Losing foxes

From ANIMAL PEOPLE, May 1999:

Abruptly extirpating established feral species may help some native species at cost of finishing others.

The unique foxes of San Miguel, Santa Rosa, and Santa Cruz islands, off southern California, offer a case in point. Biologists believe grey foxes reached the islands more than 20,000 years ago. Over time, they became a distinct subspecies, 18% smaller on average than their mainland cousins. They eat mostly mice.

The foxes in the early 1980s were believed to be among the island natives–– chiefly plants– –who were jeopardized by feral sheep, goats, pigs, cattle, horses, burros, deer, and bison, left by 19th centu- ry ranchers and 20th century sport hunters.

Saving the island foxes was one goal of the National Park Service and the Nature Conservancy in purchasing the whole Catalina Island chain, creating Channel Islands National Park, and extirpating hooved animals in a multi-million-dollar 20- year putsch .

The Park Service began counting island foxes in 1993. There were then 3,500 of them. The San Miguel colony peaked in 1994 at 450. Feral eradication was going full blast– –shotgun blast. The head bio- xenophobes congratulated themselves that it was working: the foxes would survive.

But maybe the foxes just boomed to an unsustainable population level by shift- ing from their mouse diet to feast on carrion.

Next came a crash. San Miguel had 300 foxes in 1995, 100 in 1996, 70 in 1997, 40 in 1998, and just six this year. Together, the islands now have barely 400.

Park Service biologists in early April 1999 announced that they had found the cause: four radio-collared foxes on San Miguel were eaten by golden eagles. “The Park Service is considering trapping the eagles and transporting them to the mainland, since they are not native to the islands,” said an official bulletin. But to fly the 25 miles between the islands and the mainland is easy for an eagle, if the islands still attract them. Eagles are drawn to either abun- dant carrion or small prey––like mice, or island foxes, who are just big enough to make a meal for a whole nest of young.

Eagles may have migrated to the Channel Islands long ago to feed on carrion left by hunters and ranchers. But they were shot as potential sheep predators, and repro- ductively inhibited by cumulative absorption of the insecticide DDT.

Eagle protection and recovery, following the 1973 federal ban on DDT, coincided with the beginning of the purge of hooved stock from the islands. The stench of the remains of hooved animals shot by the tens of thousands was veritable eagle bait.

Now, however, with the feral eradication nearly over, the artificially cre- ated Channel Islands niche for carrion-eaters is declining. Hungry eagles, accustomed for 20 years to finding food on the islands, turned to hunting foxes––and that may be the end of the foxes, doomed by the carnage that was supposed to save them.

particular nations, Australia would probably rank among the top five in each category.

Among recent finds are the first marsupial mole ever seen alive; the false king brown snake, believed to be highly ven- omous; a spiny beetle of Jurassic origin, identified in September 1998 from living specimens found in 1991 and 1995; a giant dragonfly, also of Jurassic origin, seen alive for the first time in seven years during January 1998; five species of freshwater crab found in Sydney pet shops by Shane Ahyong of the Australian Museum; a giant predatory prawn of Jurassic vintage, with the most advanced vision of any invertebrate, found alive by Ahyong in Sydney harbor; and a

However, eight individuals of a previously unknown subspecies of snipe were photographed in October 1997 on Jacquemart Island, one of the few islands off New Zealand with no history of rat infestation.

Other recent New Zealand finds include the leopard chimaera, an ancient rela- tive of sharks; a deep-sea barnacle found on a volcanic vent by a mixed team of New Zealanders and Canadians who at last report were still squabbling over who would get to name it; a group of 300 unique frogs on Stephens Island in the Marlborough Strait; and a black-eyed gecko in an area geological- ly isolated from the only other known black- eyed geckos for the past million years.

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