The Island Fox Returns
This tiny fox’s recovery is probably the fastest rebound of any land mammal in the history of the Endangered Species Act
If you come out to Santa Cruz Island today, you’re virtually guaranteed a sighting of an endangered island fox, the little rascals bounding across the largest of California’s Channel Islands. That wasn’t the case 15 years ago when the small fox, which is native to six of the eight Channel Islands and is the chain’s largest land mammal, teetered on the brink of extinction.
At about 18 to 20 inches long and weighing anything from 2.2 to 6 pounds, the island fox (Urocyon littoralis) is probably the smallest fox in North America. The fox, which shares the same genus as the mainland gray fox, is thought to have “rafted” to the northern Catalina islands some 10,400 to 16,000 years ago. Evolutionary biologists say they shrank in size over the ages in order to adapt to the limited resources available in the island environment. There are six subspecies of the island fox, each of which is native to a specific Channel Island, and which evolved there independently of the others.
The foxes thrived on the islands until about two decades ago when they began to be preyed on by golden eagles. Back then a 5,000 strong feral pig population had lured more than 40 golden eagles from the California mainland. The decline of the local bald eagle population in the 1950s and 60s due to persecution by humans and exposure to organochlorine chemicals such as DDT, may have made it easier for the golden eagles to settle on the islands. The bald eagle, which subsisted on fish, would have deterred the golden eagle from settling on the islands. In any case, the new-to-the islands raptors, which colonized the northern islands of the Channel Islands National Park, soon realized it was easier to hunt island foxes than the scruffy swine. (The golden eagle is four times the size of the island fox.)
By 1999, roughly 55 island foxes were left on Santa Cruz Island, looking over their shoulders, wary about their time being up. Island fox populations on Santa Rosa and San Miguel Islands also plummeted due to golden eagle predation, and an outbreak of canine distemper in 1998 killed off about 90 percent of Santa Catalina's fox population. Reduced food supply and habitat degradation due to other introduced species, such as feral cats, pigs, sheep, goats, and bison, also had a negative effect on fox populations. The US Navy’s trapping and killing of the animals on San Clemente Island in an effort to save the severely endangered San Clemente Island loggerhead shrike (which were being preyed on by the fox) too, played a role
The loss of fox populations on any of the islands would mean that that particular subspecies would be gone forever.
Faced with the Island fox’s rapidly dwindling numbers, conservation partners such as the National Parks Service, The Nature Conservancy, The Institute for Wildlife Studies, and the US Fish and Wildlife Service (USFWS) began to implement efforts rebuild fox populations on the islands. In 2004, four island fox subspecies – the Santa Cruz Island fox, Santa Rosa Island fox, San Miguel Island fox and the Santa Catalina Island fox – were federally protected as endangered species.
A captive breeding program, which was initiated in 1999 on each island and ended in 2008, played an integral role in recovery efforts. All captive-bred foxes were returned to the wild and vaccinated to prevent the spread of canine distemper. Additionally, golden eagles were trapped and relocated to the California mainland. The feral pig population was eradicated from Santa Cruz Island, and bald eagles were re-established to their historic territories. Meanwhile, the US Navy began to use more humane predator management strategies, such as trapping and holding foxes during the shrike breeding season, installing electric fences around shrike habitats, and equipping foxes with shock collars.
As a result of these initiatives, the cinnamon colored fox’s numbers soon began to look up.
Santa Cruz, one the most biodiverse islands off the California coast, now has about 1,200 island foxes; San Miguel Island is currently at carrying capacity with about 500 of the animals; and the fox population at Santa Rosa Island is at around 700.
“Today there is no hint of golden eagle predation,” says Tim Coonan, terrestrial biologist on the Channel Islands National Park. “It’s great to be where we are.”
In 2013, the International Union for Conservation of Nature changed the listing of the entire species from “critically endangered” to “near threatened. ”
The recovery of the island fox is probably the fastest rebound of any land mammal in the history of the Endangered Species Act. “The island fox will probably be delisted within 2 years,” Coonan says. “Endangered species typically average 25 years on the list. It’s really rare to get one off. Everyone sees a win, win with this though.”
Chuck Graham is a freelance writer and photographer in Carpinteria, CA.