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Recovery of the Desert Bighorn

Desert bighorn sheep on the refuge / C. Rodden, USDODPrior to European settlement, desert bighorn sheep were widespread throughout the southern half of New Mexico, including San Andres National Wildlife Refuge where they flourished.

From San Andres National Wildlife Refuge's designation in 1941, a native desert bighorn sheep herd grew in numbers from 33 to 140 in 1950. Five years later, the population was cut in half when a severe drought made it difficult for the herd to find the grass and other plants they needed for foraging, especially when competing with the area rancher's livestock.

But the bighorn's fortune changed again when White Sands Missile Range was established in 1952. The Missile Range eliminated livestock grazing and the bighorn sheep responded to increased food availability and the lack of human disturbance. The herd slowly increased and by the mid-1970s, about 200 desert bighorn were clambering over the refuge’s high peaks and cliffs. 

Then in 1978, psoroptic mites (or scabies) showed up on five rams harvested during a refuge bighorn hunt. The deadly disease spread rapidly and by 1979, only about 75 bighorn remained. Despite attempts to capture, treat and return healthy desert bighorn sheep to the San Andres Mountains throughout 1979 to 1981, the population continued to dwindle until only the one lone desert bighorn ewe remained in 1997.

In 1999, biologists released six rams captured from the Red Rock Wildlife Area of New Mexico to study whether they would become infected with scabies and determine if there were any other bighorn left on the mountain range. Fortunately, the rams and the last native ewe tested negative for scabies, and a dramatic transplant of wild desert bighorn to the refuge commenced. Fifty-one desert bighorn sheep from Red Rock and Kofa National Wildlife Refuge in Arizona stepped out into their new home on San Andres National Wildlife Refuge in late 2002. Today, the future once again looks bright for the desert bighorn sheep on the refuge with this herd numbering over 100 animals and slowly increasing in size.

And what happened to the last native ewe? She not only survived, this remarkable bighorn went on to give birth to two lambs (a ram in 2002 and a ewe in 2003) before she died in December of that year at 14 years old. Thanks to her resiliency, the genes of the original herd continue in today’s desert bighorn sheep.

The desert bighorn recovery story – from one lone remaining bighorn in 1997 to more than 100 today – is a tribute to people’s care for a graceful animal superbly adapted to life in the desert.
Page Photo Credits — Desert bighorn sheep on the refuge / C. Rodden, USDOD
Last Updated: Jun 18, 2014
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