About Island Fox

Santa Cruz Island fox pair; photo: Kevin Schaffer

Description: The island fox (Urocyon littoralis) is very small in size. Comparing island fox to other animals. It is 15-18% smaller than its ancestor, and closest relative, the gray fox (Urocyon cineroargenteus). Island fox size:

• Adults typically 12-13 inches high, to top of head
• 23-27 inches long from nose to tail tip
• weigh 2.5-6 lbs

Santa Catalina Island fox; photo: CIC

Males are slightly larger than females. Coloration is similar to the gray fox: grizzled gray along the top of the head and back, but with a greater amount of rufous or cinnamon coloring along the belly, neck and legs, and white along the cheeks and throat to the chest. The tail also has a darker black stripe along the top. More on coloring and variation.

Island foxes vary genetically and in coloration, size, muzzle shape and tail length from island to island. On the six California Channel Islands where island foxes are found, each population is considered a separate subspecies.

1. San Miguel Island fox (Urocyon littoralis littoralis) - typically second largest in size, shortest tail (average 15 vertebra)
2. Santa Rosa Island fox (Urocyon littoralis santarosae) - average the longest ears
3. Santa Cruz Island fox (Urocyon littoralis santacruzae) - typically smallest in size, shortest legs
4. Santa Catalina Island fox (Urocyon littoralis catalinae) - typically largest in size, longest tail
5. San Nicolas Island fox (Urocyon littoralis dickeyi) - may be lighter in color, typically longest legs, most number of bones in tail (average 22 vertebra)
6. San Clemente Island fox (Urocyon littoralis clementae)

Island Fox Fact Sheet (download pdf)

Where do they live? Island foxes live on six of the eight Channel Islands off the coast of Southern California and no where else in the world. See Habitat

How are island foxes different from other foxes? 

• Identifying North American foxes
• Red fox vs island fox
• Kit fox and swift fox vs island fox
• Arctic fox vs island fox
• Gray fox vs island fox
  

What do they eat? Island foxes are omnivorous, eating both plants and other animals. They eat a large amount of insects, some island deer mice, reptiles, and fruit from native plants. New evidence is showing marine resources may be important for island foxes. Their diet also changes with the seasons. See 2014 research on island fox diet. Whiskers provide information on diet.

Santa Cruz Island fox in tree; photo: Kathy Van Slyke

Survival Adaptations - Island foxes can run quickly over grasslands and hillsides to catch prey. They can turn their front paws inward in a way that helps them to be very good climbers. Island foxes will climb up into trees to find fruit and bird nests. Individual island foxes have even been seen climbing up into bald eagle nests to scavenge for dropped fish. Video of island fox in bald eagle nest. Island foxes have good vision, both day and night. Their sense of smell is excellent, helping them find food, identify other island foxes and define the lines between territories.

Behavior- Island foxes are active day and night. Each individual island fox has a territory that it marks with urine and scat. Pairs tend to mate for life, and a mated male and female will have overlapping territories. Island foxes protect their territories and sometimes they can be heard barking or yipping at other foxes coming into their territory. See video of barking island fox. Territorial disputes can be serious, injury from these disputes can include ripped and torn ears, leg wounds and even death.

Photos of interaction between two unrelated adult island foxes.

island fox pup; photo: NPS volunteer Inge Rose

Reproduction - Island foxes breed once a year and are the only known canine species to exhibit induced ovulation. Pairs come together in late winter, find a den location and mate between January and March. Typically, one to five pups are born in late April. The number of pups is related to available resources. During drought years reduced food availability reduced the number of pups being born. There is evidence that island foxes on the southern islands may be reproducing two months earlier as the climate warms. Pups are small (the size of two AA batteries) at birth. They stay in the den, cared for by their parents until early June. Over the summer, both parents teach the pups to hunt and find food. Island fox pups grow up fast. See video of pups. When September arrives, most pups head out to find their own territory. Female pups may stay near their parents’ territory, while male pups tend to travel a distance before setting up their own territory.

Keystone Species - The island fox is considered a “keystone species” because without it, the natural web of life in the island ecosystem begins to collapse. Other species may be negatively impacted to the point they might not survive. Without the island fox, island deer mice begin to over consume plant resources causing population explosions and starvation events that cause population crashes. When island deer mouse populations are high, the mice tend to prey on the eggs of low nesting birds. Without the island fox, island spotted skunk populations increase. The spotted skunks then prey on endangered sea birds nesting on the islands. Many native island plants, like the Catalina cherry, toyon and manzanita, rely on the island fox to swallow and then disperse their seeds. Seeds in fox scat. Insects and bird populations are dependent on the plants that the island fox reseeds. The kelp forests surrounding the Channel Islands benefit from healthy plant communities that reduce erosion and silty run-off from the islands. Healthy kelp forests provide a nursery for many important fish and crustacean species that benefit bald eagles and people. Even the marine ecosystem benefits from the island fox.

How did foxes get to the Channel Islands?  This small species of fox has always lived on the Channel Islands. How their ancestors arrived on the islands continues to be explored by researchers. The two theories on island fox origins. 2015 Mitochondrial DNA data suggesting short period of evolution.

Are island foxes endangered?  Island foxes were considered an U.S. Endangered Species on four islands: San Miguel, Santa Rosa, Santa Cruz and Santa Catalina Islands from 2004 thru 2016. August 2016, the USFWS officially removed island foxes from the Endangered Species List. The state of California still considers all island foxes a species of special concern.

Disease on Santa Catalina Island - The island foxes on Santa Catalina became endangered when a wild North American raccoon was accidentally transported on a boat and escaped onto the island in 1998. Canine distemper virus, a fatal dog disease, was passed from this raccoon to the Catalina island foxes. By 2000, over 90% of the Catalina population had died from the distemper virus. Disease on the islands. Threat from distemper returns in 2021

An Ecosystem Out of Balance on the Northern Islands - In the mid-1990s biologists on the northern islands of San Miguel, Santa Rosa and Santa Cruz began to notice a decline in island fox populations. By 2000, the northern populations were crashing toward extinction:

• San Miguel Island fox - 1994 (est. 450 foxes); 2000 (only 15 individuals remained)
• Santa Rosa Island fox  - 1994 (est. 1,780 foxes); 2000 (only 15 individuals remained)
• Santa Cruz Island fox - 1994 (est. 1,465); 2002 (~62 individuals remained)

bald eagle on Santa Cruz Island; photo: Peter Sharpe

This rapid population decline was due to an imbalance in the ecosystem. The island fox is the largest mammal native to the islands; it is the top terrestrial predator. It did not know how to protect itself when a new predator came to the northern islands.

Historically, bald eagles lived across the Channel Islands. This large bird of prey specializes in eating fish and sea birds and did not prey on the island fox. As a territorial bird, it kept other eagles from nesting on the islands.

After WWII, the widespread use of the chemical insecticide DDT introduced this toxin into local watersheds and the marine environment. DDT caused the eagles to lay eggs with thin shells, which crushed under the incubating parent.  DDT and the Bald Eagle. By the 1960s there were no bald eagles on the Channel Islands.

Large scale ranching on the islands introduced plant-eating animals: goats, sheep, pigs, as well as deer and elk for hunting. These animals ate away the native plants that the island fox depended on. Ranching had limited success on the islands and the domestic animals became feral or wild. The young pigs, goats and deer, were all potential food sources for another large bird of prey. After DDT was banned in the 1970s and ecosystems began to recover, golden eagles moved out to the northern Channel Islands to prey on the introduced animals and eventually, the island fox. From 1994-2000, golden eagle predation on island foxes was extreme. The golden eagle was eating the island fox into extinction.

Conservation Efforts - Rapid response on the part of land managers at the Channel Islands National Park, Nature Conservancy and Catalina Island Conservancy, government agencies and public and private organizations saved the four endangered island fox populations from extinction. What conservation steps were taken?

• The first action was to bring surviving island foxes into protective captive breeding facilities on each island. Captive breeding saved these populations. As threats to the island fox were removed, individual animals were released. As of November 2008, captive breeding ended and all healthy island foxes were returned back into the wild. M67 Release
• Over 40 golden eagles were captured and relocated to northern California.
• Bald eagles were reintroduced to the Channel Islands and as of 2006 are again breeding naturally on the islands. Their current population is approximately 60 individuals.
• Feral goats, pigs and sheep, as well as introduced mule deer and elk have been removed from the northern Channel Islands. Feral cats have been relocated from San Nicolas Island to a sanctuary near San Diego. Introduced bison numbers are managed on Santa Catalina Island.
• Introduced plant species are being removed from the islands and native plants reintroduced. Removing invasive plants on Santa Cruz Island.
• Island foxes are monitored with identification microchips and radio tracking collars, vaccinated against canine distemper and rabies viruses, counted annually and given health checks. On some islands foxes are tested for exposure to viruses.
  
• Food lockers and signs make island visitors aware of island foxes and the importance of not feeding them.
• Open trash bins on Santa Catalina Island pose a threat of entrapment. Island foxes become trapped in bins and the attraction of food in open bins encourages them to cross roads more frequently, increasing the number hit by cars. Fox-Saver Bins on Catalina Island
• Education representative island foxes are cared for at several facilities. Where Can I See an Island Fox?

San Clemente Island fox; photo: Paul Bronstein

What is the Current Status? As of August 2016, there are no island fox populations listed as Endangered under the Endangered Species Act.  In 2020 all island fox populations were stable, but continued drought in 2021 could impact island fox survival. Wildfire now poses a greater threat across the islands. Increasing parasites, especially ticks and tick-borne disease, are posing new threats to island fox and human health. See the summary of 2020 / 2021 status.

See 2013 presentation given by National Park biologist Tim Coonan for general information on the historic decline of island foxes in 1994-2000.   

The San Miguel Island population is considered recovered, but drought impacts and a new parasite have caused a decline from the 2015 high population level. See 2015/2016 status summary. Land managers continue to monitor populations, to watch for introduced disease and evaluate the impact of the multi-year drought. The island foxes on the two islands managed by the U.S. Navy–San Clemente and San Nicolas–have never been listed as federally Endangered. The San Nicolas population took an unexpected decline thru 2013-2014 . The population has stabilized and drought impacts on food resources are now believed to have been the major cause for the decline.

Sources:

• Booker, M. (2017, May 16).  San Clemente Island Update.  Paper presented at 2017 Annual Meeting, Island Fox Conservation Working Group, Santa Barbara, CA.
• Collins, P. W. (1980). Food habits of the island fox (Urocyon littoralis littoralis) on San Miguel Island, California. In proceedings of The Second Conference on Scientific Research in the National Parks: Vol. 12. Terrestrial biology, zoology (NTIS. Publication No. 81-100133, pp. 152-164). Washington DC: National Park Service.
• Coonan, T. (2003). Recovery strategy for island foxes (Urocyon littoralis) on the northern Channel Islands. Channel Island National Park, Ventura, CA: National Park Service.
• Shaskey, L. (2017, May 16, a). San Miguel Island Fox Update. Paper presented at 2017 Annual Meeting, Island Fox Conservation Working Group, Santa Barbara, CA.
• Shaskey, L. (2017, May 16, b).  Santa Rosa Island Update.  Paper presented at 2017 Annual Meeting, Island Fox Conservation Working Group, Santa Barbara, CA.
• Coonan, T. J., Schwemm, C.A., and Garcelon, D. K. (2010). Decline and recovery of the island fox; A case study for population recovery. United Kingdom: University Press Cambridge.
• Ferrara, F. (2017, May 16)  San Nicolas Island Update.   Paper presented at 2017 Annual Meeting, Island Fox Conservation Working Group, Santa Barbara, CA.
• Hudgens, B. R. (2013, June 11). San Nicolas Island fox update. Paper presented at Sixteenth Annual Meeting of the Island Fox Working Group, Ventura, CA.
• King, J. (2017, May 16).  Santa Catalina Island Update.  Paper presented at 2017 Annual Meeting, Island Fox Conservation Working Group, Santa Barbara, CA.
• King, J. (2013, June 11). Santa Catalina Island fox update. Paper presented at Sixteenth Annual Meeting of the Island Fox Working Group, Ventura, CA.
• Moore, C. M., and Collins, P. W. (1995, June 23). no. 489, Urocyon littoralis. Mammalian Species, 1-7.
• Roemer, G. W., Coonan, T. J., Garcelon, D. K., Bascompte, J., and Laughrin, L. (2001). Feral pigs facilitate hyperpredation by golden eagles and indirectly cause the decline of the island fox. Animal Conservation, 4, 307-318.
• United States Fish and Wildlife Service [USFW]. (2005). Final determination concerning critical habitat for the San Miguel Island fox, Santa Rosa Island fox, Santa Cruz Island fox, and Santa Catalina Island fox: California/Nevada (Region 8) [70 FR 67924 67929].  Retrieved April 6, 2009, from: http://ecos.fws.gov/speciesProfile/SpeciesReport.do?spcode=A08L

Updated 5/24/21