Background:
Desert bighorn sheep are prominent and popular symbols of Arizona’s desert mountain ranges.  Recent advances in wildlife tracking technology allow far more intensive and precise monitoring than previously possible, providing new insight into desert bighorn movements, habitat use, and watering patterns, particularly during hot summer months when water and other resources may be important factors.

Location:
We are working at two sites in southwestern Arizona, the Kofa National Wildlife Refuge (KNWR) and the U.S. Army Yuma Proving Ground (YPG).

Approach:
We conducted a capture operation for Phase I of the study in November 2007.  We fitted fifteen adult ewes on KNWR with Global Positioning System (GPS) collars with satellite uplinking capability and nine bighorns (7 adult ewes and 2 adult rams) on YPG with store-on-board, GPS collars.  In November 2008, we conducted a second deployment of satellite-uplinking GPS collars; 15 adult ewes on KNWR and 5 adult ewes and 10 adult rams on YPG.  All collars have a 2-year operational lifespan, collecting two locations per day for nine months of the year and one location per hour during daylight hours from June through August.  Sheep status is monitored in real time (satellite-uplinking units) or by monthly VHF relocation from fixed-wing aircraft (store-on-board units).  After retrieval, location data will be downloaded from the collars and analyzed using Geographic Information System (GIS) software and data layers reflecting water resources, topography, plant communities, plant phenology, proximity to roads, and other potential disturbance factors.

Benefits: 
Though desert bighorn sheep populations are faring well in a number of areas, thanks in large part to successful restoration efforts, some populations have experienced declines.  The bighorn herd on KNWR is a notable example, having decreased from the long-term average of 800 animals to a historic low of 390 animals in 2006.  The reasons for the sheep decline on KNWR are not well understood.  Information developed from this study may provide insight into habitat-related factors affecting this population and will help guide management efforts by the Department and federal land management agency partners.

For more information contact: 
Bob Waddell, Arizona Game and Fish Department
5000 W. Carefree Highway, Phoenix, AZ 85086
Phone: 623-236-7273; Email: bwaddell@azgfd.gov