Diving into the natural history of this taxon, the lineage leading toinitially diverged from other canids during the Miocene, which was 8-12 million years (MY) ago. Research has found that fossil , or gray foxes that have gone extinct, has been present in North America since the early Pliocene (~5 MY). Contemporary , or gray foxes that are currently extant, is the only extant canid with a natural range spanning both North and South America. Contemporary gray foxes have been classified into 15 subspecies based on morphology, in addition to six subspecies of island fox.
Currently, U. cinereoargenteus is listed as a “Least Concern” species in IUCN, while U. littoralis is listed as “Near Threatened” mainly due to infectious diseases. Conservation efforts and further research have been conducted, as well as constructing methods to mitigate disease in island foxes. (Coonan, et al., 2013; Goddard, et al., 2015; "Gray Foxes (Genus Urocyon)", 2021; Sanchez and Hudgens, 2020; Wilson and Reeder, 2007)
U. littoralis consists of the six Channel Islands off the coast of southern California. In the Northern Channel Island complex, they are found on San Miguel, Santa Rosa, and Santa Cruz Islands. In the Southern Channel Islands, they occur on San Nicolas, Santa Catalina, and San Clemente Islands.can be found from southern Canada to southern United States as a native in the Nearctic region, along with its native range also extending through northern Colombia and Venezuela in the Neotropical region. It is, however, not found in some mountainous parts of the Northwest United States and in the Great Plains. More specifically for island foxes, as their name implies, the range of
is considered as habitat generalists, but has a preference for selecting habitats containing forest cover, such as hardwood forests, mixed pine-hardwood forests, mature pine forests, mid-rotation pine plantations, and even residential areas and agriculture close to human dwellings. Of all canids, gray foxes are thought to be the most closely associated with hardwood forests, and many studies have also documented the common preference of mixed pine/hardwood forests by gray foxes. Studies have found that gray foxes are tolerant of urban and suburban landscapes, but use of suburban landscapes may also be limited by factors such as interactions with larger carnivores. For island foxes on the Channel Islands, they can also be found in valley and foothill grasslands, island chaparral, and coastal marshes.
During the Miocene, which occurred 8-12 MY ago, the lineage leading to U. cinereoargenteus has been found at almost 40 Pleistocene localities, the oldest of which date back to the late Irvingtonian or possibly the early Irvingtonian. These records also have found that U. littoralis evidently reached the Channel Islands off California in the late Pleistocene. The genus is considered to be the most basal of the living canids.initially diverged from other canids. The genus has been present in North America since the Hemphillian land mammal age (Pliocene; ~5 MY). Contemporary remains as the only extant canid with a natural range through North and South America. Fossil records show that
The naming of the genus U. littoralis was originally named Vulpes littoralis in 1857, with other common names for the island fox that include coast fox, short-tailed fox, island gray fox, channel island fox, channel islands gray fox, California channel island fox, and insular gray fox.can be attributed to the author Baird in 1857. This genus has no names that it was previously known as. However, the gray fox species
Two recent revisions of the family Canidae have suggested that Vulpes by Clutton-Brock et al. in 1976. However, genetic analyses of the fox-like canids confirmed that is a distinct genus from the red foxes (Vulpes). Genetically, often clusters with two other ancient lineages: the east Asian raccoon dog (Nyctereutes procyonoides) and the African bat-eared fox (Otocyon megalotis). Recent mitochondrial genetic studies suggest divergence of North American eastern and western gray foxes in the Irvingtonian, mid-Pleistocene into separate sister taxa.should be included as a subgenus of
Gray foxes share many diagnostic characteristics with other North American foxes, such as red foxes (Vulpes vulpes) and fennecs (Vulpes zerda). However, gray foxes have different characteristics and behaviors compared to some of their fox relatives that can easily distinguish them from the others. (Fritzell and Haroldson, 1982; Geffen, et al., 1992; Goddard, et al., 2015; Liu, 2002; Wilson and Reeder, 2007)
U. littoralis is a dwarf version of U. cinereoargenteus, with adults weighing between 1 to 3 kg, along with smaller body lengths between 590 to 790 mm. In both species, males tend to be slightly larger than females, but individuals of both sexes fall into the same length and weight ranges.is characterized with a grizzled appearance on the back and sides due to individual guard hairs that are banded with white, gray, and black. Typically, gray foxes have a total body length of 800 to 1125 mm, with a tail that is between 275 to 443 mm long. They also typically have a hindfoot length between 100 to 150 mm. Adult weights range from about 3 to 7 kg. It is to note that
Both extant species ofare considered as primarily monogamous. Adult gray foxes are socially monogamous and form pair-bonds, which contribute to the spatial behavior of each pair member. Pair formation and courtship generally occur from January through March, with most breeding occurring in late February and early March. During mating season, competition increases due to the need to attract mates, especially for males that display more aggression while defending mates. For example, they will sometimes give off a series of sharp barks or yips to attract their mate. Another method that gray foxes use to attract mates is the presence of scent glands on their face, pads of their feet, and inside their anus. These glands are primarily used to demarcate territory, but they are also used to attract potential mates.
One study has reported on a single mated pair that was found together 13.5% of the time. Another study radio-tracked two mated pairs during parts of the breeding and denning seasons. They found that the males foraged separately from the females at night, and usually returned to the den at daylight. Compared to the females, the males did not make repeated trips to the den. When the young reached 3 months of age, they accompanied their mothers as they left the den, and by 4 months of age, they started to forage independently.
It was also observed in another study where mated gray foxes were closer than expected to each other within their home ranges. Interactions among members of a mated pair may differ at fine temporal scales. Because gray foxes are socially monogamous, spatial overlap is common between adults in a pair-bond and these pairs maintain exclusive territories. Researchers suggest that the overlap among non-paired individuals is likely due to the result of relatedness among overlapping individuals. Indirect observations of social organization of gray foxes suggest that family units, composed of an adult male, adult female, and possibly juveniles, maintain spatially or temporally separate home ranges. The mated pair will remain together until late fall, but then will generally be solitary during the winter. (Deuel, et al., 2017b; Fritzell and Haroldson, 1982; Moore and Collins, 1995; Schutz, et al., 2009; Vu, 2011)
The breeding season of U. littoralis specifically, litter size can also range from one to five, with usually an average of two or three.varies geographically, though generally breeding activity extends from late January to May. The number of offspring per breeding season is an average between three to four young per female, though for
The gestation period of gray foxes is unknown; however, it has been reported to be an average of 63 days for U. cinereoargenteus, and a range between 50 to 53 days for U. littoralis. Parturition usually occurs from the end of April through early May. There have been no direct observations of parturition for U. littoralis, but studies suggest that the young of island foxes are born blind and helpless. Pups are typically weaned for over three to four weeks, though weaning is usually complete at about 6 weeks. The parents (primarily the female) start bringing solid food to the young before they are completely weaned.
Studies have found that the young emerge from the den at about three to four weeks of age. When pups reach two months of age, they spend most of the day outside of the den, and then they begin to forage with their parents in mid- to late June, and will continue to remain with their parents throughout the summer. The parents disperse away from the natal home range in late September, but the pups will remain in their natal areas until at least December. Both males and females are sexually mature by 10 months of age, soon after dispersal. It has been reported that juvenile gray foxes have dispersed as far as 84 km from their natal area. (Elbroch and Allen, 2013; Fritzell and Haroldson, 1982; Moore and Collins, 1995; Vu, 2011)
Both male and female parents take care of the offspring in the two extant species of. During pre-fertilization in a mated pair, the male will prioritize hunting for resources, while the female will prioritize searching for a den. After birth, both the mother and father will protect their pups. During the pre-independence period, the father is typically providing most of the food scraps, as well as teaching pups hunting skills. At three to six weeks, the pups are weaned and ready to hunt on their own. Both parents hunt for food separately at this point, since the pups are learning to hunt independently. Pups leave their mother in the fall when they are about 10 months old, since they’re sexually mature and ready to disperse at that stage.
Although gray foxes lack significant sexual dimorphism, home range sizes of males are generally slightly larger than females. However, male and female home ranges are both smaller and movement rates are less during denning, suggesting some degree of male investment in rearing young. Home ranges tend to be largest during breeding season, when pup rearing responsibilities have diminished and resource abundance may be low. Additionally, home ranges are intermediate during pup-rearing season, and the smallest while denning when adult movements are restricted as a result for caring for young.
Studies have found that adult gray foxes have relatively low annual survival rates, and both sexes continue to independently rear pups following mate loss, with a lone male’s ability to rear pups being dependent on whether pups have been weaned. When the pups disperse from their natal range, lone adults may be motivated to seek out a new mate to pair with for the upcoming breeding season if their mate died between the time of whelping and pup dispersal. (Deuel, et al., 2017a; Fritzell and Haroldson, 1982; Moore and Collins, 1995; Vu, 2011)
U. littoralis being the largest endemic post-Pleistocene land mammal on the Channel Islands, island foxes have been facing a decreased lifespan in the wild. There is currently no definitive average of their lifespan. (Fritzell and Haroldson, 1982; Hofman, et al., 2015; Vu, 2011)has a typical lifespan (captive and wild) that ranges between 6 to 8 years. There has been a report of gray foxes living up to 10 years in the wild, and 12 years in captivity. However, due to
U. cinereoargenteus, this species of gray fox is primarily nocturnal and crepuscular, with studies reporting that they travel greater distances per hour at night than during the day. However, local shifts in diurnal resting places are common as well. Usually, this species hunts at night and spends the day sleeping in hollow logs or underground burrows.mainly live a solitary, motile lifestyle. For
Compared to U. cinereoargenteus, U. littoralis has been observed to have more daytime activity, with peaks occurring during periods of low light intensity (e.g. sunset and sunrise). Radiotelemetry studies have reported that the activity patterns of island foxes vary seasonally in response to changes in ambient air temperature. For example, during the summer, island foxes show very little activity during the middle of the day, but they are most active during early mornings and evenings. On the other hand, during the winter, little activity occurs during early mornings and evenings, while most of the foraging occurs during the day.
A notable locomotion that gray foxes are known for are their agile, tree-climbing behavior (scansorial locomotion). Studies have observed gray foxes climbing vertical, branchless tree trunks with their semi-retractable claws. They are able to grasp the trunk with their forelimbs and then push up the trunk with their hindlimbs. Gray foxes have also been observed jumping from branch to branch, and descending down the trunk by either backing down the vertical tree or running headfirst down a sloping tree. Some of the reasons why they climb trees are because of foraging purposes, resting, or escaping from predators.
Based on radiotelemetry studies and relative trap success, the social organization of gray foxes have been observed to consist of family units, comprising an adult male and female, and possibly juveniles, in which they maintain spatially or temporally separate home ranges. However, one study observed a home range of four gray foxes, consisting of two males and two females, that occupied the same area during the spring and summer. (Fritzell and Haroldson, 1982; Liu, 2002; Moore and Collins, 1995; Vu, 2011)
U. littoralis barks have been compared to the barks of a rat terrier. Gray foxes also generally produce hisses and short, sharp growls during intraspecific aggression. All types of vocalizations are used by both sexes to establish dominance between individuals during intraspecific encounters.communicates with one another using visual, tactile, acoustic, and chemical signals. This includes the typical barking and growling communication behavior. They are commonly heard barking at night. A study has reported the principal sound frequencies of the bark of gray foxes. For example,
An observation of a social communication involves young gray foxes (5 to 8 weeks old) frequently raising a hind leg to show their genitalia to a conspecific, representing a submissive or appeasement gesture. Another study assessed that this leg-lifting behavior in juveniles seemed to be a mutual greeting, as paired pups were observed in mutual leg-lifting and smelling of each other’s genitalia after approaching one another. A third study observed a more aggressive-dominant behavior of the largest pup in the den presenting their genitalia to a runt, in which the dominant pup attacked the runt after the runt attempted to avoid it.
Juveniles also commonly play fight, where aggressive or playful attacks between gray foxes are directed at the cheek. Since the cheek is where the skin is especially thick, no critical damage is done during play fights. Intraspecific fighting is often accompanied by growling, barking, tail and ear biting, chasing, scuffling, and hip slamming.
Additionally, olfactory cues from urine and feces deposition play a role in intraspecific gray fox communication, along with how gray foxes perceive their environment. Evidence of this has been found in both extant species, where the deposition of urine and feces have been identified in conspicuous locations, such as on logs, rocks, small bushes, sticks, bare ground, and other elevated sites, as well as along trails and road edges. These scats are often deposited in groups. For adult gray foxes, marking of territories and food are done by using their scent glands. Furthermore, visual and acoustic cues are prevalent during foraging periods, especially hunting at night, as this allows gray foxes to be more alert for prey and be more successful with food captures. (Elbroch and Allen, 2013; Fritzell and Haroldson, 1982; Moore and Collins, 1995; Vu, 2011)
U. cinereoargenteus and U. littoralis have slightly different diets based on their resource availability due to their varied habitats.has an omnivorous diet, which consists of a variety of food depending on certain locations, seasons, and resource availability. This variety can include small vertebrates, fruit, seeds, and invertebrates. Both extant gray fox species
In multiple eastern and central states of the U.S., mammals are the predominant prey for U. cinereoargenteus, then followed by fruit and seeds, invertebrates, anthropogenic items, and birds. During the winter, lagomorphs (e.g. cottontail rabbits (Sylvilagus)), rodents (e.g. voles Microtus, deer mice Peromyscus, woodrats Neotoma, and cotton rats Sigmodon)) compose the largest portion of U. cinereoargenteus. During summer and autumn seasons, invertebrates (predominantly orthopterans, an order of insects which consists of grasshoppers, locusts, and crickets) mainly make up their diet. Additionally, plant foods like persimmon, berries, grapes, apples, and corn also increase in importance during the autumn, possibly forming up to 70% of the diet by volume. In one study, it was found that while analyzing gray fox scat compared to the coyote and bobcat scat, fruit consumption was at a high frequency during the summer and autumn, and almost all fruits eaten were manzanita berries. It was also found that when gray fox scats were largely composed of manzanita berries, their dietary breadth was narrower compared to coyotes and bobcats.
Less commonly eaten foods by U. cinereoargenteus are birds (including poultry), squirrels (Sciurus), opossum (Didelphis virginiana), and deer (Odocoileus) carrion. However, one study found that gray foxes were the principal predators of red-faced warbler (Cardellina rubrifrons) and yellow-eyed junco (Junco phaeonotus) nests within their study system, accounting for 89% of all nest depredations. Furthermore, another study observed gray foxes in the Chihuahuan Desert of northern Mexico and southwestern U.S. only scavenged on fresh, 1- or 2-day-old carrion.
The diet of U. littoralis is similar when compared to U. cinereoargenteus, but they primarily eat a wide variety of plants and animal remains. Island foxes are opportunistic foragers, in which they forage on any food items encountered within their home range, and they generally do not move great distances to feed on abundant, yet localized food resources. Varying according to seasonal availability of foods and the particular island sampled, island fox diet includes mice, ground nesting birds, arthropods, and fruits. The importance of fruit in the diet of island foxes is related to a plant's fruiting season. Island foxes have limited vertebrate prey due to the vertebrate fauna of the Channel Islands being depauperate. Compared to the gray fox, island foxes show a reduced dependence on vertebrate prey. Mammals, especially deer mice (Peromyscus maniculatus), comprise the largest vertebrate portion of the diets of island foxes on Santa Cruz Island, with deer mice comprising 53% of the volume of winter feces. Other potential rodent prey includes California ground squirrels (Spermophilus beecheyi), western harvest mice (Reithrodontomys megalotis), California voles (Microtus californicus), black rats (Rattus rattus), and house mice (Mus musculus). Reptiles and amphibians have reportedly not constituted a significant proportion of the overall diet of island foxes, though the Pacific chorus frog (Pseudacris regilla) is the only amphibian that island foxes are known to eat, and it has been suggested that island foxes may eat all species of reptiles that are found on the islands.
Human refuse areas and carrion (e.g. carcasses of pigs, sheep, cattle, and marine mammals), provide supplemental food sources for island foxes, especially when alternate foods are scarce. Like U. cinereoargenteus, insects (particularly orthopterans) are an important food source for island foxes. For example, the Jerusalem cricket (g.Stenopelmatus sp.) is the most important insect prey of island foxes. During summer and autumn seasons, grasshoppers have been predominantly found in the diets of island foxes. (Elbroch and Allen, 2013; Fritzell and Haroldson, 1982; Kirkpatrick and Conway, 2010; Larson, et al., 2015; Liu, 2002; Moore and Collins, 1995; Neale and Sacks, 2001; Vu, 2011)
The primary predators of Aquila chrysaetos), bobcats (Lynx rufus), coyotes (Canis latrans), and great horned owls (Bubo virginianus). Additional predators that more specifically prey on juvenile island foxes are red-tailed hawks (Buteo jamaicensis), domestic dogs (Canis domesticus), common ravens (Corvus corax) and bald eagles (Haliaeetus leucocephalus). However, humans are considered as the most significant predator of adult gray foxes due to being hunted for fur or killed by farmers that consider them as pests. For example, it has been reported that the total fur harvest of U. cinereoargenteus in the U.S. increased from about 26,000 individuals in 1970 to over 100,000 individuals in 1975, with a five-fold increase in average pelt price over the same period.are golden eagles (
Additionally, U. cinereoargenteus has been found as a host to many parasitic arthropods, such as fleas (Siphonaptera), lice (Phthiraptera), ticks (Ixodida), chiggers (Trombidiformes), and mites (Acari). A study found that unlike red foxes (Vulpes vulpes), gray foxes are highly resistant to infestation by sarcoptic mange mites (Sarcoptes scabiei). Gray foxes also host many species of internal parasites, such as trematodes (Trematoda), cestodes (Cestoda), nematodes (Nematoda), and acanthocephalans (Acanthocephala).
U. littoralis eat a wide variety of plant and animal remains, so they are considered as a keystone species within their habitat. Without island foxes, the natural ecosystem of the islands will most likely collapse. By preying on other island species, island foxes help keep their populations down. (Fritzell and Haroldson, 1982; Moore and Collins, 1995; Vu, 2011)
The fur pelts of Vulpes vulpes), gray foxes have shorter and coarser fur, thus making them less desirable in the market. More specifically for U. littoralis, Native Americans have used their fur for arrow quivers, capes, blankets, and head-dresses for ceremonial practices. In addition to being occasional hunting targets, gray foxes have been reportedly used for illegal pet trade purposes. (Fritzell and Haroldson, 1982; Hofman, et al., 2015; Liu, 2002; Moore and Collins, 1995; Vu, 2011)are collected and sold by humans via hunting and trapping, though compared to the pelts of red foxes (
In the genus U. cinereoargenteus currently has a stable population and listed as “Least Concern” in IUCN, while U. littoralis is currently listed as “Near Threatened” in IUCN, though there seems to be a slight increase trend in population size.,
Although the population size of the gray fox is stable, local populations are facing the threat of diseases, including rabies, canine distemper, tularemia, listeriosis, leptospirosis, histoplasmosis, toxoplasmosis, and Tyzzer’s disease. Another factor to consider is the hunting and trapping of gray foxes by humans during the regulated season. However, no special conservation efforts have been made to address this issue due to the large abundance of gray foxes currently.
The island fox is the largest endemic post-Pleistocene land mammal on the Channel Islands. Disease transmission and epidemic prevention have top priority in conservation efforts, especially for small, isolated populations like the island fox, which has a history of substantial population decline due to introduced disease. For example, island foxes are susceptible to ear mite infections. They have been currently treated with acaricides in an attempt to reduce mite infections and the morbidity and mortality associated with this highly prevalent tumor. A study found that it is critical to consider host densities at likely locations of pathogen invasion when designing disease management plans. (Coonan, et al., 2013; Cooper, et al., 2012; Fritzell and Haroldson, 1982; Hofman, et al., 2015; Moore and Collins, 1995; Sanchez and Hudgens, 2020; Vickers, et al., 2015)
Karen Yang (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
either directly causes, or indirectly transmits, a disease to a domestic animal
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
an animal that mainly eats fruit
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
An animal that eats mainly insects or spiders.
animals that live only on an island or set of islands.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).
parental care is carried out by males
eats mollusks, members of Phylum Mollusca
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
generally wanders from place to place, usually within a well-defined range.
an animal that mainly eats all kinds of things, including plants and animals
the business of buying and selling animals for people to keep in their homes as pets.
chemicals released into air or water that are detected by and responded to by other animals of the same species
an animal that mainly eats dead animals
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
places a food item in a special place to be eaten later. Also called "hoarding"
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
young are relatively well-developed when born
2021. "Gray Foxes (Genus Urocyon)" (On-line). iNaturalist. Accessed September 07, 2021 at https://www.inaturalist.org/taxa/42075-Urocyon.
Coonan, T., K. Ralls, B. Hudgens, B. Cypher, C. Boser. 2013. "Urocyon littoralis. The IUCN Red List of Threatened Species" (On-line). Accessed September 07, 2021 at https://dx.doi.org/10.2305/IUCN.UK.2013-2.RLTS.T22781A13985603.en.
Cooper, S., C. Nielsen, P. McDonald. 2012. Landscape factors affecting relative abundance of gray foxes Urocyon cinereoargenteus at large scales in Illinois, USA. Wildlife Biology, 18(4): 366-373.
Deuel, N., L. Conner, K. Miller, M. Chamberlain, M. Cherry, L. Tannenbaum. 2017. Gray fox home range, spatial overlap, mated pair interactions and extra-territorial forays in southwestern Georgia, USA. Wildlife Biology, 2: 1-10.
Deuel, N., L. Conner, K. Miller, M. Chamberlain, M. Cherry, L. Tannenbaum. 2017. Habitat selection and diurnal refugia of gray foxes in southwestern Georgia, USA. PLoS ONE, 12(10): 1-12.
Egan, M., C. Day, T. Katzner, P. Zollner. 2021. Relative abundance of coyotes (Canis latrans) influences gray fox (Urocyon cinereoargenteus) occupancy across the eastern United States. Canadian Journal of Zoology, 99(2): 63-72.
Elbroch, L., M. Allen. 2013. Prey Indices and Behaviors at a Gray Fox Den in San Mateo County, California. Western North American Naturalist, 73(2): 240-243.
Fritzell, E., K. Haroldson. 1982. Urocyon cinereoargenteus. Mammalian Species, 189: 1-8.
Geffen, E., A. Mercure, D. Girman, D. MacDonald, R. Wayne. 1992. Phylogenetic relationships of the fox-like canids: mitochondrial DNA restriction fragment, site and cytochrome b sequence analyses. Journal of Zoology, 228: 27-39.
Goddard, N., M. Statham, B. Sacks. 2015. Mitochondrial Analysis of the Most Basal Canid Reveals Deep Divergence between Eastern and Western North American Gray Foxes (Urocyon spp.) and Ancient Roots in Pleistocene California. PLoS ONE, 10(8): 1-21.
Gompper, M., A. Petrites, R. Lyman. 2006. Cozumel Island fox (Urocyon sp.) dwarfism and possible divergence history based on subfossil bones. Journal of Zoology, 270(1): 72-77.
Hofman, C., T. Rick, M. Hawkins, W. Funk, K. Ralls, C. Boser, P. Collins, T. Coonan, J. King, S. Morrison, S. Newsome, T. Sillett, R. Fleischer, J. Maldonado. 2015. Mitochondrial Genomes Suggest Rapid Evolution of Dwarf California Channel Islands Foxes (Urocyon littoralis). PLoS ONE, 10(2): 1-15.
Kapfer, J., R. Kirk. 2012. Observations of Gray Foxes (Urocyon cinereoargenteus) in a Suburban Landscape in the Piedmont of North Carolina. Southeastern Naturalist, 11(3): 507-516.
Kirkpatrick, C., C. Conway. 2010. Nest Predators of Ground-nesting Birds in Montane Forest of the Santa Catalina Mountains, Arizona. Wilson Journal of Ornithology, 122(3): 614-617.
Larson, R., D. Morin, I. Wierzbowska, K. Crooks. 2015. Food Habits of Coyotes, Gray Foxes, and Bobcats in a Coastal Southern California Urban Landscape. Western North American Naturalist, 75(3): 339-347.
Liu, S. 2002. "Urocyon littoralis" (On-line). Animal Diversity Web. Accessed September 14, 2021 at https://animaldiversity.org/accounts/Urocyon_littoralis/.
Moore, C., P. Collins. 1995. Urocyon littoralis. Mammalian Species, 489: 1-7.
Neale, J., B. Sacks. 2001. Food habits and space use of gray foxes in relation to sympatric coyotes and bobcats. Canadian Journal of Zoology, 79(10): 1794-1800.
Roemer, G., B. Cypher, R. List. 2016. "Urocyon cinereoargenteus. The IUCN Red List of Threatened Species" (On-line). Accessed September 07, 2021 at https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T22780A46178068.en.
Sanchez, J., B. Hudgens. 2020. Vaccination and monitoring strategies for epidemic prevention and detection in the Channel Island fox (Urocyon littoralis). PLoS ONE, 15(5): 1-22.
Schutz, H., P. Polly, J. Krieger, R. Guralnick. 2009. Differential sexual dimorphism: size and shape in the cranium and pelvis of grey foxes (Urocyon). Biological Journal of the Linnean Society, 96(2): 339-353.
Temple, D., M. Chamberlain, L. Conner. 2010. Spatial Ecology, Survival and Cause-Specific Mortality of Gray Foxes (Urocyon cinereoargenteus) in a Longleaf Pine Ecosystem. American Midland Naturalist, 163(2): 413-422.
Vickers, T., D. Clifford, D. Garcelon, J. King, C. Duncan, P. Gaffney, W. Boyce. 2015. Pathology and Epidemiology of Ceruminous Gland Tumors among Endangered Santa Catalina Island Foxes (Urocyon littoralis catalinae) in the Channel Islands, USA. PLoS ONE, 10(11): 1-18.
Vu, L. 2011. "Urocyon cinereoargenteus" (On-line). Animal Diversity Web. Accessed September 14, 2021 at https://animaldiversity.org/accounts/Urocyon_cinereoargenteus/.
Wilson, D., D. Reeder. 2007. "Urocyon" (On-line). Mammal Species of the World. A Taxonomic and Geographic Reference (3rd ed). Accessed September 14, 2021 at https://www.departments.bucknell.edu/biology/resources/msw3/browse.asp?s=y&id=14000840.