Background:
The Arizona Game and Fish Department’s Research Branch recently completed a remote video camera study that documented use of desert water catchments by numerous wildlife species, particularly during the hot, dry summer months of May–July.  While many species visit these water sources, the physiological importance of water obtained from these sources is unknown.  Recent developments in stable isotope techniques provide a means to directly estimate sources and amounts of water contained in animal tissues. Deuterium oxide (a form of water comprised of the naturally-occurring, non-radioactive heavy hydrogen isotope) can be used to “label” a water source by shifting the normal ratio of light to heavy hydrogen isotopes.  This shift can be detected in blood samples taken from animals that consume the isotopically enriched water.  When coupled with samples taken from food plants and other, non-labeled water sources, it is possible to directly estimate the amount of water obtained from each.  In 2007, we initiated a cooperative study with Dr. Blair Wolf, University of New Mexico (UNM), Albuquerque, to test and implement the use of stable isotopes to measure use of catchment water by bats and birds.

Location:
We are conducting the study at two wildlife water developments on the Kofa National Wildlife Refuge (KNWR) in southwestern Arizona.  The study sites are at an elevation of 1,600 feet and located within the Sonoran Upland Division of the Sonoran Desert Biome. Average annual precipitation is approximately 8 inches and is received during winter frontal systems and summer monsoon thunderstorms.

Approach:
In summer 2007–2009, we will artificially enrich the study waters to a level that provides a large and detectable difference from other water sources used by wildlife.  From May–July, researchers from UNM will capture birds and bats at each site and draw blood samples for isotopic analysis.  They will also collect water from other sources, as well as foliage, flowers, insects and other water-containing food items that may be utilized by these species.  The samples will be analyzed by Dr. Wolf and his colleagues at UNM.   Preliminary results have demonstrated viability of this stable isotope approach and suggest that these developed water sources are of considerable importance to bats and several species of passerine birds.  Eventually, we hope to apply these techniques to large mammals, particularly desert bighorn sheep.

Benefits: 
The importance of developed water sources to wildlife remains a subject of debate.  Our study will allow us to directly estimate the importance of these facilities to a number of wildlife species.

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