Not far from the tranquil, impossibly green fairways of Palm Springs, as golfers sink their putts to the sound of ice tinkling in frosted glasses, a fight rages in the harsh, rugged mountains to the south.
In one corner, we have a population of bighorn sheep unique to California, known as the Peninsular bighorn, magnificent in their signature helmet of curled horns. In the other corner, we have the darling of animal rights' groups and conservationists alike - the mountain lion. In the middle are wildlife managers and biologists. The arena consists of 7 mountain ranges stretching from Palm Springs to Mexico, a rock and brush covered landscape that includes the 600,000 acre Anza-Borrego Desert State Park.
The Peninsular bighorn has just been listed as a Federal Endangered population. The reason is a decline in numbers over the last 20 or so years, estimated from annual counts at waterholes, along with more recent helicopter surveys. In 1979, for example, about 1180 bighorns roamed the stark ridges and slopes of these mountains, whereas in 1998, the animals numbered less than 300.
Professor Walter Boyce and ecology graduate student, Esther Rubin, along with their colleagues in the School of Veterinary Medicine at UC Davis, have been investigating the decline of the Peninsular bighorn in collaboration with ecologists and managers from the California Department of Fish and Game and other wildlife agencies. In addition to calculating changes in population size, Boyce and his team began a study in 1992 to examine the lives of the bighorns in greater detail.
To do this, the researchers had to put radio collars on over 100 adult sheep, a difficult, but thrilling job that involves a helicopter, a capture net and a blindfold to calm the animal. The whole process takes little more than 30 minutes, after which the bighorn runs off, none the worse for wear.
The radio collars enable scientists to locate and track the animals, and observe their behavior: what they eat, who they hang out with, when they give birth, what they die of. The UCD study turned up some surprising findings.
Ecologists have blamed the decline of this bighorn population on a variety of factors, including disease, drought, and habitat destruction. During the five years of this study, however, Boyce and his colleagues found that mountain lions were the biggest cause of mortality.
Over 40 of the adult sheep that were radio collared ended up a meal for a mountain lion, and the predators accounted for over 65% of all documented bighorn deaths. The lions don't appear to be fussy: they'll kill lambs, ewes, and even 200 - pound rams equipped with 40 pounds of curved horns.
Although this level of lion predation might be the norm for larger populations of bighorns in other areas, the endangered Penninsula bighorn might not be able to withstand it. So what's the solution?
Some managers think that culling the lions is the most efficient course of action, but one that would meet fierce resistance. Since 1972, Californians have repeatedly voted in measures that ensured the mountain lion's protection.
Whatever decisions are made to solve the lion-bighorn problem, should be guided by research that brings to us an objective understanding of the animals' themselves.
Questions concerning lions as well as bighorns are relevant. How many cats are doing the killing? Are these transient lions just grabbing a meal as they pass through, or established residents? Holly Ernest, a graduate student working with Professor Boyce is trying to identify the lions making kills by examining mountain lion DNA, obtained through feces, and saliva from bite marks on carcasses. Preliminary results suggest that during the five years of the study, as many as eight different lions have killed bighorn sheep in this area.
In the end, a coalition of wildlife agencies, using the findings
from research such as that being done at UCD, will have to decide
the best way to manage the two species so that both survive in
the region. In the meantime, wildlife managers are working to
minimize the other threats to the Peninsular bighorn sheep that
have in the past been more serious than lion predation. These
include disease, drought, and, most serious of all, those golf
courses and developments that creep inexorably into bighorn habitat.
Dept. of Anthropology, University of California, Davis, CA 95616.
e-mail: kjstewart@ucdavis.edu