Anza-Borrego's Desert Bighorn Sheep
Last Refuge of the Bighorn
3-Part Series Part 1
By Mark Jorgensen
Anza-Borrego is one of the last refuges of the Peninsular Bighorn Sheep. Only 280 of this subspecies remain in the United States and 200 find refuge in the park. Anza-Borrego is important to the Bighorn when you consider the explosive metropolitan growth of Southern California.
The park has an ongoing program to help the bighorn. Over a quarter of million dollars has been spent to improve bighorn habitat. Projects include construction of six water sources in the Vallecito Mountains, fencing of the park boundary to exclude trespassing cattle, the live removal of wild cattle from many of the west side canyons, and removal of exotic trees from desert water holes.
The Desert Bighorn has lived in the Borrego Desert for thousands of years. Bighorn migrated from Siberia over 10,000 years ago, extending their range throughout western North America. Today, Bighorn still range into Baja California, but their numbers have dwindled to less than three percent of the estimated 1.5 million of the early 1 800s. Human activities are responsible for the Bighorn's decline. Grazing, mining, depletion of water holes, homesteading, and use as camp meat spelled disaster for the Bighorn. Today their future rests in our hands. We can help them survive or let them dwindle into history. Hopefully, human concern will help in making their future look brighter.
Visiting the park in fall, you may be fortunate to find Bighorn close to campgrounds and roadways This is the mating period when the large rams, carrying their huge horns proudly, seek out the ewes. The animals may appear bold at this time, making you wonder about their reputation for being wary and hard to see. Sheep have recently been seen in the middle of the road on Yaqui Pass and bedded down within 50 feet of Montezuma Grade. It seems the mating season is a time when Bighorn worry less about humans and predators and more about finding a mate.
Lambs are born six months after mating occurs. Most are born near steep cliffs from late February to May. Only about one-third will survive their first summer. An animal born late in the season stands little chance of survival, since temperatures reach over 100 degrees F in May and often reach 120 F by June. Recent studies of high lamb death rates focus on viruses possibly introduced by domestic livestock, to which the native Bighorn have little or no immunity. Studies continue, and the park has done everything possible to remove feral livestock and to keep Bighorn habitat free of trespassing cattle and goats.
Ewes are protective of their young for many months. Yearlings, often abandoned while the ewe is giving birth to her next lamb, may be seen again with the ewe and lamb late in the spring. Bighorn find safety in numbers and are ever watchful for predators such as Coyotes and Mountain Lions. In a recent three-year period, Mountain Lions were documented taking over 40 radio-collared Bighorn Sheep in Anza-Borrego. Ewe horns are about ten to fifteen inches long and their sharp tips are effective protection against Coyotes.
When a lamb is sick and pneumonia renders it helpless, Coyotes become superb predators. The ewe must abandon the lamb and head for the steep slopes and safety. All too often researchers or hikers find the carcass of a dead lamb near a water hole.
To maintain a sheep population, about 25% of the season's lambs should survive. The Vallecito group has maintained a population of about 30. The Coyote Canyon group is declining due to Mountain Lions. The Palm/ Tubb, and the Southern Santa Rosa groups seem to be holding, with the loss of a few to Mountain Lions.
An alarming decline has been occurring in the southern end of the park. In Carrizo Gorge, we have documented a drop from about 120 sheep in 1972 to less that 40. Off-road vehicles, trespassing cattle, poaching in the 1960s and early '70s, drought, disease and Mountain Lion predation have worked together to push this population to the edge. We hope we can save this group before it is too late.
The "Borrego Cimarron" (as it was called by Spanish explorers) lent its name to this park, and we are dedicated to providing a lasting refuge for its future. These are challenging times in the recovery of Desert Bighorn in California. The future of the Bighorn is in our hands and with your help we're proud to say we're doing something about it.
Where to find them. Bighorn Sheep Watching
Text: Copyright Anza-Borrego Desert State Park
Photographs and HTML: Copyright DesertUSA.com
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