by Robin Meadows
Pity the island fox. Found on only six of California's Channel Islands, this small, docile cousin of the mainland gray fox seemed to be doing fine until the mid-1990s. Then everything went wrong at once. A decade of trouble, from disease to conflicts with other protected species, left the island fox (Urocyon littoralis) critically endangered.
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| The National Park Service radiocollared this fox in 1998. She was killed by a golden eagle in 1999. (Tim Coonan/NPS) |
Right now the biggest problem is that the foxes on San Miguel, Santa Rosa, and Santa Cruz islands are being picked off by golden eagles (Aquila chrysaetos), which are difficult to control because they are protected themselves. No one expects saving at-risk species to be easy. But does it have to be this hard?
Yes and no. Yes, from a political standpoint: Resolving conflicts between protected species is legally murky and emotionally charged. And no, from a purely biological standpoint: Golden eagles must be removed for the foxes to recover. But nobody wants to give the order to kill the few eagles that have eluded live capture and relocation.
Golden eagles are far from the only threat to the island fox. Habitat loss and degradation are huge problems on the Channel Islands. In addition, foxes on San Clemente Island were controlled to protect a critically endangered subspecies of loggerhead shrike (Lanius ludovicianus mearnsi) that is also unique to the island, while those on Santa Catalina Island were decimated by canine distemper that was presumably introduced by a dog. But life is getting better for the foxes on these two islands, while those on the three islands with golden eagles remain in extreme peril.
Island Fox History, Natural
and Otherwise
The island fox population has gone from small to smaller
in the last ten years, down from an estimated 5,200
in 1994 to only about 1,300 today. The number of island
foxes would be small even under the best of circumstances
because they live in such a small area: The six Channel
islands with foxes range from about 15 to 100 square
miles. These islands lie from 19 to 60 miles off the
coast of southern California, with three to the north
(San Miguel, Santa Rosa, and Santa Cruz) and three to
the south (San Nicolas, San Clemente, and Santa Catalina).
Each of these islands has a unique fox subspecies named for it. In addition, the islands—and the fox subspecies on them—are under various jurisdictions, including the U.S. Navy, the National Park Service (NPS), The Nature Conservancy, and the Catalina Island Conservancy.
Island foxes evolved from gray foxes, which are thought to have colonized the Channel Islands roughly 20,000 years ago. Back then, the northernmost islands were easier to reach because the sea level was much lower, exposing now-submerged parts of the islands that are connected to each other and that are closer to the mainland. Today’s three northernmost islands then formed one larger island that was about four miles off the coast. The foxes are thought to have spread to the southernmost Channel Islands beginning about 10,000 years ago, probably as pets or totems of the Chumash Indians who lived on the islands and along parts of the California coast.
Weighing between four and five pounds, island foxes are only one-third the size of the mainland gray foxes they evolved from, and are far less wary, to the point that they seem to have no fear of people. This is not surprising because island foxes are the top terrestrial predators native to the Channel Islands and so historically had nothing to fear. Another reason the foxes have done so well on the islands is that they thrive in a variety of habitats, from grasslands to shrublands to oak forests, and eat a wide variety of food, from mice to large insects to fruit.
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| A Channel Island fox pup from a captive breeding program. (Don Jones/NPS) |
When European settlers came to the Channel Islands two centuries ago, they changed the ecosystem radically. Perhaps the biggest change was that they introduced livestock and game animals that grazed or browsed native plants to nubs, opening the way for the non-native grasslands that have taken over much of the islands and shrinking the already-small habitat available to the foxes.
State-listed as threatened in 1971, island foxes did relatively well until recently. Populations on most of the islands seemed stable and efforts were underway to begin eradicating non-native herbivores, such as sheep and goats, and restoring native plants. But in the 1990s, trouble began hitting the foxes on one island after another, and 1999 was a particularly bad year for them. Distemper hit Santa Catalina Island, the foxes were included in predator-control programs to protect the loggerhead shrike on San Clemente Island, and island fox populations had become tiny or extinct in the wild on the northern Channel Islands.
The Simplest Fix
The 1999 distemper outbreak on Santa Catalina Island
literally decimated the island fox population, cutting
it from about 1,300 to fewer than 200. The distemper
virus was probably introduced by an unvaccinated pet
dog—Santa Catalina is a popular tourist destination
and its main town, Avalon, has many dogs.
The Santa Catalina fox is under the stewardship of
the Catalina Island Conservancy, which owns four-fifths
of the 76-square-mile island and was founded in 1972
to preserve and provide public access to the island's
natural heritage. In 2000, the Catalina Island Conservancy
and the Institute for Wildlife Studies, a California
nonprofit conservation organization, began breeding
Catalina foxes in captivity. To protect the foxes from
future distemper outbreaks, the captive adults and captive-born
pups are vaccinated against canine distemper. In 2002,
the Catalina fox population was estimated at 215, with
15 captive-born pups scheduled for release in 2003.
The Best Outlook
The foxes are doing best on the islands under the Navy's
jurisdiction, San Nicolas and San Clemente. These two
populations are the biggest at perhaps 500 and 400,
respectively. However, while the San Nicolas fox is
stable, the San Clemente fox appears to have been declining
and no one is exactly sure why.
One difficulty, now resolved as far as the foxes are concerned, is that the island is also the only home of the San Clemente loggerhead shrike, which is one of the most endangered birds in the world. The Navy began breeding the shrike in captivity in 1991, but even so, there were only about a dozen in the mid-1990s. The foxes were among the suspected causes because they had been observed preying on nestling shrikes in the wild.
In the late 1990s the Navy worked with the U.S. Fish & Wildlife Service (USFWS) to develop a predator control program that included killing, relocating, and temporarily capturing San Clemente foxes during the shrike-breeding season. The rationale was that surveys showed that the fox population was then stable, while the shrike was anything but. "In the minds of most, the precariousness of the shrike necessitated aggressive actions," says Jan Larson, Director of the Natural Resources Program for Navy Region Southwest. As a safeguard, the program also included monitoring the foxes to make sure one native species wasn’t being protected at the expense of another.
In 1999, 32 island foxes were killed, 14 were shipped to zoos, and 49 were held in captivity on the island during the shrike-nesting season. In 2000, 71 island foxes were temporarily caged on the island. In addition, the predator control program included keeping the foxes away from shrike nesting grounds with electrical fences, and, for repeat offenders, shock collars.
Then the monitoring suggested that the foxes were declining. "The reason was unknown but it sent up a red flag," says U.S. Navy biologist Kelly Brock, who was a Smithsonian’s National Zoo post-doctoral intern in the early 1990s. However, it makes sense that the fox control program was a likely factor. The foxes and the shrikes breed at the same time, which means that all of the measures intended to reduce fox predation also reduced the size of the fox breeding population. On top of probably being bad for the foxes, it turned out that controlling them probably didn't even do the shrikes much good—further nest surveillance failed to show that the foxes were major predators of shrike nestlings.
The fox control program was scaled back on San Clemente Island in 2002 and was abandoned in 2003. Today only non-native predators, notably feral cats, mice, and rats are controlled there. The word is still out on how the foxes are doing there now, but the shrikes are definitely doing better, with at least 75 in the wild and 60 in captivity.
The Biggest Problem
The foxes are doing worst on the three northern islands,
which are in Channel Islands National Park. The Santa
Cruz Island fox has declined by 90 percent since 1993,
from 1,300 to about 100. Worse, the San Miguel and Santa
Rosa island foxes are extinct in the wild, down from
450 and 1,500, respectively, in 1994. In 1999 the NPS
began captive-breeding the foxes and today there are
25 Santa Cruz foxes, 38 San Miguel foxes, and 46 Santa
Rosa foxes in captivity.
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| A wild fox caught during the National Park Service's annual monitoring. (Tim Coonan/NPS) |
The most immediate problem for these foxes is that they are being eaten by golden eagles. These raptors historically were transient visitors to the Channel Islands but began visiting more often in the mid-1990s and by 1999 they had been nesting on Santa Cruz Island for some time. Because island foxes are not wary, they are easy pickings for the eagles. Moreover, island foxes are more likely to be out during the day than mainland gray foxes, but they have fewer places to hide because historic sheep grazing replaced native shrublands with non-native grasslands.
Knowing why golden eagles started nesting on Santa Cruz Island is part of the key to getting rid of them. The foxes are not the reason, because even at their most abundant there were not enough of them to support breeding eagles. Gary Roemer, an assistant professor at New Mexico State University, Las Cruces, has linked the nesting eagles to non-native pigs (Sus scrofa) on Santa Cruz Island: The abundant piglets provide a steady food supply for the eagles and their young. While the foxes are not their primary food source, golden eagles readily prey on them too—and as the eagle population went up, the fox population went down.
Golden Eagles: Protected but
Not Endangered
Initially, the fix for the northern island foxes seemed
straightforward. "In 1999 we had a simple model:
Remove the golden eagles and breed the foxes in captivity,"
says Tim Coonan, a biologist at Channel Islands National
Park.
But applying this model has been anything but simple. Golden eagles are hard to control because they are protected by the Bald and Golden Eagle Protection Act as well as the Migratory Bird Treaty Act. "It's a sticky situation with the golden eagle protected by two federal laws," says Roemer, who is also the World Conservation Union (IUCN) island fox coordinator. Although once at risk, golden eagles are now doing well in much of western North America.
So far, the NPS’ approach has been to try to capture and relocate the golden eagles from the islands. Adults have been trapped using radio-controlled bow nets set over bait, and eaglets have been caught by hand from their nests. Altogether, it has taken four years and nearly a million dollars to remove 32 golden eagles from the islands. And they’re still not all gone. "You get the dumb ones first and then the smart ones are left. Now we have the smart eagles out there," says Coonan.
For the foxes, even a few golden eagles are too many. Currently, there are as many as ten golden eagles on Santa Cruz Island. In late 2003 the NPS released nine captive-bred foxes on the island and in early 2004 five were dead, apparently killed by eagles.
Moreover, golden eagles are also nesting on Santa Rosa Island, where a breeding pair has recently been discovered. Just as there is a link between eagles and pigs on Santa Cruz Island, there is a link between eagles and mule deer on Santa Rosa Island. Mule deer (Odocoileus hemionus californicus) are not native to the Channel Islands, and golden eagles on Santa Rosa are artificially sustained by preying on fawns in the spring and deer carcasses after the winter cull.
To keep the remaining golden eagles from killing off the rest of the foxes in the wild, some biologists advocate killing the eagles that cannot be caught and relocated. "Lethal removal of golden eagles needs to be a management option. Eagle removal, and fox recovery, will likely fail without it," says the 2003 report of the Island Fox Conservation Working Group, an advisory group of experts that was convened by the NPS in 1999 and that includes National Zoo zoologist Katherine Ralls. This recommendation is echoed by IUCN’s Canid Specialist Group. "We advise, in the strongest terms, that permission be sought to remove golden eagles from the northern Channel Islands by lethal means," say David Macdonald and Claudio Sillero, the chair and deputy chair of the group.
But what is clear biologically is not always clear politically. Killing golden eagles would require a permit from the USFWS, which is reluctant to use lethal control. "Golden eagles are not an endangered species but they are protected and are highly valued in the eyes of the public," says Paul Henson, Assistant Manager of the USFWS' California-Nevada Operations Office in Sacramento, California. "If we consider lethal control it will be absolutely the last resort."
The law does allow for killing golden eagles under certain circumstances, such as to protect livestock or wildlife. "Although the Bald and Golden Eagle Protection Act does authorize take of depredating eagles for purposes of protecting wildlife—as well as livestock—the Service has not granted any authorization for lethal take of eagles in at least 25 years," says Eliza Savage of the USFWS Branch of Bird Conservation in Arlington, Virginia.
One reason is that killing any animals, let alone a national symbol like the golden eagle, can face strong opposition. In fact, in 2002 the Fund for Animals sued the NPS over lethally removing non-native black rats from Anacapa Island, a small Channel Island where the foxes don't live. "Agencies need strong support to go down the lethal removal route," says the NPS’ Coonan.
The next step is to exhaust all the possibilities for capturing the remaining golden eagles, he says. These include using different baits; rigging nets over nests in hopes of catching females when they come to sit on their eggs and feed their young; and trying rocket nets, which are bigger than bow nets but are so loud that golden eagles will probably learn to avoid them. "If all this fails, then we'll have to look at other options," says Coonan.
David Garcelon of the Institute for Wildlife Studies, which has done fox-related work on all the islands, is hopeful. "They're coming to the realization that the golden eagle problem is not going away and that they're going to have to make one hard choice or another," he says.
Besides getting rid of the golden eagles that are on the islands now, the NPS needs to keep others from coming in the future. One way to deter the eagles is to remove the introduced prey they depend on, and the NPS and The Nature Conservancy plan to start removing the estimated 5,000 feral pigs from Santa Cruz Island. Similarly, Santa Rosa Island could be made less hospitable to golden eagles by removing mule deer carcasses after they are culled.
Another way to deter golden eagles is to re-establish the bald eagles that once bred on the northern Channel Islands. Bald eagles (Haliaeetus leucocephalus) are not a threat to island foxes because they eat mostly fish. Biologists believe that bald eagles probably kept golden eagles from colonizing the islands because they defend their territories aggressively against other birds of prey. However, the island’s bald eagles died out in the 1950s, when the toxicant DDT was being dumped off the southern California coast by a Montrose Chemical Corporation manufacturing plant.
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| A pair of foxes in the captive breeding program. (Don Jones/NPS) |
The plant dumped about 1,800 tons of DDT in the ocean between 1947 and 1971, making it the largest known DDT contamination site in the world. In 2000, a lawsuit against Montrose Chemical Corporation and three other companies associated with the DDT plant yielded a $73 million settlement, $30 million of which was earmarked for restoring natural resources in the contaminated region. This restoration includes reintroducing bald eagles to the northern Channel Islands, and so far 15 young bald eagles are living there. If all goes well, these bald eagles will be establishing breeding territories—and defending them against golden eagles—in a few years.
Captive Breeding
But the island fox can't wait for long. The captive
populations are small and could be easily wiped out
by disease or fire, which is a major threat on the islands.
To help buy time for the island fox, the National Zoo
and several other zoos may start captive breeding programs
for the four subspecies with the smallest populations
(those on the three northern Channel Islands as well
as Santa Catalina Island). "The Channel Island
fox seems like an excellent species for a zoo recovery
effort," says Devra Kleiman, the National Zoo’s
former assistant director for research, who is facilitating
this undertaking. "The island fox story is unbelievably
complicated but a wonderful example of just about everything
you need to overcome in a conservation effort."
Federal Listing
In 2000, the four fox subspecies on the northern Channel
Islands and on Santa Catalina Island were petitioned
to be federally listed as endangered. The two subspecies
on the Navy islands were not petitioned for listing
because while their long-term future is uncertain, they
are doing comparatively well right now. In March 2004,
the four petitioned subspecies were finally federally
listed as endangered.
But the foxes' endangered listing is not expected to add legal weight to the already strong biological case for lethal control of golden eagles on the Channel Islands. "There is nothing in federal endangered species law on conflicting protections," says New Mexico State University's Roemer.
The National Academy of Sciences (NAS) does, however, provide guidance on how to handle conflicts between protected species, which is important because such conflicts are on the rise as habitat dwindles. According to its 1995 report, "Science and the Endangered Species Act," resolving such conflicts should include considering which species is most likely to suffer irreversible harm if its needs are not fully addressed, and considering which species is more important to the ecosystem in question. Under these guidelines, the island fox would be the top conservation priority, because it is native to and found only on the Channel Islands, while the golden eagle lives throughout the northern hemisphere and is not native to the Channel Islands. The National Zoo’s Ralls served on the NAS committee that created this report.
Legal weight or not, the endangered listing could still benefit the island fox by alerting and educating the public. "It will help our cause," says the NPS' Coonan. "It will help build a coalition of support." Garcelon of the Institute for Wildlife Studies agrees, adding that "the foxes are adorable and the cute factor will help with public support." Without the golden eagles, he predicts that the northern island foxes would rebound quickly because captive-bred foxes thrive when released in the wild on the eagle-free Santa Catalina Island. "They're bulletproof—no natural predators and they eat just about anything," he says.
Now all the island fox needs is for us to do our part.
—Robin Meadows is a contributing editor of ZooGoer. She wrote about wild Pacific salmon in the January/February 2004 issue of the magazine.
ZooGoer 33(4)
2004. Copyright 2004 Friends of the National Zoo.
All rights reserved.
