Sharp Decline in Number of Island Foxes Prompts Study

Worried by the dramatic decline in the population of foxes on two islands off the Ventura County coast, federal scientists are studying the rare breed on Santa Cruz Island to see if they should expand a captive-breeding program there.

Over the past six years, the number of island foxes found on two islands in the Channel Islands National Park--San Miguel and Santa Rosa--has decreased by more than 90%, scientists said, making the house-cat-sized fox one of North America’s most imperiled canines.

Concern for the future of island foxes has reached such heights that, along with starting the study on Santa Cruz, scientists flew a team of veterinarians last weekend to Santa Rosa Island to treat a cancer-stricken female fox who might not have lived through the next breeding cycle.

Because Santa Cruz was a private island for so long, scientists have little idea of just how many foxes--which have become easy pickings for recent arrivals of golden eagles--exist on the chain’s largest island.

They need to know if they must remove foxes from the wild and place them in captivity, as they have on the two other islands. About 75% of Santa Cruz is owned by the Nature Conservancy, a nonprofit group dedicated to preserving species and land. In August, the organization donated about 8,500 acres of the rugged island to Channel Islands National Park and is now working with park biologists to track the threatened foxes.

“We don’t know where we stand,” said Lynn Lozier, the conservancy’s Santa Cruz Island project director. “We need to know how many foxes we have, where they are and how close they are to each other.”

Researchers expect to find anywhere from 80 to 150 foxes in the wild on Santa Cruz. On Santa Rosa Island, 22 foxes are captive and as many as five roam wild. On San Miguel, one fox remains wild, eluding scientists who are trying to track it down, and 16 are captive.

On Santa Rosa, the female fox scientists call A-7015 was anesthetized, placed on an outdoor picnic table and treated with laser surgery Saturday to remove a tumor on her palate. The sarcoma tumor, diagnosed about two weeks ago, could kill her before she breeds, but biologists considered the breeding of new foxes so important they chartered a $1,000 flight to bring out the volunteer doctors.

“The bottom line is we don’t know how much time they bought her. A couple months or half a year?” said Tim Coonan, a park biologist. “Hopefully, she’ll recover and go back to courtship with her male.”

Foxes pair up during a mating season that begins with courtship in October, continues with breeding in early March and ends when a litter is born in mid- to late April. If A-7015 dies, her mate would most likely not breed with another female.

She is one of nine females on Santa Rosa to pair up with a male, and she had three pups last year, which Coonan called a good track record.

“When you know the numbers are this low, then every individual is critical,” said Sam Dover, the Santa Barbara Zoo veterinarian who performed the surgery. “It’s a matter of seeing how she responds.”

Cancer is as common among foxes as it is among people, Dover said. But, Coonan said, this is the only cancer he’s seen in thousands of island foxes.

The female fox is now recuperating from surgery in a pen on Santa Rosa Island and eating soft dog food, rather than the typical kibble. Coonan said scientists may have to hand-raise her litter if she doesn’t recover from the cancer.

“Hopefully, she’ll be feeling much better,” he said.

Man-made changes to the island’s environment, started when settlers arrived in the 19th century, still threaten the foxes. Sweet-natured and naive, the toy-like animals have been sheltered so long that they aren’t aware they have predators.

Until a decade ago foxes flourished on the island. But golden eagles, drawn recently by the feral descendants of pigs brought by settlers a hundred years ago, have chosen the fox as a quick snack and decimated their ranks, scientists say. Biologists are trying to remove both the eagles and pigs, in hopes of restoring the islands to their condition before Spanish explorers settled there.

The Nature Conservancy and the parks service are conducting a $50,000 study on the foxes, to be paid for by oil company BP Amoco.

On Santa Cruz, scientists bait and trap foxes individually and track them as they move across the island. Experts are eagerly awaiting study results, expected by midsummer, because they are not sure how long the foxes can last.

“We still don’t know if they’ll survive or not,” said Tim Setnicka, Channel Islands National Park’s superintendent. “We’re where medicine was in the late 1800s.”