|From The San Francisco Chronicle
ANIMAL ATTACK FILES
Cougars Wiping Out Sierra Bighorn Sheep, Scientists
Mountain lions may be pushing endangered Sierra Nevada bighorn sheep to extinction, and wildlife biologists say they are unable to do anything about it.
The scientists maintain that a simple solution to the problem exists but that it cannot be carried out because of the growing trend of crafting public policy -- including wildlife policy -- at the ballot box.
Cougars were given sweeping protection in a 1990 state ballot initiative after widespread popular concern about the stability of their population. The big cats multiplied dramatically, and they began gobbling up the bighorns with a vengeance.
Wildlife biologists would like to eliminate a few of the most voracious cats to give the sheep a little breathing room. But the 1990 initiative allows cougars to be killed only if they threaten people, pets or livestock. Endangered species are not covered in the exemption.
And to the frustration of the scientists, supporters of the big cats are fighting any moves to change that part of the law. ``They have no vision of conservation,'' said bighorn expert John Wehausen, a biologist with the University of California's White Mountain Research Station, in criticism of the Mountain Lion Foundation, his primary opponent on the issue.
``They're an animal rights group, not an environmental group,'' said Wehausen. ``We (wildlife biologists) are concerned with habitat preservation and maintaining rich biodiversity, but they're concerned with the life of a particular animal in a particular place. They essentially reject science.''
Lynn Sadler, the executive director of the Mountain Lion Foundation, countered that the link between mountain lion predation and bighorn declines has not been adequately demonstrated.
``Predators eat endangered species all the time,'' she said. ``It's what they were put on this planet to do. Not far from here, great horned owls are eating endangered Swainson's hawks.''
Mountain lions do eat some bighorns, Sadler acknowledges, ``but it has never been proven that eliminating lions will take care of the bigger problems bighorns are facing.''
Sadler said Sierra Nevada bighorn sheep live in a harsh alpine environment that makes survival problematic under any circumstance.
Besides, said Sadler, killing sheep-eating lions would probably do little good because the cats have a highly developed sense of territory.
``When one lion is removed, another moves in,'' she said. ``Younger mountain lions are always waiting for the opportunity to exploit territory controlled by an older animal.''
Until the past few years, Sierra Nevada bighorn sheep -- cousins of the more numerous desert bighorn -- were staging an impressive comeback after dancing on the brink of extinction for almost a century.
Although they had once ranged across the spine of the Sierra, these magnificent animals had been reduced to a few isolated herds by 1900.
Disease and overhunting were the primary culprits. Bighorns are exceedingly susceptible to domestic sheep maladies, and bighorn meat was considered so succulent and delicious that it was featured on the menus of restaurants in Bodie, now a deserted mining town on the eastern slope of the Sierra.
By the late 1970s, only about 250 sheep were left. They lived in two herds in the central Sierra, one on Mount Baxter and another on Mount Williamson. In 1986, biologists began transplanting animals from the Baxter herd to Lee Vining Canyon, just outside Yosemite National Park.
The animals thrived, and other transplants followed, to both the Lee Vining Canyon area and Mount Langley in the southern Sierra. By 1991, the Sierra Nevada bighorn population stood at about 400 animals and was expanding rapidly.
``It was fantastic,'' recalled Wehausen, a lean, gangly man with a spare ginger-colored beard. ``The herds were growing at 24 percent a year -- that's a remarkable rate.''
But that began to change, biologists say, with the passage of Proposition 117 in 1990.
The state's cougar population climbed quickly after the measure was approved and is now estimated at 5,000 animals. Within two years of the initiative's passage, biologists began to note a dramatic increase in the number of sheep killed by lions.
Further, researchers say, the lions were changing the bighorn's behavior in a way that was anything but healthy for the bighorns.
``We always knew that lions killed sheep,'' said Leslie Chow, a biologist with the U.S. Geological Service who studies cougars in Yosemite National Park through a grant from the Yosemite Fund.
``But as the '90s went on, we saw more and more predation from lions,'' said Chow, ``especially during the winter, when the sheep are stressed from the weather and lack of food.''
And the problems were compounded when the sheep retreated to higher altitudes to escape the lions.
``It got to the point that the sheep stopped going down to the lower terrain where the winter feed was good,'' Chow said. ``Instead, they wintered out higher up.''
And the higher the range, the less forage there is during the brutal Sierra winter, Chow said. Sheep emerge from the snowy months in poor condition, making them particularly vulnerable to disease, parasites and predators.
``They also have fewer lambs, since breeding success is pegged to good winter nutrition,'' said Chow.
Wehausen said Sierra Nevada bighorns are about to become extinct, and the only hope for their salvation is a captive breeding program similar in scope to the one undertaken for the California condor.
``It's not a matter of maybe,'' he said. ``We're at the crisis point right now. There are fewer than 100 Sierra Nevada bighorns left
--that's totaling all the herds. Somehow, we have to come up with funding by this winter so we can start capturing some of the animals.''
Such a solution is hardly ideal, said Wehausen. Bighorns breed readily in captivity but they lose many of their natural instincts when penned, making them easy pickings for predators when and if they are re-introduced to the wild.
Great care must also be taken with the breeding program to ensure that the offspring are not excessively inbred, Wehausen said.
``These are incredibly valuable genes,'' said Wehausen, ``and it would be tragically easy to lose them.''
The biologists say there is a far better and simpler solution to the problem than captive breeding -- selective control of the cougars.
Chow thinks that mountain lion populations are at an all-time high in California, exceeding the numbers that existed in the centuries before European contact. In those days, grizzly bears may have kept cougars in check, Chow said. Grizzlies are now extinct in California.
``It's not as though the situation now is `natural,' '' Chow said. ``California's wild ecosystems have been dramatically manipulated for centuries. There's compelling evidence that a lion population of this density is quite unusual.''
Lions are highly individualistic animals, said Chow, and quickly develop specific tastes when it comes to prey.
``As a species, they heavily favor deer,'' he said. ``But some get particularly adept at taking other prey -- bighorns, for example. When we could still legally take lions, we found that removing one or two problem animals from bighorn range greatly reduced (sheep) mortality.''
The California Department of Fish and Game concurs with that view and supported a bill introduced in the state Assembly last year that would have allowed a limited take of lions in the Sierra under a special research program.
``It was apparent to us that a few lions -- or even one lion -- could have a devastating effect on the remaining Sierra Nevada bighorns,'' said Steve Torres, a Fish and Game biologist in charge of the agency's bighorn sheep programs.
``All the rules of predator/prey relations don't really apply when the prey is in danger of extinction,'' said Torres. ``In any wildlife management scenario, the predator should not eliminate the prey.''
But the legislation promptly died when the Mountain Lion Foundation indicated its opposition.
``Under Proposition 117, (killing lions) is strictly against the law,'' said Sadler. ``We're not opposed to studying possible solutions to the bighorn problem, nor are we opposed to relocating problem lions. But the people of California have made it plain that they don't want to see mountain lions hunted and killed.''
Besides, said Sadler, she is by no means comfortable with Fish and Game's evaluation of the problem.
``Fish and Game's science has proved highly suspect in the past, and I believe that could certainly be the case here,'' she said. ``The bighorn's problems didn't start with mountain lions, and they don't end with them. Overhunting, domestic livestock diseases and habitat loss are far more pressing problems.''
Yet Torres reiterates that the crisis facing the Sierra Nevada bighorn demands immediate action and says the sheep's plight points to a larger issue. Increasingly, he said, wildlife policy is determined by voters rather than biologists.
``More and more, the (initiative process) is controlling the way we manage our wildlife,'' Torres said, ``with sentiment and emotion often counting for more than science. You end up with these broad- brush approaches that don't allow biologists the flexibility they need to address regional problems.''
©1998 San Francisco Chronicle
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