-covered bluffs.

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The gray fox's ability to climb trees is shared only with the Asian Raccoon Dog among canids. Its strong, hooked claws allow it to scramble up trees to escape many predators, such as the domestic dog or the coyote, or to reach tree-bound or arboreal food sources. It can climb branchless, vertical trunks to heights of 18 meters and jump from branch to branch. It descends primarily by jumping from branch to branch, or by descending slowly backwards as a domestic cat would do. The gray fox is primarily nocturnal or crepuscular and makes its den in hollow trees, stumps or appropriated burrows during the day. Such gray fox tree dens may be located 30 ft above the ground. Prior to European colonization of North America, the Red Fox was found primarily in boreal forest and the gray fox in deciduous forest, but now the Red Fox is dominant in most of the eastern United States since they are the more adaptable species to development and urbanization. In areas where both red and gray foxes exist, the gray fox is dominant.

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The gray fox is assumed monogamous. The breeding season of the gray fox varies geographically; in Michigan, the gray fox mates in early March, in Alabama, breeding peaks occur in February. The gestation period lasts approximately 53 days. Litter size ranges from 1 to 7, with a mean of 3.8 young per female. The sexual maturity of females is around 10 months of age. Kits begin to hunt with their parents at the age of 3 months. By the time that they are four months old, the kits will have developed their permanent dentition and can now easily forage on their own. The family group remains together until the autumn, when the young males reach sexual maturity, then they disperse. Out of a study of nine juvenile gray foxes, only the males dispersed up to 84 km. The juvenile females stayed within proximity of the den within 3 km and always returned. On the other hand, adult gray foxes showed no signs of dispersion for either gender.

The annual reproductive cycle of males has been described through epididymal smears and become fertile earlier and remain fertile longer than the fertility of females.

Dens are used at any time during the year but mostly during whelping season. Dens are built in brushy or wooded regions and are less obvious than the dens of the Red Fox. Logs, trees, rocks, burrows, or abandoned dwellings serve as suitable den sites.

[Image: Grey-fox-in-snow-covered-woodland.jpg]

The gray fox is an omnivorous, solitary hunter. It frequently preys on the eastern cottontail (Sylvilagus floridanus) in the eastern U.S., though it will readily catch voles, shrews, and birds. In California, the gray fox primarily eats rodents, followed by lagomorphs, e.g. jackrabbit, brush rabbit, etc. In some parts of the Western United States (such as in the Zion National Park in Utah), the gray fox is primarily insectivorous and herbivorous. Fruit is an important component of the diet of the gray fox and they seek whatever fruits are readily available, generally eating more vegetable matter than does the Red Fox (Vulpes vulpes).

There are 16 subspecies recognized for the gray fox.
  • Urocyon cinereoargenteus borealis (New England)

  • Urocyon cinereoargenteus californicus (southern California)

  • Urocyon cinereoargenteus cinereoargenteus (eastern United States)

  • Urocyon cinereoargenteus costaricensis (Costa Rica)

  • Urocyon cinereoargenteus floridanus (Gulf states)

  • Urocyon cinereoargenteus fraterculus (Yucatán)

  • Urocyon cinereoargenteus furvus (Panama)

  • Urocyon cinereoargenteus guatemalae (southernmost Mexico south to Nicaragua)

  • Urocyon cinereoargenteus madrensis (southern Sonora, south-west Chihuahua, and north-west Durango)

  • Urocyon cinereoargenteus nigrirostris (south-west Mexico)

  • Urocyon cinereoargenteus ocythous (Central Plains states)

  • Urocyon cinereoargenteus orinomus (southern Mexico, Isthmus of Tehuantepec)

  • Urocyon cinereoargenteus peninsularis (Baja California)

  • Urocyon cinereoargenteus scottii (south-western United States and northern Mexico)

  • Urocyon cinereoargenteus townsendi (northern California and Oregon)

  • Urocyon cinereoargenteus venezuelae (Colombia and Venezuela)
Parasites of gray fox include trematode Metorchis conjunctus.

[Image: Grey-fox.jpg]
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Information related to Gray Foxes:

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Just a minor bit of information comparing fox aggression - 

"Gray foxes are often more aggressive than red fox and an abundance of gray fox will prevent an abundance of red fox in the same habitat. "

Canidae Wrote:BBC Wildlife Magazine's December issue had a lot of interesting info about Grey Foxes in the Sonoran Desert, Arizona - the scoop done by Alexander Badyaev.

The whole magazine / article is worth a thread with some great pictures but here are some interesting bits in particular :

They can be quite good and frequent hunters of birds :
"It pauses at the level of the injunction between cactus arm and trunk, about 10 cm up; for a moment it listens to the sound of the desert, then, in two quick leaps, delves into the cavity. A few seconds of struggle ensue before it emerges with the unfortunate, still-flapping tenant and hops back to the ironwood tree," - The bird was a Gilded Woodpecker

Of tree climbing :
"Like Primates, it has rotating wrists that enable it to grip the sides of trees the climb branchless tree trunks.
It hauls itself up branches with short, powerful forearms that would not be out of place on a miniture badger.
But when a Grey fox does slip, it invariably catches itself and regains its lofty position in a remarkably primate like fashion - clawing at the bark with widely spread digits and pulling itself up on a branch.

"in early summer, when cactus flowers and fruits are abundant, these delicacies make up most of the fox's diet. Then, during the 'monsoon' months of July to early September, when the Sonoran Desert becomes lush and green, its diet is augmented with plenty of migratory grasshoppers, crickets and large nocturnal moths
"the fox will terrorise high-roosting birds, chase cottontail rabbits and pull them from their burrows, search for and destroy bird nests, and trail herds of collared peccaries in the hope of stealing newborn piglets.
" (A picture of a fox with a treed piglet kill was featured.)

Of kill stashing and 'skeleton trees':
"To my suprise, infra-red video I filmed near one such 'skeleton' tree revealed it to be a social centre for a pair of local Grey Foxes that visit it nightly; they bring food, chase each other, nap, rearrange their macabre collection and generally make themselves at home. They are exceptionally strong, routinley dragging the remnants of coyote kills high into the canopy. These dried out bones seem to be used mostly for marking spots and resting as, effectivley, high-elevation fold-out beds." (A picture of a large ungulate spine, skull and ribs were shown in a tree with 2 foxes.)

Of coyotes :
"the foxes are frequentley killed by local Coyotes and, occaisionally, bobcats. A shocking 90% of all grey fox mortalities in this desert are the work of coyotes, which routinely ambush the foxes, pin them to the ground and dispatch them with bites to their necks.
Though each can cover more than 5km in one night, often trotting around in the dark for hours, a fox will rarely venture farther than a short spring awy from its favourite escape tree. When suitably large trees are available, a mother will prefer to whelp her cubs in a tree cavity.
" (A picture of a treed Fox with a Coyote beneath the tree was featured.)
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Foxes may confuse predators by rubbing themselves in puma scent

[Image: nationalgeographic_2329436.jpg]
A smelly solution?
Maresa Pryor/Lightwave Photography Inc./NGS Creative

By Richard Gray
DAILY NEWS 19 January 2017

They have a reputation as cunning creatures, and some foxes appear to be living up to it as masters of disguise.

Gray foxes living in the mountains of California have been filmed deliberately rubbing themselves in the scent marks left by mountain lions.

They may be using the scent of the big cats, also known as pumas or cougars, as a sort of odour camouflage against other large predators such as coyotes.

Coyotes often kill gray foxes, which are half their size, to reduce competition.

Max Allen, an ecologist at the University of Wisconsin at Madison, had been studying pumas visiting sites known as “community scrapes”, where males leave scent “signposts” to communicate with others.

Surprise visitors
He was surprised when remote cameras set up to monitor the mountain lions revealed foxes also regularly visiting these sites.

Analysis of footage taken over four years at 26 different sites revealed the foxes were rubbing their cheeks on bits of ground that had been freshly marked by the mountain lions, often within hours of a big cat’s visit.

“The foxes rub very specifically on the areas where the pumas mark,” says Allen. “Coyotes are very reliant upon smell when hunting and are much bigger than the foxes. The foxes have a hard time fighting back, so they use this to give themselves a chance to escape.”

Allen and his colleagues found 92 out of 903 documented visits by foxes involved cheek rubbing. And 85 per cent of the foxes that exhibited this behaviour did so on spots where pumas had deposited their scent. The team did not see any similar behaviour from coyotes or bobcats, which also visited the sites far less frequently than the foxes.

Many animals rub their cheeks and bodies on stones, trees and the ground to leave their scent behind. Allen’s video footage, however, showed the foxes rubbing themselves in the puma scrape five times more often than they did on shrubs or unmarked ground at those sites.

This suggests they were focused on applying puma scent onto themselves, rather than depositing their own scent.

Escape strategy

There are various reasons why foxes might do this. But Allen’s team says that predator avoidance seems the most likely hypothesis and is worth exploring further.

“Gray foxes climb trees to avoid predators,” says Allen. “In many cases, they probably only need a few seconds’ hesitation from a coyote for them to get up a tree. Smelling like a puma might give them that time.”

But there may be another explanation, says Steve Harris, an ecologist who studies foxes at the University of Bristol in the UK.

“Foxes use their saliva as scent and have glands in the region of the lips,” he says. “My impression is that the gray foxes are stimulated by the strong odours left by the pumas and are depositing their own scent.”

Allen and his colleagues hope to use tags on some gray foxes to study whether foxes that have rubbed themselves in puma scent are more likely to survive predation.

Journal reference: 
Allen, M.L., Gunther, M.S. & Wilmers, C.C. The scent of your enemy is my friend? The acquisition of large carnivore scent by a smaller carnivore J Ethol (2017) 35: 13. doi:10.1007/s10164-016-0492-6

Scent marking is critical to intraspecific communication in many mammal species, but little is known regarding its role in communication among different species. We used 4 years of motion-triggered video to document the use of scent marking areas—termed “community scrapes”—by pumas (Puma concolor) ( and other carnivore species. We found that gray foxes (Urocyon cinereoargenteus) routinely rubbed their cheeks on puma scrapes (, and tested a series of hypotheses to determine its function. We found that gray foxes selected puma scrapes over other objects, and cheek rubbing by foxes was also correlated with how recently a puma had visited the scrape, suggesting that foxes were intent upon accumulating fresh puma scent. Cheek rubbing by foxes was not correlated with their breeding season or with how recently another fox had visited the site. Finally we found a cascading pattern in the occurrence of pumas, coyotes (Canis latrans) and gray foxes at community scrapes, suggesting that gray foxes may use puma scent to deter predation. This is the first published study to find evidence of a subordinate species using the scent of a dominant species to communicate with heterospecifics. The behavioral cascade we found in scent marking patterns also suggests that scent marking could be a mechanism that impacts the distribution and abundance of species. Additional videos pertaining to this article include, and 
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Novel research approach sheds light on how midsize predators interact

Date: February 5, 2018
Source: Oregon State University

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The fisher is an important forest predator in the U.S. and Canada.
Credit: David Green, OSU Institute for Natural Resources

A novel research approach by Oregon State University has resulted in a key step toward better protecting the fisher, an important forest predator that findings show is the dominant small carnivore when present.

The study by OSU's Institute for Natural Resources focused on how three carnivores -- ringtails, foxes, and fishers -- affect each other's population numbers and colonization behavior. Findings were published today in the Journal of Animal Ecology.

Despite what their name suggests, fishers don't actually eat fish, but one thing the fierce and furry animal does do is force foxes to fend differently, the research shows.

Fishers are so named because early North American settlers noticed a resemblance to the European polecat, which was also called a fitch, fitchet or fitchew.

Native only to Canada and the northern United States, the long-tailed forest dwellers saw their numbers dwindle due to fur trapping and logging. Fishers are a member of the Mustelidae family that also includes wolverines, badgers, otters and minks.

"They're larger than people realize," said corresponding author David Green. "They can be the size of a large house cat, and they're really interesting critters."

Fishers climb trees like a cat but are able, thanks to hind feet that can rotate almost 180 degrees, to climb down headfirst. That trick helps them kill porcupines by attacking the quilled animal's non-quilled head from above.

Green and colleagues spent eight years studying fishers and other predators in a 179-square-mile region on the Oregon-California border.

Their main objective was to see how translocating fishers -- in this case moving them from the study area to reintroduce them to the northern Sierra Nevada mountains -- influenced their numbers; researchers also wanted to learn about the effects fishers and other predators of similar size have on each other.

"There's been quite a bit of research that shows how larger carnivores have negative effects on fishers, but this is some of first research to look at their interactions with carnivores of about their same size," said Green, whose group also included researchers from North Carolina State University, the U.S. Forest Service, the U.S. Fish and Wildlife Service and the California Department of Fish and Wildlife.

"Throughout the world, numbers of grey foxes, fishers and other midsized predators are actually increasing, and usually that happens because the bigger animals that are limiting them are decreasing. But we thought we might also see changes in midsized predator numbers because of some kind of hierarchy among them. The idea that they could be interacting with other carnivores their same size in ways that might affect their distribution was new, novel and important to pursue."

Green's team looked at the effects translocating nine fishers had on fisher populations and occupancy in the study region, and also on the translocation's effects on ringtails and grey foxes. The nine animals removed for reintroduction represented about 20 percent of the study area's fisher population.

"The foxes likely compete with fishers due to their similar sizes and dietary overlap," Green said. "And ringtails are similar to fishers in that both are semi-arboreal and of conservation concern. Determining how all of those types of animals coexist is critical for understanding functional diversity, niche partitioning and interspecific interactions."

Following the removal, the fishers' population density was unchanged, but they occupied fewer places -- certain home ranges would become vacant. Site occupancy by the foxes increased and remained elevated throughout the study.

"We sampled the animals using non-invasive means -- capturing hair as they visited our baited sampling sites -- and we used genetic techniques to identify the animals that visited our sites down to the individual fisher," Green said. "We found a complicated hierarchy among fishers, foxes and ringtails. In summary, fishers were the dominant small carnivore where present, and they negatively affected foxes directly and ringtails indirectly."

Green described the findings as encouraging as well as interesting.

"I think of this as a beginning step to understand how fishers interact with other species in their environment," Green said. "But the big picture right now is funding for research like this is declining rapidly given the current state of government agencies, and it's important for research like this to continue to move forward so we can better understand one of the important and charismatic species in the Northwest and the nation."

Story Source: Oregon State University. "Novel research approach sheds light on how midsize predators interact." ScienceDaily. (accessed February 5, 2018).

Journal Reference:
David S. Green, Sean M. Matthews, Robert C. Swiers, Richard L. Callas, J. Scott Yaeger, Stuart Farber, Michael K. Schwartz, Roger A. Powell. Dynamic occupancy modeling reveals a hierarchy of competition among fishers, gray foxes, and ringtails. Journal of Animal Ecology, 2017; DOI: 10.1111/1365-2656.12791

1.Determining how species coexist is critical for understanding functional diversity, niche partitioning and interspecific interactions. Identifying the direct and indirect interactions among sympatric carnivores that enable their coexistence are particularly important to elucidate because they are integral for maintaining ecosystem function. 
2.We studied the effects of removing 9 fishers (Pekania pennanti) on their population dynamics and used this perturbation to elucidate the interspecific interactions among fishers, gray foxes (Urocyon cinereoargenteus), and ringtails (Bassariscus astutus). Gray foxes (family: Canidae) are likely to compete with fishers due to their similar body sizes and dietary overlap, and ringtails (family: Procyonidae), like fishers, are semi-arboreal species of conservation concern. We used spatial capture-recapture to investigate fisher population numbers and dynamic occupancy models that incorporated interspecific interactions to investigate the effects members of these species had on the colonization and persistence of each other's site occupancy. 
3.The fisher population showed no change in density for up to three years following the removals of fishers for translocations. In contrast, fisher site occupancy decreased in the years immediately following the translocations. During this same time period, site occupancy by gray foxes increased and remained elevated through the end of the study. 
4.We found a complicated hierarchy among fishers, foxes, and ringtails. Fishers affected gray fox site persistence negatively but had a positive effect on their colonization. Foxes had a positive effect on ringtail site colonization. Thus, fishers were the dominant small carnivore where present and negatively affected foxes directly and ringtails indirectly. 
5.Coexistence among the small carnivores we studied appears to reflect dynamic spatial partitioning. Conservation and management efforts should investigate how intraguild interactions may influence the recolonization of carnivores to previously occupied landscapes.
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