Gemini Foxes: The Kit Fox and Swift Fox

Santa Cruz Island fox

In the first installment of Foxes of North America we introduced you to the beautiful and intelligent red fox, a fox that prefers to live on the edge and is very different from the island fox.

Here we'll take a quick look at the kit and swift foxes. Don't be fooled by their general appearance–they are not island foxes.

According to J. David Henry in his book Foxes: Living on the Edge, "The kit fox and the swift fox are the Gemini foxes of North America," because they share many physiological and morphological similarities. Kit and swift foxes inhabit the arid regions of North America and are adapted to habitats with relatively open vegetation.

 

Kit Fox, photo courtesy of CA Fish & Wildlife

Kit Fox

Kit foxes are native to the desert and semi-arid shrublands and grasslands of the southwestern US, including parts of Oregon, Colorado, and northwestern Mexico. They are a small fox species with a slender appearance, 5 pounds on average. Their coat is grizzled to tawny gray with buffy highlights on the neck, sides and legs. Their face has a typical "foxy" appearance, except for their ears, which are much longer than those of any other North American canid. This adaptation may help them dissipate body heat in the desert and could help them hunt insects and mice. To protect their feet from the hot sands, kit foxes have considerable hair between the pads, forming a kind of "sand shoe." Kit foxes are often confused with gray foxes because their ranges overlap, but kit foxes can be distinguished by the lack of a black ridge running the length of the tail as well as by their large ears.

The scientific name is Vulpes macrotis, which translates to "big eared fox."

San Joaquin Kit Fox, photo courtesy Tory Westall, ESRP - CSU Stanislaus

Kit foxes are opportunistic foragers that rely heavily on rodents and insects for sustenance. Kangaroo rats, pocket mice, and ground squirrels are common rodent prey. Like island foxes, kit foxes also consume beetles and grasshoppers. Kit foxes are also known to consume rabbits, birds, reptiles, and a variety of non-insect invertebrates

A unique feature of both the kit fox and the swift fox is the continuous use of underground dens throughout the year. Other canid species, including the island fox, use underground dens only during pup season. The Gemini Foxes clump their dens in suitable habitat and use them to provide critical protection from predators and shelter from extreme temperatures in desert summers and northern winters.

The San Joaquin subspecies of kit fox (V. macrotis mutica), which is restricted to the San Joaquin Valley and adjacent valleys in California, is currently listed as endangered under the Endangered Species Act. The kit fox is also listed as endangered by the State of Colorado and as threatened by the State of Oregon. The most serious threats include habitat loss and declining habitat suitability due to invasion of non-native grasses.

Swift Fox, photo courtesy K. Schafer

Swift Fox

Swift foxes primarily occur in the short and mixed-grass prairies from New Mexico and Texas north to southern Canada. Similar in size and appearance to the kit fox, the swift fox is pale yellowish-red and grey, with a thick grey stripe down its back that extends to its black-tipped tail. Its underside is lighter in color, and it has black patches on either side of its muzzle. You can distinguish swift foxes from kit foxes by the swift fox's smaller and rounder ears. Also, the swift fox's tail is shorter in relation to its body size than that of the kit fox.

Their scientific name is Vulpes velox, which simply translates to "swift fox."

 

Swift Fox, photo courtesy Gordon Court

 

Swift foxes are resourceful foragers, with a varied diet that includes small mammals, such as prairie dogs, birds, insects, plants and carrion. To reduce risk of predation by coyotes, swift foxes avoid areas with high prey density, such as areas of high plant diversity. They prefer open habitat where visibility is greatest.

Once abundant throughout their range, swift fox populations began to decline in the late 1800s due to rodent and predator control programs and the plowing of prairie into cultivated crop fields. As a result, the species is currently recognized as a species of conservation concern over much of its range. In Canada, the swift fox was gone or extripated by the 1930s. However, in 1983, a privately run program began breeding swift foxes in captivity in the US so that they could eventually be reintroduced back into the wild in Canada. Experts from this captive breeding effort provided advice for the captive breeding of island foxes in the early 2000s. While swift foxes are still classified as endangered, the swift fox's return is one of the most successful species reintroduction stories in Canada, just as the island fox's recovery is hailed as a success in the US.

Coming up next is the Fox of the Tundra: Arctic Fox

Series installments:

How is the Island Fox Unique?

Red Fox: Life on the Edge

Arctic Fox: Fox of the Tundra

The Island Fox's Origin - The Gray Fox

For additional information on the San Joaquin Kit fox visit: https://www.facebook.com/groups/friendsofthesjkf

References:

Butler, Andrew R., Kristy L.S. Bly, Heather Harris, Robert M. Inman, Axel Moehrenschlager, Donelle Schwaim, and David S. Jachowski. May 22, 2020. "Home range size and resource us by swift foxes in northeastern Montana." Journal of Mammalogy, vol. 101, (3), pg 684–696. Accessed at: https://doi.org/10.1093/jmammal/gyaa030

Cyper, B.L. 2003. "Foxes (Vulpes species, Urocyon species and Alopex lagopus)." In Wild Mammals of North America: Biology, Management, and Conservation, 2nd edition by G. Feldhamer, B. Thompson, and J. Chapman (eds), pg 511–546. Baltimore: Johns Hopkins University Press.

Elbroch, M. and K. Rinehart. 2001. Behavior of North American Mammals. pg 94–100. Peterson Reference Guides.

Harris, Heather (ed). July 2020. Swift Fox Conservation Team Report for 2017–2018. Montana: Montana Fish, Wildlife & Parks Glasgow.

Henry, J. D. 1996. Living on the Edge, Foxes. Minocqua, WI: Northword Press. 

Kelly, Erica C., Brian L. Cypher, and David J. Gemano. 2019. "Temporal variation in foraging patterns of Desert Kit Foxes (Vulpes macrotis arsipus) in the Mojave Desert, California, USA." Journal of Arid Environments, vol 167, pg 1–7. ISSN 0140-1963.

Meaney, C.A., M. Reed-Eckert, and G.P. Beauvais. August 21, 2006. Kit Fox (Vulpes macrotis): a technical conservation assessment. USDA Forest Service, Rocky Mountain Region. Accessed at: http://www.fs.fed.us/r2/projects/scp/assessments/kitfox.pdf 

 

 

Not All Foxes Are The Same - Red Fox vs. Island Fox

Santa Cruz Island fox

Foxes are small- to medium-sized members of the dog family that are found throughout the world. In North America there are six species of fox: Red Fox, Gray Fox, Kit Fox, Swift Fox, Arctic Fox, and of course, the Island Fox. Foxes are the smallest of the North American wild canids, the others being wolves and coyotes. Foxes are very intelligent and adaptable. They occupy varying landscapes across the continent from the vast Arctic tundra to the desert scrub land of the American southwest. From the wind-swept prairies to the boreal forests, the foxes of North America have carved out a niche as specially adapted predators of small prey. 

In the first of a multi-part post on different foxes, we'll introduce you to the Red Fox.

 

European red fox

 

Life on the Edge: Red Fox

The red fox is the most widely distributed land carnivore on the planet, with a range covering more than 28 million square miles. By contrast, the San Miguel Island fox has a very small range: only 24 square miles. Red foxes occupy five of the seven continents, including Australia, where they were introduced by English settlers in the 1800's. Only South America and Antarctica are free from these adaptable animals.

The scientific name for the red fox is Vulpes vulpes, the "fox's fox," which is fitting since most people conjure up an image of the red fox when asked about foxes. (Island fox's scientific name.) The presence of red foxes all over the world has led to their appearance in pop culture and folklore as people are readily drawn to this beautiful and cunning creature. More than any other canid, the red fox has received positive representation in literature and film. Aesop's Fables contain numerous tales of foxes. Disney's The Fox and the Hound tells the story of two unlikely friends, a red fox named Tod and a dog named Copper. To indigenous tribes of North America, the fox is a spiritual animal with different meanings across cultures–from a clever trickster to being associated with intelligence and wisdom.

Tod fox from Disney's The Fox and the Hound

 

Red foxes are the largest of the North American fox species, with a long, bushy tail, a narrow pointed muzzle, and thick soft fur. Their legs are slender with black fur covering the feet, nose, and the back of their erect, pointed ears. The coat of the upper body, head, and tail are bright red to yellowish-red. The tip of the tail is white. Adults are approximately 36–42 inches in total length and their tail accounts for slightly more than one-third of their length. Most adults weigh 10–11 pounds, as much as three times the size of an island fox.

Sacramento Valley red fox; photo courtesy Ben Sacks/UC Davis

Red foxes prefer habitat along edge environments where two habitat types meet, such as the intersection of open meadows and woodlands. In the west, red foxes are primarily found in higher, sub-alpine elevations. In California there are two native sub-species, the Sierra Nevada red fox and the newly described Sacramento Valley red fox. These two native red fox populations are small and geographically isolated (like being on an island). The study of island fox populations has played an important role in helping biologists evaluate the vulnerability of these red foxes to survive into the future.

Red foxes thrive near human settlements, most likely due to the protections humans provide against the foxes main predators: coyotes, bears, and mountain lions.

Red foxes are primarily active at twilight and night, although they may be seen during the day when foraging to feed their young. While omnivorous, their diet consists primarily of rodents, including voles, pocket gophers, and deer mice, as well as cottontail rabbits, jackrabbits, and snowshoe hairs. Like island foxes, red foxes readily eat fruits when they are in season. In some areas, fruits make up 100% of their diet! They commonly consume blueberries, blackberries, and raspberries, as well as apples, grapes, and even acorns.

Like many canids, North American foxes are basically monogamous, and the red fox is no different. Mating occurs between December and April. Pups are born between April and May. (Similar to island foxes.) The typical litter size is 3–6 pups. The male initially participates in feeding and rearing the kits, but moves on as the kits mature.

Red foxes are an adaptable and successful species. They have been extensively studied and their populations are stable apart from the two California sub-species. These beautiful animals extrude the cuddle factor more than any other fox species. (Well, except maybe island foxes.)

San Clemente Island fox

How is the Island Fox Unique?

Coming up next: Gemini Foxes: Kit Fox and Swift Fox;

Series installments:

How is the Island Fox Unique?

Gemini Foxes: Kit Fox and Swift Fox

Arctic Fox: Fox of the Tundra

The Island Fox's Origin - The Gray Fox

 

References:

Cyper, B.L. 2003. "Foxes (Vulpes species, Urocyon species and Alopex lagopus)." In Wild Mammals of North America: Biology, Management, and Conservation, 2nd edition by G. Feldhamer, B. Thompson, and J. Chapman (eds), pg 511–546. Baltimore: Johns Hopkins University Press.

Elbroch, M. and K. Rinehart. 2001. Behavior of North American Mammals. pg 105–111. Peterson Reference Guides.

Henry, J. D. 1996. Living on the Edge, Foxes. Minocqua, WI: Northword Press.

Saunders, D. A. 1988. "Red Fox: (Vulpes vulpes desmarest)." In Adirondack Mammals, pg 216. New York: State University of New York, College of Environmental Science and Forestry.

 

Unique As An Island Fox

We talk about the island fox being a unique and rare species, but what do we mean?

Unlike most North American fox species, the island fox (Urocyon littoralis) lives in very small, isolated habitats. Because each subspecies of island fox is limited to its specific island, all are restricted by geography to small populations. The smaller islands–San Miguel and San Nicolas–can only support a maximum of 400–500 individual island foxes. The largest two islands–Santa Cruz and Santa Catalina–appear able to sustain 2,000–2,500 individuals. Even at their maximum, these are small vulnerable populations. Current status

Island foxes are descended from one of the most, if not the most, ancient of living fox species, the gray fox (Urocyon cinereoargenteus). (island fox beside gray fox). As such, island foxes maintain some ancient traits that are shared with felines and other carnivore species, but not with other more modern canines–like wolves and red foxes.

Island foxes can rotate their front paws to climb. It is not unusual to see them up in small trees or large shrubs.

During captive breeding efforts to save island foxes from extinction, it was discovered that females do not go into a seasonal breeding heat. Female island foxes only have a hormonal surge and ovulate after contact with a male. This is called induced ovulation. Island foxes are the only known canine species to exhibit this reproductive trait, which is typical of cat and bear species. It is a primitive trait of Order Carnivora. This trait is most likely true for gray foxes, but because they are numerous in the wild, their reproduction has not been closely studied.

While the island fox evolved from an ancient canine lineage, it is a recently evolved species. Mitochondrial DNA places the island fox splitting away from the gray fox ancestor approximately 9,000 years ago.

Island foxes are the smallest fox species in North America. (island fox vs. fennec) Their small size is the result of island dwarfism. They also are impacted by island syndrome: changes in behavior and characteristics that have evolved over time due to the conditions in their island environment.

Island foxes are more active during the day than most gray foxes, because they lack a natural predator on the islands.

Resources on the Channel Islands are limited. Therefore, island foxes are highly omnivorous and eat a range of native fruits.

Living in a limited area, they sometimes experience higher density than most other fox species (more individuals living per square kilometer). Island foxes can be more accepting of other foxes in their territory during some parts of the year, but display higher levels of aggression and territoriality toward other foxes during breeding season. Observing island fox behavior

Island foxes have shortened tails. The number of vertebra in the tail ranges from 15–22 (depending on the subspecies). The cause or benefit for this adaptation remains unknown.

Perhaps the most unique trait of island foxes is their long and close relationship with humans. Living on the Channel Islands for thousands of years with indigenous peoples and then generations of ranchers, island foxes are habituated to people. They are wild creatures that are comfortable in the company of people. It is an amazing experience to share trails on the island with these bold little foxes. Step aside and they walk right past you.

 

In the following weeks we'll compare California's other fox species with the island fox.  

Series installments:

Red Fox: Life on the Edge

Gemini Foxes: Kit Fox and Swift Fox

Arctic Fox: Fox of the Tundra

The Island Fox's Origin - The Gray Fox

References

Coonan, Timothy J., Catherin A. Schwemm, and David K. Garcelon. 2010. Decline and Recovery of the Island Fox. Cambridge, UK: Cambridge University Press

Wang, Xiaoming and Richard H. Tedford. 2008. Dogs: Their Fossil Relatives & Evolutionary History. New York: Columbia University Press