Kristin Scharkey and Janet Wilson | Palm Springs Desert Sun

The Desert Sun

At least 20 desert bighorn sheep have died in a San Gorgonio mountain population in Southern California, 100 miles east of Los Angeles. The cause of death? Pneumonia, most likely from domestic sheep or goats, though wildlife specialists are examining other possible causes, including pathogens from feral cattle to the west and disease from a different bighorn group to the south.

“Since the beginning of December, I have recovered 20 dead sheep, and I suspect that’s just a portion of what’s occurring,” said Jeffrey Villepique, a wildlife biologist with the California Dept. of Fish and Wildlife inland deserts region who is leading the probe into the deaths.

A known herd of about 200 of the sheep has long lived and grazed in the area, from Mission Creek and Whitewater Canyon up miles of rugged slope to the peak of Mt. San Gorgonio. Villepique and a fellow biologist have been hiking across the hills for the past several weeks, and have seen less than a third of the numbers of live sheep they would expect.

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“All it takes is this disease introduction event to potentially wreak havoc on healthy populations,” he said. Notably, all ages are dying, from large rams to lambs. Groups of dead sheep have been found together – while shy of humans and wary of predators, bighorns are extremely gregarious with each other, rubbing noses and foraging on the same grasses. That means the disease can spread rapidly.

Lilly Lawson/Special to The Desert Sun

“It’s really tragic,” said Jack Thompson, regional director for The Wildlands Conservancy, a nonprofit that manages Whitewater Preserve, near where many of the dead sheep have been found. “The bighorn sheep are such an iconic species for the California desert.”

Thompson said the chance to see “a really amazing animal” is part of what draws visitors to the area. “They have an encounter with it,” he said.” So seeing them die, personally, is really, really sad.”

'There's obviously something going on here'

Thompson said his staff started seeing suspect dead sheep in November. The first was found roadside on Nov. 15, just north of the unincorporated community of Bonnie Bell. On Nov. 28, another dead ram was reported in a riverbed in the same area. That day, rangers also encountered a live bighorn “acting loopy” just north of the community.

“It was walking in a fashion where it obviously seemed like it was having some kind of trouble,” Thompson explained. “It was confused and should have been more disturbed by the presence of people. That was the first time we saw one that we said, ‘There’s obviously something going on here. This is a sick animal.’”

Kyle Christensen/Special to The Desert Sun

Villepique said he heard reports of dead sheep in November from a UC Riverside graduate student and the conservancy, but at first chalked up one death to normal predation, possibly by a mountain lion, and the second to a collision with a car.

But when he heard a report of a large male that had been standing by the side of the road for 24 hours straight, he thought, “Uh oh,” and decided it was time to investigate.

“It was clear this animal appeared to be ill,” he recalled, with its snout pointed downward and its ears sagging. Also odd was that a 5-year-old ram would let a ranger get within 30 feet and tranquilize him with a dart.

Once the animal was immobilized, a trained wildlife veterinarian determined it was in extremely poor shape. It was euthanized and immediately shipped to a special facility at UC Davis, the California Animal Health and Food Safety laboratory, where wildlife pathologists have been trying to crack the riddle of what killed the ram and nearly two dozen more sheep from the same population.

“The initial evaluation is this ram had pneumonia, which is just another way of saying a whole bunch of fluid in the lungs,” said Villepique. “We’ve been trying to identify the pathogen or pathogens responsible for that pneumonia, and we’re still working to try to identify the source of the pathogen.”

Since then, state biologists, rangers and area volunteers have found increasing numbers of sick and dead animals. Many were emaciated and coughing badly. Samples were taken from the animals and shipped to the Davis research lab “to try to tease out which pathogen or multiple pathogens are causing this,” said Villepique.

In total, four dead sheep were found by or reported to Whitewater Preserve rangers in early December.

On Dec. 27, the remains of seven young males or ewes were found by Whitewater Preserve rangers on the east side of the canyon, after reports from hikers. “You’ll find groups that together have walked to a point and all are obviously infected by the same thing, and they all just sit down and die together,” said Thompson.

On Jan. 10, two more bighorn were reported dead east of Bonnie Bell.

Villepique has recovered all those animals and seven more.

He hopes subgroups of the San Gorgonio population have headed for higher elevations and will survive unscathed.

Cause remains unknown

The cause has been roughly narrowed to three possibilities: bacteria carried by domestic goats, possibly owned by a Morongo Valley resident who let them loose to graze on the public lands; disease carried by bighorn sheep in the Peninsular range across Interstate 10 to the south of the affected population; or pathogens carried by the feral cattle that roam Whitewater Canyon and surrounding land.

Pneumonia has devastated bighorn sheep since Spanish missionaries explored the West, with outbreaks as far north as Oregon and Washington and as far south as Mexico. Recent research shows up to 90 percent of the outbreaks are caused by interaction with domestic livestock, usually sheep grazing the same public lands, but occasionally goats. “That's the prime suspect here,” said Villepique.

But he and the other researchers are keenly interested in whether the wild cattle or other bighorn herds could be the culprits. Interstate 10 normally acts as a barrier separating the Nelson’s and the Peninsular populations, but particularly during mating season, males will “go on a walkabout.” There have been records of bighorn finding their way under the interstate to the other side. So far, only one of 11 samples has showed a pathogen that might come from sheep in the Peninsular range.

Jack Thompson/Special to The Desert Sun

Cattle are another major concern. Thompson, who hikes the area frequently, estimates there are 60 to 80 feral bulls, cows and calves in Whitewater Canyon, and at least 100 in the region.

“My guess is directly in (the sheep’s) pathway (in the canyon) … there’s probably a consistent 20 to 30 (cattle) they’re going to be crossing paths with,” said Thompson.

“This has been a great fear of many that, over time, the sheep would contract disease from the cattle and that this kind of thing would happen,” Thompson added. “Even though, at the moment, we don’t know what is indeed the cause, just the fact that it is possible is very disturbing,” he said.

The die-off has also coincided with a partial government shutdown, which Thompson said is “terrible timing.”

Thompson said federal agencies secured funds to remove the cattle before the start of the die-off, after feral dogs began preying on the herd. The cattle also began charging visitors in the Sand to Snow National Monument.

He also said funds were allocated for studies, fencing to protect certain areas, and cattle removal. But before the government shutdown, Thompson was told the funding was “unavailable" and has since been unable to get clarity.

“We need, as fast as possible, to get the science out to determine whether or not the cattle are the culprits,” Thompson said.

Villepique said contact had been made with an area biologist who was possibly going to do a round-up to “squeeze” the cattle through narrow chutes, then tranquilize them and obtain samples of mucus from sinus areas to be sent for analysis.

The dying animals are Nelson’s bighorn sheep, named for a British explorer and naturalist who identified many species in the West in the late 1800s. They roam patches of habitat from the White Mountains south to San Bernardino range, then southeast to Mexico. A subset population, dubbed the Peninsular bighorn sheep, was declared federally endangered, while the entire desert bighorn species is considered a sensitive species in California, and is protected under state law.

Hunting in the 1800s and early 1900s and fragmentation of habitat by development in the latter 20th Century sent their numbers plummeting, as did outbreaks of disease, particularly after prolonged drought or other stressors. Many populations have rebounded, but a chance interaction with a domestic animal can cause a major die-off. There is no known risk to people from the sheep pneumonia. Humans are the risk to the sheep.

“I hope this conveys the vulnerability of these majestic animals, that we as people need to do our best to keep them from the threats,” said Villepique. “It’s a reminder of the need for ongoing vigilance.”

Kristin Scharkey is the editor of DESERT magazine and community content editor at The Desert Sun. Reach her at kristin.scharkey@desertsun.com or on Twitter @kscharkey. Janet Wilson is The Desert Sun’s senior environment and investigations reporter. Reach her at janet.wilson@desertsun.com or on Twitter @janetwilson66.

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Peninsular bighorn sheep in the desert