Endangered Peninsular Bighorn Sheep Population Sees a Rise at Anza Borrego Count

Peninsular bighorn sheep #257 in Anza Borrego | Creative Commons photo by djfrantic

There's some good news for fans of the Peninsular bighorn sheep: the iconic desert critter's numbers seem to be up this year, at least in the environs of Anza Borrego Desert State Park.

The Anza Borrego Foundation's annual bighorn sheep count tallied 329 bighorns in the park over the Fourth of July weekend, well above last year's count of 255.

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Held each year in the heat of summer, the count attracts volunteers from across the country -- about 45 this year -- who sit out in the desert for three days to count sheep, with temperatures reaching 120° in the afternoons.

The Peninsular bighorn sheep, a distinct population segment of the desert bighorn, is listed as endangered under the Endangered Species Act. Fewer than 300 individual sheep survived during the species' low point in 1996, due to threats from predation, human interference, habitat loss and disease from domestic animals. Domestic sheep, cattle, and other livestock carry diseases such as bluetongue, epizootic hemorrhagic disease, and -- most devastatingly -- pneumonia, all of which can devastate bighorn populations.

Peninsular bighorn range from the desert scrub slopes of Mount San Jacinto southward through the Peninsular Ranges into Baja California. While the effect of human activity in the northern edges of their range continues to be of concern to wildlife managers, Anza Borrego -- California's largest state park -- offers a huge core of protected land at the heart of the Peninsular bighorn's range, and it would seem that protected habitat is making a difference.

The count takes place during the hottest part of the summer as that's when the sheep congregate around watering holes, perennial springs and seeps. During more temperate parts of the year the sheep are much harder to find, spread out across the desert landscape. Volunteer sheep-counters are trained to cope with the extreme heat, and some of them spend the three day count camping well away from pavement. The video embedded here gives a glimpse of what it's like, though of course without the heat: for the full effect, you may want to fire up your oven and stand in front of the open door as you watch.

This year's count of 329 sheep -- 84 of them at one spring alone -- will be used by biologists to extrapolate what the total population of Peninsular bighorns might be. Current estimates range at just under a thousand individual sheep, more than a threefold increase from 15 years ago. Aggressive protection measures such as banning off-roaders from spring areas and a captive breeding program are part of the reason for the species' rebounding, as is cooperation by ranchers who have removed domestic animals from parts of the sheep's range.

The rebound is encouraging news indeed. As Anza Borrego Desert State Park's Superintendent emeritus Mark Jorgenson explains in this video, protecting the Peninsular bighorn means protecting the desert itself:

To learn more about the sheep count, contact the Anza Borrego Foundation.

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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