RIVERSIDE — Hoping to help the imperiled desert tortoise by controlling one of its major predators, the U.S. Bureau of Land Management plans to kill up to 750 ravens annually in the California desert.
Under a permit from the U.S. Fish and Wildlife Service, the BLM later this year intends to begin poisoning and shooting ravens in areas where their attacks on young tortoises have exceeded normal levels.
The goal of the program is "not to exterminate the raven but to reduce its numbers to the point where young tortoises have an opportunity to reach maturity and breed," Gerald Hillier, the BLM's desert district director, said Tuesday.
Hillier said the desert's raven population has increased by 1,500% over the last 20 years, largely because of the proliferation of trash dumps, sewage ponds and other artificial food sources. Juvenile tortoises, whose shells are as thin as human fingernails, have become one of the bird's favorite meals.
The announcement drew applause Tuesday from tortoise lovers, who called it a vital part of a broad-based campaign to rescue the reptile--which was added to the nation's list of threatened species in March--from the brink of extinction.
But the Humane Society of the United States, which challenged a pilot raven control program conducted by the BLM last year, expressed skepticism about the number of birds the federal agency intends to kill.
"Our problem with the BLM in the past was they wanted to kill excessive numbers of ravens in areas where it was not demonstrated that such a slaughter would do any good," said John Grandy, the Humane Society's vice president of wildlife in Washington. "We realize the tortoise needs emergency help, but ravens need to eat too."
Grandy also called the BLM's plans to use Starlicide, an avian poison, unwise and cruel. He said it can take two days for ravens to die after ingesting the poison and noted that it can be toxic to other wildlife.
Last year, the Humane Society sued the BLM after the agency announced plans to kill 1,500 ravens in Twentynine Palms and the Desert Tortoise Natural Area preserve near California City. In a pretrial settlement, the BLM agreed to kill just 56 birds and avoid the use of poison where possible.
Further research, however, along with the subsequent listing of the tortoise as a threatened species, have underscored the need to control the mushrooming flocks of ravens, the BLM has concluded. In some areas of the western Mojave Desert, federal biologists say, 85% of juvenile tortoise deaths are attributable to ravens.
Ravens are only one culprit nudging the tortoise, California's official state reptile, toward extinction. The slow-moving animals--whose numbers have declined by as much as 50% over the last decade in some parts of the desert--are also falling victim to a mysterious respiratory disease, off-road vehicles and destruction of habitat.
In addition to shooting and poisoning hundreds of ravens over an indefinite period, the BLM plans a long-range program that includes raven sterilization, conditioned "taste aversion," trapping and installation of anti-perch devices throughout the desert. The BLM predicted that it could reduce the rate at which the tortoises are killed by 50% to 70%.