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Sunrise over West San Andres Mountain.  Photo taken by Refuge Wildlife Biologist, M. Weisenberger.  Ram silhouette from USFWS National Images Library. (Modified final image)
Refuge desert bighorn sheep – Ovis canadensis.  All photos on this page were taken by Refuge staff other than the photo of the single adult ram which was photographed by Jim Eckles, Public Affairs Office, White Sands Missile Range.

During the salvage operation, 49 bighorn were captured and transported to a central treatment facility. Twelve sheep were ultimately returned to the San Andres Mountains in January 1981. The population estimate in 1981, following the release of these 12, was 40 bighorn sheep. Between 1982 and 1994, bighorn numbers ranged between 25 - 35, and further declined to just one ewe by 1997.

In 1999 a cooperative project between the Refuge, University of California at Davis, WSMR, and NMDGF was initiated to determine 1) whether additional desert bighorn sheep inhabited the San Andres Mountains (in addition to the known ewe), and 2) whether transplanted sentinel rams would obtain scabies. Funding for this project was provided by the National Fish & Wildlife Foundation. Six bighorn rams were captured at the Red Rock Wildlife Area (RRWA) near Lordsburg, New Mexico operated by the NMDGF, and transplanted to the San Andres Mountains. Each of the rams was outfitted with a satellite radiocollar and released throughout the mountain range. These sentinel bighorn, in addition to the sole remaining ewe, were monitored for two years and captured every 4-6 months to test for scabies infestation. At the conclusion of the study, no additional bighorn had been observed and none of the bighorn tested positive for scabies. Five additional rams, fitted with satellite radiocollars, were transplanted from the RRWA to the Refuge in November 2001.

In November 2002, 51 desert bighorn sheep were released on the Refuge in the very first augmentation to restore this herd. Twenty (18 ewes, 2 rams) of these bighorn were captured on the Kofa National Wildlife Refuge near Yuma, Arizona, and 31 bighorn (13 ewes, 18 rams) were transplanted from the RRWA.

The current population of desert bighorn sheep on the Refuge is 80-100. All lambs were born on the Refuge, including two by the last ewe from the indigenous herd. See memorial page.

In November 2005, 30 sheep were captured and transported from Kofa National Wildlife Refuge to San Andres National Wildlife Refuge. These sheep are part of an exchange agreement between the states of New Mexico and Arizona. Arizona has received 60 Rocky Mountain bighorn sheep from New Mexico in exchange for 60 desert bighorn sheep. With the November 2005 transplant the exchange is nearly complete. Ten additional sheep will be captured at Kofa National Wildlife Refuge and moved to San Andres National Wildlife Refuge at some time in the near future.

Page last updated March 2007

 

DESERT BIGHORN SHEEP

At the time San Andres National Wildlife Refuge was established in 1941, 33 bighorn sheep inhabited the Refuge. In 1950 the population peaked at 140, but by 1955 the estimated population dropped to 70. This decline was attributed to severe drought, an overpopulation of desert mule deer, overgrazing by domestic livestock, and human disturbance during former annual deer hunts. Livestock grazing was completely eliminated in 1952 with the establishment of White Sands Missile Range (WSMR). The bighorn population increased through the 1960s and stabilized at an estimated 200 sheep during the mid 1970s.

In an October 1978 bighorn hunt, psoroptic mites, or scabies (Psoroptes spp.), were detected on five rams harvested. The bighorn herd was monitored over the next several months and it was apparent the infestation was widespread. By November 1979 the bighorn population estimate was 80 animals, at which time the U.S. Fish and Wildlife Service, WSMR, and the New Mexico Department of Game & Fish (NMDGF) initiated a salvage and treatment operation.

November, 2005 release of Kofa NWR desert bighorn sheep ewes onto San Andres NWR.  Photo taken by Refuge Volunteer, Guy Powers.
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