Friday, April 09, 2021

Island Foxes On Facebook

Friends of the Island Fox is migrating!


OK, we're moving to a new Facebook home.

FIF has been on Facebook since April 2011. We've changed, Facebook has changed, and island foxes on Santa Rosa Island have gone from a population of 449 to an estimated 2,427.

We want to keep telling you about island fox conservation successes!

If you follow us on Facebook, we hope you'll migrate to: 

FIF's New Facebook page

 @FriendsoftheIslandFox

The old page will no longer be updated. 

We're expanding our horizons, just like this island fox spotted last week on a mountain top on Santa Rosa Island.


Spread the news to your friends.

You can also follow us on Twitter @ifoxtweet or sign-up for our bimonthly e-newsletter.

Friday, April 02, 2021

Fox Foto Friday - Island Foxes in Washington D.C.?

What smells like an island fox? Came from an island fox? But is contained on the tip of a cotton swab? A sample of island fox microbiome.

Island fox being swab with cotton swab

Friends of the Island Fox recently heard from FIF 2020 Research Grant recipient, Alexandria DeCandia, Ph.D.

DeCandia wrote "I wanted to let you know that microbiome samples from all six islands have arrived on the east coast :)" Swabs taken from island foxes during health checks have been transferred to a lab in Washington D.C. She added, "I'm very much looking forward to the next steps of this research!"


FIF's Research Grant is funding the DNA analysis of the swabs to get a picture of the biodiversity of microbes living on and in island foxes.

What Is She Looking For?

DeCandia's research is cutting edge science. Her early analysis of Catalina Island foxes led to some important findings on the possible relationships between bacteria in island fox ear canals and a tendency toward extreme immune system response to ear mites. This next stage of research builds on that work.

Maintaining healthy island foxes across the islands requires greater in depth understanding of their health, diet, position in the ecosystem, and interactions with other species, including humans. 

Friends of the Island Fox invests in research to invest in the island fox's future. Applications for the FIF 2021 Research Grant will be available April 15, 2021.

Friday, March 19, 2021

Is That An Island Fox? Identifying North American Foxes


Fox species overlap in many parts of North America, which can make it difficult to distinguish one species from the next. In California alone, there are four fox species:

The last three occur only on the mainland. If you are fortunate to see a small to medium canid in the field, you should ask yourself a few questions to aid in identification:

fox silhouette


 

coyote silhouette

1. Is it a coyote or a fox? 


Coyotes now inhabit most of North America, but they are typically larger than foxes and appear more dog-like with a larger face. The coyote tail is also shorter for their body than a fox's. While most foxes have distinct color markings to aid in identification, coyotes do not.


If it is a fox: 

2. Start with the tip of the tail:

White tail tip: Probably a red fox. Even if the fur coloring is not red or cinnamon, a fox with a white-tipped tail is a red fox.  The image to the right shows a "silver fox," an almost black-colored fox with white-tipped guard hairs beside a red fox. Both show a white tail tip. 

The silver fox is a color phase of the red fox (Vulpes vulpes). Most foxes used in the fur trade are red foxes. They are bred for various colorations. (FIF's red fox pelts are used in education. The silver fox pelt was rescued from a 1940s coat and the wild red fox was a car strike victim in 2005.)

 

gray fox; ancestor of the island fox

Black tail tip:

With a black stripe all the way down the back - you are looking at a gray fox. (If you are on the Channel Islands, it's an island fox.)

island fox on Catalina Island

 

kit fox; courtesy of K. Schafer
 

Just a black tail tip: Consider your location.

The Gemini foxes, the kit fox and the swift fox, seldom overlap in range. If you are located in parts of New Mexico and adjacent parts of Texas, big ears will separate the kit fox from the swift fox. In general, understanding the habitat where you see the fox will provide a clue as to the species you're observing.

No, definitive tail tip coloration: Arctic fox

Arctic foxes are easy to identify by their white coat in winter or their compact body size with small rounded ears and no contrasting marks on the tail.

Use this downloadable Identifying the Foxes of North America chart to help you know your local foxes. 


In this series of posts, we only touched the basics for each of the species covered. A list of research used in writing this project can be found at the end of each post. These resources are a great starting point for more information about the foxes that may live in your area. In addition, reading the abstracts of research articles provides wonderful insights into the latest information regarding a particular species. While the thought of wading through heavy scientist language may make your head spin, the abstract's concise language will slow that spin, allowing you the opportunity to glean useful information to assist in the better understanding of the fox you're interested in. It will also help sort fox fact from fiction.

Thank you to FIF Board Members - Mike Watling and Lara Brenner for this series on North American Foxes.

Series installments:

How is the Island Fox Unique?

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

 


Friday, March 12, 2021

The Island Fox's Origin - The Gray Fox

Gray fox (left) with two island foxes at CALM Zoo, Bakersfield CA

In previous posts we've introduced the red fox, the most widely distributed land carnivore on the planet, kit and swift foxes (the Gemini foxes), who inhabit the arid regions of North America, and the arctic fox, a true species of the north. In this installment of Foxes of North America, we conclude with the progenitor to the island fox: the gray fox.

island fox
 

As we've previously discussed on the Friends of the Island Fox website, the island fox descended from the gray fox (the island fox's "progenitor" or ancestor) between 7,000–9,000 years ago. In evolutionary time, that's relatively recent. When you examine the canid family tree, you'll find that the gray fox and its predecessors have been continuously inhabiting southern North America and Central America since the middle Miocene (10 million years ago). The genus Urocyon is the most primitive living canine lineage, closest to the origin of all canid species.

 

 

gray fox, Southern CA

Gray Fox: The Fox of the Forest

Gray foxes are commonly associated with deciduous or mixed coniferous forests. In contrast to the red fox, which prefers forest openings–meadows and farmlands–the gray fox prefers the cover of woodlands. Forested habitats allow this inconspicuous fox to elude predators in a most unusual way for a canid: it climbs trees! 

One set of traits retained from the gray fox's early divergence from other carnivores, (and one that other canids have lost) are its highly re-curved, semi-retractable claws and rotating forearms. These feline-like qualities allow a gray fox to hug trees much the same way a cat does. The gray fox's relatively short leg to body ratio lowers its center of gravity, aiding in balance and making it easier to use trees as a means of escape and to forage for bird eggs and fruits. (Island foxes have inherited this climbing ability.)

Found from southern Canada to northern Columbia and Venezuela, the gray fox is the only fox species to range across both North and South America. Gray foxes are absent from the northern plains and Rockies, as their short legs make it difficult to navigate areas with deep snow. In Southern Canada, gray foxes live in coniferous forests, where dense foliage may help mitigate the effects of heavy snowfall.

gray fox, photo courtesy of Jim Carretta
 

The scientific name for gray foxes, Urocyon cinereoargentus, breaks down as follows: Urocyon is Greek for "tailed dog" and cinereoargentus translates to "silvery gray," which accurately describes this handsomely dappled fox. (Island fox's scientific name.) Its underside is a cinnamon-rufous color and there is white fur on the face, throat, belly and hind legs. The tail has a black tip, which helps distinguish it from the red fox, whose tail is white tipped. There are distinct black spots on either side of the muzzle. The long bushy tail makes the gray fox appear larger than it really is. In general, they stand about 14 inches at the shoulder; weigh from 7–13 pounds and are 31–44 inches long from head to tail. (Compare to the island fox)

The gray fox is the most omnivorous of the wild canids. Just like the island fox, their varied diet consists of small mammals, birds, fruits, nuts and invertebrates such as Jerusalem crickets and grasshoppers. Their diet varies throughout the year based on prey availability, which allows them to adapt to changing environments.

island fox family allogrooming

While mostly solitary, gray foxes do spend time in pairs or in small family groups through out the year. More than any other fox species, gray foxes can be seen allogrooming, which is when individuals socially groom each other and their pups to remove ticks and pests. If you visit a Channel Island, you can see that this trait has been carried over to island foxes, as they are often observed grooming each other.

The gray fox's tendency to prefer areas with thick tree coverage makes this elusive species the least studied of the North American foxes. Overall, the gray fox population is healthy, and habitat loss doesn't appear to be impacting the species for now. Farmers who raise poultry feel that gray foxes are pests, but biologists claim this threat is overstated. On the contrary, gray foxes provide a benefit to humans by keeping rodent populations in check.

Indigenous peoples realized the value of their neighbor the gray fox and thus began a relationship that would lead to the evolution of the island fox.

Previous installments:

How is the Island Fox Unique?

Red Fox: Life on the Edge

Gemini Foxes: Kit Fox and Swift Fox

Arctic Fox: Fox of the Tundra

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.

 


Friday, March 05, 2021

Comparing the Island Fox and the Arctic Fox; The Fox of the Tundra

Santa Rosa Island fox, courtesy of NPS
 

In this installment of Foxes of North America, we'll look at the Arctic Fox. While the island fox lives on coastal islands that rarely experience a hint of snow, the arctic fox is a true species of the North and has adaptations that help it survive the harsh conditions of the polar regions.

Arctic fox; courtesy of Colby Brokvist: ColbyOutdoors Photography

Arctic Fox; The Fox of the Tundra

Tundra comes from the Finnish word tuntri, meaning treeless plain. The tundra is noted for its permafrost landscapes, extremely low temperatures, windswept plains, little precipitation and long dark winters. Yet, the arctic fox lives and reproduces successfully in this seemingly inhospitable environment. In North America, the arctic fox is found from western Alaska east across northern Canada. The arctic fox is a large North American fox species, weighing approximately 12 pounds.

Arctic fox; courtesy NPS
To survive extremely low temperatures that regularly reach -50 degrees F, the arctic fox has thick fur with two undercoats. This adaptation provides excellent insulation. (Compare to the island fox's fur.) A short muzzle, short ears and legs, as well as a rounded, compact body with a big bushy tail, also reduce heat loss. Arctic foxes have a special counter-circulating blood system that acts as a heat exchanger to cool, rather than warm, the blood flowing to their feet. Having cooler blood at their feet means less heat will be lost to the surrounding surfaces, thus requiring less energy for the fox to stay warm in frigid temperatures. In the summer, arctic foxes shed their long white coat and instead grow short, dark gray to bluish-brown fur.

Arctic fox in summer coat; courtesy NPS

The scientific name for the arctic fox is Vulpes lagopus. Vulpus is Latin for fox, while lagopus is Greek for "hairy foot". This is an accurate description of the fox's thickly furred pawpads; a trait also characteristic of rabbits and hares.


The tundra ecosystem has a simplified food web, because not many species can survive the harshness of the winters. For that reason, the diet of the arctic fox is less diverse than that of other fox species. Arctic foxes are capable predators of small prey, such as lemmings and voles. Individuals living along the coast take advantage of seabird populations, hunting birds and eggs. They also forage other available marine resources. Arctic foxes frequently follow polar bears and scavenge their leftover scraps. Arctic foxes are comfortable foraging on the pack ice as well. These winter weather foxes use the permafrost as a natural refrigerator to cache food in years of abundance for times when food is scarce.

Arctic fox; courtesy of Sean Beckett

Arctic foxes pair up in February and March and mate in April, which is late compared to their southern canid counterparts. (Island fox pups are born in April.) Arctic fox kits are typically born in May or June. They can have as many as 19 pups in a single litter. Extremely large litters of up to 22 kits have been observed. That's the largest litter size in order Carnivora! However, the average number of pups varies by local prey abundance and geographical area. More typical litter sizes for arctic foxes are 6–9 pups in inland areas and 3–6 pups in coastal populations. To handle such large litters, female arctic foxes have evolved 12–14 teats. Arctic foxes use dens primarily during the pup season (like island foxes). They build their dens in sandy soils where they can dig 2–3 feet before reaching the permafrost. Arctic foxes also make snow dens during blizzard conditions.

The fox of the tundra is an elegant creature that has adapted to survive in extremely cold environments. Arctic fox populations in North America are healthy and stable, so this species is not listed as threatened or endangered. That doesn't mean the foxes are without challenges. Red foxes have been expanding their range northward as a result of the warming climate, driving the arctic fox deeper into the polar regions. When red foxes encroach on arctic fox territory, the more aggressive red fox wins out. The extreme conditions of the northernmost arctic regions may limit the range expansion of the red fox, thus giving the arctic fox its best chance for long-term survival.

In the final installment of Foxes of North America, we will concluded with the progenitor of the island fox, the gray fox.

Series installments:

How is the Island Fox Unique?

Red Fox: Life on the Edge

Gemini Foxes: Kit Fox and Swift Fox;

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.

 

Friday, February 26, 2021

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 


 

 

Friday, February 19, 2021

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.


 

Friday, February 12, 2021

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

 

 


Friday, January 29, 2021

Fox Foto Friday - Island Foxes Healthy Inside and Out

 

While we're all stuck at home, the word from the islands is that island foxes are thriving. Across the Channel Islands biologists are reporting healthy looking individuals and a fair number of pups.

2020 was a normal rain year with a hot summer. Populations may have adjusted down from the record highs of 2019, but that is to be expected. The rains across the islands this week, will help increase resources for island foxes throughout 2021. What do island foxes eat?

During 2020 health checks, island foxes on Santa Cruz, Santa Rosa, San Miguel, San Clemente, and San Nicolas joined their cousins on Santa Catalina by being swabbed for their microbiome. Samples have arrived at the lab for DNA analysis. Find out more about Dr. DeCandia's island fox microbiome research.

To survive into the future, island foxes need to be healthy inside and out. That's why FIF is helping investigate the biodiversity in the microbes and bacteria on their skin and throughout their bodies.

Friday, November 20, 2020

Fox Foto Friday - A Slice of Fox Science

What is it?

 

This is a microscope slide with thin slices from the canine tooth of a deceased island fox. 

Researchers Stacy Baker and Juliann Schamel are looking at these thin slices through a canine tooth to see if they can discern annual growth layers. If so, this could provide an accurate way to age island foxes at death. Why is that important?

The sample slides from individual island foxes have come back from the lab in Montana. See more on the process and the annual layers.

Baker and Schamel will be analyzing the specimen slides from individuals with known ages. If the layers align with known ages, they will look at the specimens from individuals like M152 to try and determine how old these individual foxes were at death.

This important work is funded by Friends of the Island Fox through a grant from Safari West.

More about island fox research funded by Friends of the Island Fox and donors like you.

2020 FIF Research Grant recipient 

What We Do - FIF Research projects