A new survey shows there are about 428 desert bighorn sheep on the U.S. Fish and Wildlife Service's Kofa National Wildlife Refuge in southwestern Arizona, up from the 2010 survey estimate of 402 sheep.
Kofa bighorn sheep surveys have been conducted since 1981. Adjusting for margin of error and survey methodology, biologists say there has been no significant decline or improvement to the herd's population in the past six years.
Wildlife management agencies remain concerned about the low population levels on the refuge compared to the estimated 812 animals of the 2000 survey. Drought, predators, water availability, disease and human disturbance are listed as possible reasons behind the recent decline in number.