Last Refuge of the Bighorn
By Mark Jorgensen, State Resource Ecologist
California State Parks ©2000

Anza-Borrego Desert State Park® is one of the last refuges of the Peninsular bighorn sheep. Only 335 of this population remain in the United States and 215 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 a million dollars have been spent to improve bighorn habitat. Park Staff and Volunteers have constructed six water sources in the Vallecito Mountains. We have fenced segments of the Park boundary to exclude trespassing cattle and have removed cattle from many of the west side canyons. Exotic trees are being removed from desert water holes so that they will flow freely once again.

Past and Future

The desert bighorn has lived in the Anza-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 1800s. Human activities are responsible for the bighorns' decline. Grazing, disease, 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 to make their future look brighter.

Life Cycle

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 Yaqui Pass and bedded down within fifty feet of S-22 on the Montzuma Grade, It seems the mating season is a time when bighorn worry less about humans and predators and more about finding a suitable partner.

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 in May and often reach 120 degrees Fahrenheit 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.

Safety in Numbers

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 seven-year period, mountain lions were documented taking just over 60 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 individuals. The Coyote Canyon group is declining due to mountain lions. The Palm Canyon, Tubb Canyon 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 than 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.

You Can See Bighorn

If you would like to see a bighorn sheep in the Park, your best bet is to visit in summer or fall. During this period sheep are forced to come to water and they can be seen in canyon bottoms. From August to December, during the mating season, they are frequently observed. Hiking into the back country is often the best (but not only) way to spot desert bighorn.

You Can Help

If you want to help save the bighorn and increase their numbers in California, there are several organizations you can join such as the Bighorn Institute and the Anza-Borrego Foundation. To learn more about the Peninsular bighorn, purchase a book at the Visitor Center or view the 18-minute video about the sheep in the Visitor Center theater.

The "borrego cimarrón" 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.

BIGHORN SHEEP of the PENINSULAR RANGES FACT SHEET
Compiled by Mark Jorgensen, March 2000

• Listed as a Federal Endangered Population in March 1998.
  
  

• Population in 1979 estimated at 1,180 bighorn. In 1996 estimate was 280. In 1999, 335.
  
  

• Summer waterhole counts have been conducted every year since 1971. A helicopter survey of the Santa Rosa and San Jacintos has been done yearly since 1983.
  
  

• In the 1970s and 1980s disease was responsible for high levels of lamb mortality.
  
  

• Beginning in 1995, summer watering areas in Coyote Canyon were closed to human activities between June 15th and September 15th. The closure is now June 1st to October 1st.
  
  

• In 1987, using a helicopter and netgun, 117 cattle were captured from throughout the park.
  
  

• Bighorn water systems (guzzlers) have been constructed in 10 locations to restore water sources lost to activities such as mining, homesteading and cattle ranching. The most recent one was built in June, 1999. Monitoring shows most are used by bighorn during the summer.
  
  

• The biggest threat to Peninsular bighorn today is the loss of critical habitat to development in the Coachella Valley/Palm Springs area. In 2000, there are 20 proposed golf course/housing projects in bighorn habitat. 100 courses already exist in the Coachella Valley.
  
  

• Of the 140+ radio-collared bighorn in the Peninsular Ranges since 1993, 61 have been killed by mountain lions. 69% of all mortalities in the park study area have been attributed to lions Monitoring continues w/CDF&G and UC Davis.
  
  

• The Bighorn Institute in Palm Desert has documented several bighorn deaths caused by motor vehicles, two by ingestion of oleanders, one by parasites and some to mountain lions. In 1998-99, two large rams and one ewe were killed by cars in Anza-Borrego, the 1st such deaths known in decades.
  
  

• Comprehensive helicopter surveys conducted by Fish & Game, State Parks, UC Davis, and Bighorn Institute occur every two years. In 1994 the estimate derived from the survey was 363 bighorn. The '96 flight yielded 277 sheep, a decline of 23%. In October 1998, a 15% increase was noted with the estimate rising slightly to 335 sheep.
  
  

• Recommendations to the Park by UC Davis researchers:
  1. Avoid habitat fragmentation.
  2. Limit urban development and exotic plants near sheep habitat.
  3. Continue monitoring population trends via waterhole and helicopter surveys.
  4. Initiate or support a study of mountain lion predation on bighorn.
  5. Investigate causes of chronic low lamb recruitment in the N. Santa Rosas.
  6. Continue monitoring lamb recruitment of individual ewe groups.
  7. Continue efforts to remove non-native tamarisk trees from water sources.