2008 survey results released for Kofa bighorn sheep Populations remain low, management agencies’ concern is still high
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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 is estimated at 436 sheep.
The survey estimate is down from the 2007 survey estimate of 460 sheep, but it is up from 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 three 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.
Seasonal rains were fair to good and improved habitat conditions throughout much of the refuge. All of the sheep appeared healthy during the aerial surveys. Biologists observed lamb-to-ewe ratios of 29 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.
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.
“We recognize the importance of Kofa’s bighorn sheep and will continue to be proactive in managing this unique resource,” said Mitch Ellis, manager of the Kofa National Wildlife Refuge Complex. “We’re also confident that effective and appropriate wildlife management within the wilderness context of Kofa will be achieved.”
In November 2007, 30 ewes were captured and fitted with tracking devices in order to monitor nutrition, movements, and mortality to assist in making active management decisions to assist in restoring the herd’s population. Testing results for pneumonia on captured sheep were negative; however, lab results for other disease analysis of blood samples are still pending. The project study is scheduled to run through the fall of 2010.
“The importance of the health of the Kofa bighorn sheep population remains extremely important to restoration efforts of the desert bighorn sheep in the entire southwest,” says Gary Hovatter, Arizona Game and Fish chief of staff. “We remain committed to our active management and monitoring approach to improve the herd to its historic average population numbers.”
An extensive Web site dedicated to the Kofa NWR bighorn sheep is available at www.azgfd.gov/kofa. The AGFD launched the site in November 2007. Everything from the latest updates, background information, frequently asked questions, past press releases, active management activities and more can be found at this one-stop resource center.
For the full version of this article, visit www.azgfd.gov/pdfs/w_c/bhsheep/2008surveyresults.pdf.