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Pneumonia Outbreak Prompts Tracking of Mojave Preserve Bighorn Sheep

Bighorn sheep near the Old Dad Mountains | Photo: kschneider/Flickr/Creative Commons License

Wildlife biologists will be putting radio collars on the Mojave National Preserve's bighorn sheep in early November to try and learn more about an outbreak of pneumonia that has killed more than a hundred animals.

Biologists from the National Park Service and the California Department of Fish and Wildlife (CDFW) will be flying over the Preserve's mountain ranges for four days starting November 3 to capture, examine, and collar bighorn sheep in an attempt to track the spread of the usually fatal respiratory disease. Tracking the animals' movements through the desert will give wildlife managers a better chance of finding ways to limit the disease's impact on the desert bighorn population.

Mojave National Preserve scientists suspect that the outbreak may have begun when sick domestic sheep were illegally dumped in the Preserve. Domestic sheep and goats are carriers for the disease, which does not occur naturally in desert bighorn sheep populations.

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There seem to have been two distinct outbreaks of pneumonia in and near the Preserve since the first dead animals were found this summer, lending credence to the notion that multiple instances of sheep dumping are behind the problem. Wildlife biologists will survey mountains ranges just outside of the known outbreak centers by helicopter; any bighorn sheep they encounter will be netted, enabling crews to take nasal swab samples and affix GPS tracking collars provided by CDFW.

The data from the collars will allow scientists to track the spread of the disease through as-yet uninfected herds.

"The idea here is to have collared animals in the surrounding mountain ranges so we can have an early warning of the spread of the pathogen," Preserve science advisor Debra Hughson told the Riverside Press-Enterprise. "We can get a better understanding of the progression of the disease, its spread and impact on herds."

The outbreak of pneumonia was first noted in May in bighorns in the Old Dad Mountains, with a subsequent outbreak in the Marble Mountains south of the Preserve. Preserve rangers have also found domestic sheep carcasses at Halloran Summit in the northern regions of the Preserve, and pellets from domestic sheep at Foshay Pass near the Providence Mountains. Given that Foshay Pass is accessible only by a rugged dirt road, it's unlikely that truckers with livestock would be there unless they intended to dump sick or dead animals illegally.

Though at least a hundred bighorn have died of pneumonia in and near the Mojave National Preserve since the outbreak began, CDFW is still planning to hold this year's desert bighorn hunting season in the area. The Peninsular Ranges population of desert bighorn is listed as endangered under the U.S. Endangered Species Act, but the Mojave National Preserve's bighorn enjoy no such protection. Opening Day is December 1.

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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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