YUMA - The recently completed survey of the desert bighorn sheep population on the U.S. Fish and Wildlife Service's Kofa National Wildlife Refuge in southwestern Arizona resulted in a population estimate of 402 sheep.
The survey estimate is down from the 2009 survey estimate of 410 sheep, but it is still slightly above the lowest recorded estimated level of the 2006 survey of 390.
Due to standardized survey methodology and scientific margin of accuracy, biologists' analysis of the past five surveys indicates no significant decline or improvement to the herd's population.
Wildlife management agencies remain concerned about the low population levels on the refuge compared to the estimated 812 animals of the 2000 survey.
Once a very robust population, the size of the herd on the refuge has dropped significantly since 2000. Wildlife experts attribute the decline to a variety of potential factors including drought, predation, water availability, disease and human disturbance.
Due to the significance of this sheep population, the U.S. Fish and Wildlife Service and Arizona Game and Fish Department are conducting an ongoing, joint study to collect data on these and other suspected causes of the population's decline.
Seasonal rains in 2010 were good, consequently, habitat conditions are also favorable throughout the refuge.
All of the sheep appeared healthy during the aerial surveys.