Midwest bat populations already faced serious threats, such as the loss of habitat to development, when they were struck four years ago by a deadly disease known as white-nose syndrome. The disease is still killing bats, the endangered Indiana bat among them. How climate change will affect the situation is unclear. But just as in the case of Kentucky bats — described in a story May 11 — scientists fear climate change could add to stressors on the imperiled species.
The U.S. Fish and Wildlife Service is revising its Indiana Bat Recovery Plan, first drafted in 1983, to acknowledge that concern.
“We know that temperature is very important to survival of our insectivorous bats that hibernate in caves, including Indiana bats,” says Lori Pruitt, lead Service biologist for the species. “During winter, only a small proportion of caves provide the right conditions for hibernating Indiana bats because these bats have very specific temperature requirements during hibernation. Surface temperature is directly related to cave temperature, so climate change will inevitably affect the suitability of hibernacula.”
|A cluster of endangered Indiana bats cling to a cave wall in southern Indiana. Scientists are considering potential climate change impacts in their species recovery plan. Photo: Andrew King/ USFWS.|
Climate change models for the little brown bat, a closely related species, suggest warming will push its range north in the next 80 years. A similar range shift for the Indiana bat could reduce the bats’ access to the large, complex cave systems on which they depend; such caves are rare north of the bats’ current range. Indiana bats have also been known to colonize abandoned mines. Scientists speculate that in response to climate change the bats might colonize more mines north of the current range — if the climate inside the mines adequately mimics the cave environments to which the bats have adapted over millions of years.
|Biologists survey endangered Indiana bats in a southern Indiana cave. Photo: Andrew King/ USFWS.|
Climate change could also affect whether bats go hungry. Indiana bats are prodigious insect-eaters. During their six months of winter hibernation, they live solely on their fat reserves. When they emerge in spring, with their fat reserves depleted, their survival depends on the availability of insects. If climate change reduces the number of insects then at hand, scientists theorize, bats may be hard pressed to find enough food at this critical time.
Female Indiana bats may be particularly vulnerable when they emerge from hibernation pregnant and migrate to their summer maternity areas. There, they must eat more to support pregnancy and produce milk for their pups. If pup production doesn’t coincide with sufficient insect availability, experts worry reproductive success could decline. Indiana bats produce only one pup per year, so bat populations are slow to recover if reproduction drops.
Climate change could also disrupt bat mating and migration, biologists speculate, by altering the seasonal cues that trigger these behaviors.
Biologists are weighing possible management actions to help Indiana bats adapt to climate change. One critical step: continuing to monitor Indiana bat populations for potential shifts in hibernation sites. While Indiana bats are typically loyal to their hibernacula, returning to the same site year after year, populations can shift over time in response to changing conditions.
“As we improve our understanding of how climate change can affect Indiana bats and their habitat, we can use that information to refine our strategy for improving their odds of long-term survival,” Pruitt said.
Climate Change Focus: Adaptation
Author: Georgia Parham, U.S. Fish and Wildlife Service, Midwest Region, 812-334-4261 x1203 Georgia_Parham@fws.gov
For more information on climate change in the Midwest: Chuck Traxler, 612-713-5313, Charles_traxler@fws.gov