Endangered species news hardly ever comes with happy endings. But on a popular tourist island off the California coast, a frankly endearing wildlife species has come back from the verge of extinction in the last decade with a little help from its friends.
The Catalina island fox is one of six subspecies of Urocyon littoralis that inhabit the Channel Islands off the Southern California coast. Like many island species, island foxes are in trouble. Foxes on Santa Cruz, San Miguel, and Santa Rosa islands have been in decline since the 1990s, mainly due to predation by golden eagles.
But it was an outbreak of distemper 15 years ago that nearly wiped out Catalina's foxes: a population of something like 1,300 foxes crashed to around 100 individuals. A strain of distemper usually found in raccoons had made it to Catalina somehow. Vaccines were ineffective: the distemper shots administered to pets would actually infect foxes with the highly contagious virus. Things looked bleak.
Island foxes are smaller than their mainland gray fox cousins. The Catalina island fox, the largest of the six subspecies, is about the size of a small housecat. The foxes' varied diet consists of rodents and other small mammals, birds and eggs, shellfish, and lots of fruit.
Listed as Threatened under the California Endangered Species Act since 1971, the Catalina island fox was listed by the feds as Endangered in 2004, along with its cousins on the three other islands where its populations had crashed. That listing came five years after the fox's numbers took a nosedive, in response to a suit by the Center for Biological Diversity and others.
The virus can survive in mainland wildlife populations without killing entire species off, but that's because mainland animals are continually exposed to the disease and have evolved resistance. Stuck out on their island paradise twenty miles off Long Beach, Catalina island foxes have had no reason to evolve the ability to survive distemper.
California's Channel Islands are unique evolutionary laboratories. The islands have never been connected to the mainland even during the Ice Ages, when sea level was much lower. Anything that lives on the islands is there because it or its ancestors crossed at least ten miles of seawater.
The word "isolate" has its etymological origins in the Latin word "insula," which means "island." An animal or plant that finds itself on an island farther from the mainland than it can easily fly, swim, or disperse its seed finds itself isolated in an evolutionary sense.
Isolated from their mainland kin, many Channel Islands plants and animals have evolved into forms distinct from their mainland relatives. The archipelago as a whole is home to more than 140 species or subspecies that are endemic to the island -- they're found nowhere else. (Unless, that is, people have deliberately moved them, as is the case with quite a few of the islands' endemic plants.)
Santa Catalina Island is home to around 60 of these endemic species or subspecies. Some of them are perilously close to extinction. Take for instance the Catalina mahogany, Cercocarpus traskiae, with just seven individual plants remaining in the wild. Or the Catalina manzanita, Arctostaphylos catalinae, for which the California Native Plant Society has just nine locations on record.
In most of California, packing that many rare species into a few dozen square miles would be a recipe for extinction as developers displace habitat for the sake of economic development. But the Channel Islands aren't like the rest of California. Five of the eight islands are under the protection of the National Park Service as Channel Islands National Park. San Nicolas and San Clemente islands are property of the U.S. Navy, which uses them as testing sites. And though Catalina hosts the only permanent civilian population in the archipelago, the vast majority of the island is managed for conservation by the non-profit Catalina Island Conservancy.
And it's the Catalina Island Conservancy that gets the lion's share of the credit for the Catalina island fox's continued existence on the planet.
No one knows how foxes got to Catalina, whether by rafting on wrack from a flood on the L.A. River or brought along as semi-domesticated companions by people. Though you can find loads of references to the Catalina island fox having showed up on the island as recently as a few hundred years ago, the Conservancy's Chief Conservation Officer John Mack says ongoing research is pushing that date back. "We keep finding older and older evidence of foxes on Catalina," Mack says. "Native burial sites from up to 8,000 years ago include foxes. They may have been beloved pets."
We also don't know how the raccoon strain of the canine distemper virus made it to Avalon, Catalina's main settlement. Raccoons don't have an established population on the island, though every now and then one will stow away on a pleasure craft, attracted by improperly stored food. Or perhaps a domestic dog contracted the raccoon distemper strain on the mainland, then brought it to Avalon. However the virus came ashore, it started spreading though the fox population on the east end of the island. Within a very short time, more than 93 percent of the total world supply of Catalina island foxes had died of distemper.
An accident of geography proved a boon to the subspecies' survival. Catalina is very nearly two islands; the island's East and West ends are connected by a low isthmus only about 2,000 feet wide and below fifty feet in elevation. The settlement of Two Harbors, with a couple hundred permanent residents, occupies the isthmus. Two Harbors is thus an effective barrier to fox migration.
Cutting off wildlife connectivity corridors is a bad thing in general, but Two Harbors did keep foxes infected with distemper from wandering over to the West End of Catalina, meaning that West End foxes were mainly isolated from the virus.
That was a break for the subspecies. The Catalina Island Conservancy started a captive breeding and translocation program with the healthy West End population, using the resulting young foxes to repopulate places on the East End where the foxes had died out.
A distemper vaccine for dogs has been available for some decades. But that vaccine uses a modified live virus. Foxes are susceptible to infection from the virus used in the standard veterinary distemper vaccine. "If we used the normal distemper vaccine for pet dogs we could actually introduce distemper into the fox population," notes the Conservancy's senior wildlife biologist Julie King.
King spoke to a group of reporters in the hills above Avalon on Friday as she checked fox traps set the previous afternoon, part of a yearly monitoring program. Each year the Conservancy traps, examines, and records the condition of around 300 Catalina island foxes. That's three times the number of island foxes that survived the distemper outbreak at the turn of the century, and just a fifth of the estimated 1,500 or so individuals that now inhabit Catalina.
King notes that the foxes got another break, this one through the misfortune of another species -- the black-footed ferret of the Great Plains. Nearly wiped out by habitat loss and plague-driven losses of the prairie dogs that make up its main food source, the ferret was actually considered extinct until a Wyoming ranch dog brought one to its master in 1979. A small nearby population was the salvation of the species, which is now back up to about 1,000 individuals.
Like the foxes, the ferret is extremely susceptible both to canine distemper and to infection from the standard distemper vaccine. Wildlife biologists developed a distemper vaccine they could use safely on the ferrets, and when scientists working for the Institute for Wildlife Studies tested it on island foxes, it proved a safe and effective way to protect them from the disease that had nearly done them in.
The distemper vaccine and a standard rabies shot are now part of the foxes' annual checkup regimen on Catalina. King and her colleagues pad custom-built humane traps with grass and provide commercial cat food and a powerful loganberry-scented lure as bait. If a trap turns out to have a (usually very testy) fox inside, the biologists scan the fox for an implanted microchip to identify the fox. If the fox doesn't have a chip, they implant one. Each animal is checked for dental health; ectoparasites such as fleas, ticks, and earmites; general physical condition; and exposure to distemper -- that last by way of a blood draw. Minor veterinary care is provided if necessary: on Friday, King removed a foxtail awn from the inner ear of a young male.
A few foxes aren't inoculated against distemper: instead, they're fitted with a small radio collar and released. The collar's signals change when the transmitter is stationary for more than a day or so, signaling that the fox has likely died. On recovery the carcass is tested for distemper, and the results give scientists a hint as to whether the disease is still causing mortality in the wild population.
As island foxes have evolved without larger predators, they lack the wariness of their mainland cousins. That means that being handled by biologists doesn't stress them out nearly as much as it might with other animals. King and her colleagues don't have to sedate the foxes to examine them, which is easier on the foxes and biologists both -- though the biologists will put masks on the foxes to calm them during the blood draw and ear exam. The whole routine from retrieving the traps to letting the foxes go and re-setting the trap for the next day's work can take King just 10 to 15 minutes -- when she's not explaining each step to a group of reporters, that is.
And the data show the foxes aren't particularly traumatized by the experience, as some will return for a free meal of cat food and loganberry lure on consecutive days.
The result of the captive breeding and vaccination program? There are now more island foxes on Catalina than there were before the distemper outbreak: about 1,500 in 2011 and 2012. A drought this year will likely depress the 2013 count somewhat: King says far fewer foxes less that a year old are showing up in traps this year, suggesting that the drought and consequent lack of food may have led to breeding season failures as pups starved.
That may well turn out to be part of the foxes' normal population cycles, but the Conservancy's President and CEO Ann Muscat points out that the subspecies is still endangered, and that new threats to the fox can emerge at any time. The Conservancy can't control whether dogs brought to Catalina are distemper-free, and though visitors and residents are asked to keep their dogs on leash, a day in Avalon during the off-season will reveal that dozens of dogs are breaking that rule at any given moment.
Distemper is just one of the threats facing island foxes throughout the islands. Golden eagles moving in over the last half-century have taken a huge toll on foxes on other islands. Up until 1960 or so bald eagles kept the goldens out, and bald eagles eat fish rather than fox. But bald eagles declined during the DDT years, and conservationists now struggle to rebuild those numbers and move golden eagles to more suitable places on the mainland. Introduced feral animals eat or compete with the foxes, and fire and climate change pose significant threats.
And ironically, one island's fox population poses its own threat to another island endemic, the San Clemente Island loggerhead shrike.
"This is what conservation is all about in a lived landscape," says Muscat. "You're never finished."