Deaths of Five Bighorn Sheep Concern Experts

Five endangered peninsular bighorn sheep have died in the mountains near Palm Springs since late last month, alarming conservationists who have struggled for decades to rebuild the species’ fragile population.

The young adult sheep appeared healthy just days before three unexpectedly died from bacterial pneumonia, and two from undetermined causes, said Jim DeForge, executive director of the Bighorn Institute, a Palm Desert nonprofit organization that keeps track of the animals.

“To lose them so quickly is a concern,” DeForge said.

Assaulted by viruses carried by domestic animals, by human encroachment and air pollution, among other factors, the peninsular bighorn population dipped from 1,200 in the late 1970s to a low of 280 in 1996. For a period in the 1980s, 90% of bighorn lambs died, DeForge said.

Since then, conservationists have fought to preserve the sheep’s shrinking territory and fortify their ranks. Peninsular bighorns were listed as federally endangered in 1998.

“We are certainly concerned about the deaths of these five adult sheep,” said Jane Hendron, a spokeswoman with the U.S. Fish and Wildlife Service. But “it is far too early to determine if this is an isolated series of deaths or if this is part of potentially a more serious issue.”

The roughly 700 peninsular bighorns in the United States live between Palm Springs and Baja California, favoring territory below 4,000-foot altitudes. The dead sheep were found in the San Jacinto and Santa Rosa mountains, west and south of the Coachella Valley in Riverside County.

The pneumonia that killed three could be an indicator of contaminants in the environment. “We’re not ruling anything out,” DeForge said.

The Bighorn Institute, which has about 30 bighorn sheep tagged with radio collars, is monitoring several animals that have lost weight and appear undernourished.

“I think the big question is: Can the sheep take a big hit” and survive as a species, said Joan Taylor, conservation chairwoman of the Sierra Club’s eastern Riverside County group.

Samples from four carcasses are being analyzed by state laboratories; the fifth was too decomposed to yield usable information, DeForge said. Conservation and federal agencies and the state Department of Fish and Game are sharing information and intensifying monitoring.

“This disease, caused by some kind of environmental contaminant, put together with the threat of loss of protected habitat would keep the species endangered for a long time,” said Daniel Patterson, a desert ecologist with the Center for Biological Diversity, a conservation group with offices in Joshua Tree.