The rise and fall of psoroptic scabies in bighorn sheep in the San Andres Mountains, New Mexico

Between 1978 and 1997, a combination of psoroptic scabies (Psoroptes spp.), mountain lion (Puma concolor) predation, and periodic drought reduced a population of native desert bighorn sheep (Ovis canadensis) in the San Andres Mountains (SAM), New Mexico, from >200 individuals to a single ewe. In 1999, this ewe was captured, ensured to be Psoroptes-free, and released back into the SAM. Eleven radio-collared rams were translocated from the Red Rock Wildlife Area (RRWA) in New Mexico into the SAM range and monitored through 2002 to determine whether Psoroptes spp. mites were still in the environment. None of these sentinel rams acquired scabies during this period, and no additional native sheep were found to be present in the range. In 2002, 51 desert bighorn sheep were translocated into the SAM from the Kofa National Wildlife Refuge in Arizona (n = 20) and the RRWA in New Mexico (n = 31). Twenty-one bighorn sheep have died in the SAM since that time, but Psoroptes spp. mites have not been detected on any of these animals, nor have they been found on mule deer (Odocoileus hemionus) sampled since 2000. We conclude that psoroptic scabies is no longer present in the San Andres bighorn sheep population and that psoroptic scabies poses a minimal to nonexistent threat to the persistence of this population at this time.