Research & Conservation

Dan Taylor films bat response to low water levels at a trough on the Gila National Forest

To gain a better understanding of conditions on the ground, BCI biologists and partners from the USDI-Bureau of Land Management, the USDA-Natural Resources Conservation Service (NRCS) the USDA-Forest Service, Red Willow Research, Inc., and the Western Bat Working Group evaluated approximately 500 livestock water developments on rangelands in 11 western states. At each water development information was recorded on tank size, configuration, water level, obstacles, and escape structure presence and style.

Fewer than 10% of the troughs had a functioning wildlife escape structure and almost 60% were dry or had water more than 6 inches or more below the rim. More than half of the troughs had some type of obstruction over the water, most commonly bracing and fencing, followed by bars, wires, vegetation, float valves, and algae.

In 2004 and 2005, the Water for Wildlife Project Coordinator worked with scientists from the NRCS, Northern Arizona University, the Arizona Game & Fish Department, the Gila National Forest, and Southern Utah University to conduct field experiments on bat response to obstructions and changes in water levels. In order to estimate the sizes of open water surfaces required for bats to drink, the Project Coordinator analyzed data collected by BCI and colleagues representing more than 40 years and 10,000 bat capture records from 39 different pools and tanks of known sizes. To test escape structure effectiveness, BCI conducted a series of escape structure trials with bats representing the range of flight morphology.

Even the most maneuverable bat species needed three to six times as many passes to reach the water surface at 10 foot diameter round and 14 foot long metal troughs obstructed by fencing or wooden bracing as they did at unobstructed waters of the same size (Tuttle et al. 2006). When water levels were lowered by 12" in two 14-foot long rectangular troughs and a six-foot diameter trough, bats needed an average of 2.7 times as many passes to obtain a drink compared to when the toughs were full.

These analyses provided the first scientific basis for recommendations on trough and tank dimensions and escape remedies and along with the livestock water trough evaluation, helped guide the recommendations in the recently published comprehensive handbook on livestock water developments and wildlife, "Water for Wildlife, a Handbook for Ranchers and Range Managers".

The Program is also initiating special demonstration projects to show how improved wildlife and livestock water development designs can dramatically increase the numbers and diversity of bats. Our BCI, is collaborating with range managers and biologists at the Cabeza Prieta National Wildlife Refuge in Arizona, the Department of Defenses White Sands Missile Range in New Mexico, and the Humboldt-Toiyabe National Forest in Nevada to monitor existing wildlife and livestock waters deemed poor for bats, then re-developing or adding new, bat-friendly water sources, and re-monitoring to demonstrate how minor modifications to water size and configuration can greatly increase bat use.