Ranchers build escape ramps for bats and other wildlife


Issue Date: August 26, 2009
Steve Adler

A California myotis bat swoops down to drink water from a livestock water trough. These troughs provide water for bats, as well as other mammals and birds, not to mention the livestock for which they were built.

While most of us are deep in slumber each night, a group of flyers is hard at work, tirelessly gobbling up airborne insects that target farmers' crops. These workers are, of course, bats.

"Bats are primary predators of night-flying insects that cost farmers and foresters billions of dollars annually," said bat expert Dan Taylor. "Birds are out there in the daytime eating insects, but a lot of the most voracious crop pests are night-flying insects. And the bats are the night shift. That's who is out there eating insects, helping control pest populations."

California has one of the most diverse populations of bats in the United States, boasting 22 different species that comprise more than half of the species found in the country.


Participants in a recent workshop in Livermore build wildlife escape ramps.

"Bats are found everywhere in California, from the lowest deserts to the tops of some of the tallest peaks," Taylor said. "People would be shocked to see how many bats are out there all the time eating insects."

Taylor and his colleagues at Bat Conservation International in Austin, Texas, are on a crusade to educate people about the important role that bats play in integrated pest management. At a recent workshop in Livermore, Taylor spent the day educating area ranchers-as well as representatives of county, state and federal resources groups-about ways to protect bats and other wildlife species from a little-known danger.


Escape ramps are installed in livestock water troughs.

That danger is drowning, in this instance drowning in rangeland water troughs. Taylor pointed out that bats, as well as many other small mammals and birds, can easily fall into water troughs and not be able to get back out. His solution is to outfit the troughs with escape ramps that enable the creatures to crawl back out of the water. The ramps can be made easily and inexpensively.

In order to drink water, bats must fly down to the water surface, scoop up a drink and keep flying up and away from the pool-a process that requires an unobstructed "swoop zone," just as airplane pilots need clear approaches to their runways, he explained. Obstacles in the flight path can prove deadly. Like many other animals, bats are very susceptible to drowning if trapped in a water tank without an escape route.

"Bats drink water on the fly, and when you have steep-sided troughs with low water levels, the bats can easily fall in. Also, a lot of other animals, birds particularly, will fall into a trough while trying to drink or bathe. When water levels drop, small animals like rabbits, squirrels and chipmunks fall in and drown," he said.

In addition to the loss of these animals, it also makes for poor water quality in the trough. These are conditions that worsen when there are high temperatures and drought, and water levels are low. Taylor noted that many of these deaths might have been prevented if the troughs had properly constructed wildlife escape ramps.

One of the most economical and easily constructed wildlife escape structures is made of expanded-metal grating, which is especially well suited to round and rectangular metal troughs that are no more than four feet deep. Thirteen- or 11-gauge expanded metal with 1/2-inch mesh is highly recommended. Taylor said 3/4-inch mesh is even better, but it is more difficult to find.

Among the ranchers participating in the workshop was Clayton Koopman, who said he recognizes the value of the escape ramps as a way of maintaining good water quality.

"Wildlife escape ramps protect animals from the threat of drowning in the troughs. This is beneficial to ranchers in that water quality in these troughs is not jeopardized by dead animals contaminating the water source. On the down side, the ramps do take time to build and install and cost ranchers money," Koopman said.

He said the diversity of wildlife on his ranch includes deer, hogs, turkeys, elk, squirrels, badgers, coyotes, bobcats, skunks, racoons, feral cats and occasionally a mountain lion. Many utilize the remote troughs as water sources.

Koopman noted that the ranch currently has concrete escape ramps installed in water troughs, but it plans to begin switching them out for mesh ramps similar to the ones built during the training session.

Ian Swift, a watershed resources specialist with the Contra Costa Water District who also attended the workshop, said the Bat Conservation International program for developing escape ramps is a good one because it promotes wildlife friendly practices on ranches.

"I have seen American kestrel and Western meadowlarks that have drowned in water troughs without escape ramps. Fortunately all of the water troughs in our watershed do have these ramps," he said.

In the rest of the Western United States, only about 10 percent of rangeland water troughs have escape ramps, but that number is improving.

"The good news is that these escape ramps are catching on, and ranchers and wildlife managers are starting to pay more attention to this," Taylor said.

Most bat species need open water surfaces at least 10 feet long by no less than 2.5 feet wide.

It is important to maintain consistent water availability and full water levels, especially during maternity season and drought, he said. Maternity season for bats, when the mother bats are nursing their young, generally occurs from May through August.

Another concern relating to water troughs is possible obstructions to the flight path of bats. Bracing, fencing, posts or vegetation over or adjacent to the water surface may prevent bats from drinking.

Research by the U.S. Department of Agriculture Natural Resources Conservation Service found that with 10-foot-diameter round and 14-foot-long rectangular metal troughs, even the most maneuverable bat species required several passes to reach the water surface when fences or support braces were placed over the water. With smaller water troughs, most bat species simply cannot drink where obstacles prevent them from finding a fully open swoop zone, he said.

Instructions on how to build an escape ramp using the mesh grating may be found on the Bat Conservation International Web site at www.batcon.org; download the "Water for Wildlife" handbook and look on Pages 8-9.

Guidelines for wildlife escape ramps

Several basic principles should guide the design and installation of all wildlife escape structures. An effective escape device should:

  • Extend down into the water and meet the inside wall of the trough so animals swimming along the perimeter will find the structure, rather than becoming trapped behind or beneath it or missing it entirely;
  • Reach to the bottom of the trough, so it will be effective even if water levels drop sharply;
  • Be firmly secured to the trough rim so it will not be knocked loose by livestock or other animals;
  • Be built of grippable, long-lasting materials, such as painted or coated metal grating, roughened fiberglass, concrete, rock and mortar or high-strength plastic composites;
  • Have a slope no steeper than 45 degrees so animals can climb out without slipping back into the water;
  • Be located to cause minimal interference with livestock.

(Steve Adler is associate editor of Ag Alert. He may be contacted at sadler@cfbf.com.)

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.