2010 Survey Results Released For Desert Bighorn Sheep On The Kofa NWR
Populations remain low, management agencies’ concern is still high.
PHOENIX, AZ – -(Ammoland.com)- YUMA, Ariz. — 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 (USFW) and Arizona Game and Fish Department (AGFD) 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. Biologists observed lamb-to-ewe ratios of 24 lambs per 100 ewes, which is above the long-term average of approximately 20 lambs per 100 ewes for the refuge. However, a slightly higher lamb-to-ewe ratio has not yet translated into an increase in the population – it has only stabilized it.
The New Mexico State University Cooperative Studies Unit is studying the relative health of bighorn sheep on the refuge. In November 2007, 30 ewes were fitted with tracking devices to monitor nutrition, movements, and mortality to assist in making active management decisions to assist in restoring the herd’s population. The project study is scheduled to run through the fall of 2010. The ewes were evaluated in November 2010 using ultrasound technology. Body fat composition indicated good nutrition and nearly all of the ewes were pregnant. Other biological samples were collected for disease analysis and have been sent to various laboratories.
AGFD and USFWS biologists captured a male mountain lion in November 2010 on Kofa NWR. A satellite (GPS) collar was fitted on the lion pursuant to the ongoing effort to monitor mountain lions and remove lions that regularly prey on desert bighorn sheep as described in the final environmental assessment “Limiting Mountain Lion Predation on Desert Bighorn Sheep on the Kofa National Wildlife Refuge” and the AGFD Kofa Mountains Complex Adaptive Predation Management Plan.
To view the management documents and learn more about the restoration efforts of the Kofa desert bighorn sheep herd, visit the Arizona Game and Fish Department’s website at www.azgfd.gov/kofa. The U.S. Fish and Wildlife Service’s Kofa National Wildlife Refuge website is at www.fws.gov/southwest/refuges/arizona/kofa/index.html.
About Arizona Game and Fish Department:
The mission of the Arizona Game and Fish Department is to conserve, enhance, and restore Arizona's diverse wildlife resources and habitats through aggressive protection and management programs, and to provide wildlife resources and safe watercraft and off-highway vehicle recreation for the enjoyment, appreciation, and use by present and future generations.
About U.S. Fish and Wildlife Service:
The mission of the U.S. Fish and Wildlife Service is working with others to conserve, protect and enhance fish, wildlife, plants and their habitats for the continuing benefit of the American people. We are both a leader and trusted partner in fish and wildlife conservation, known for our scientific excellence, stewardship of lands and natural resources, dedicated professionals and commitment to public service. For more information on our work and the people who make it happen, visit www.fws.gov.
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