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).  The Arizona Game and Fish Department (AZGFD) Research Branch is working in conjunction with the AZGFD Yuma regional office, U.S. Fish and Wildlife Service, and the U.S. Army Yuma Proving Ground Conservation Program.

Approach:

We have conducted a capture operation each November from 2007 through 2009.  We fitted thirty two adult ewes on KNWR with Global Positioning System (GPS) collars with satellite uplinking capability and thirty one bighorns (12 adult ewes and 19 adult rams) on YPG either with store-on-board, GPS collars or satellite collars as on KNWR.  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.  Bighorn 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 most current estimate in 2009 was approximately the same at 410 bighorns.  The reasons for the bighorn 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.  Information obtained on YPG will provide knowledge of bighorn habitat use and movements and possibly insight on the potential impact(s) of disturbance on bighorn movements.  Additionally, locations from YPG collars will highlight travel corridors used by bighorns, particularly rams, when traveling between mountain ranges, so that measures may be taken to protect these important sites.   

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