Gimme shelter

by Jim MacInnis

In 2006, scientists in New York state started noticing something odd about the bats where they were conducting research: a strange discoloration around the animals’ snouts. Two years later, similar descriptions were noted in seven other states, with the additional observation that the affected bats were also extremely thin. Conservation agencies began to advise people to stay out of local caves. Dubbed “white nose syndrome,” the discoloration is probably a symptom of a fungus infection, produced by the cold-loving Geomyces genus commonly found in caves. When this fungus afflicts bats, their hibernation is interrupted for reasons so far unknown. In their struggle to stay warm in the dead of winter, the animals use up much-needed calories and eventually starve to death.

“Bats have to survive on stored fat all winter and, if they warm up too often or for too long during hibernation, they burn their fat reserves too quickly,” says Craig Willis, assistant professor of biology at the University of Winnipeg. “All mammalian hibernators have to do so-called periodic arousals at regular intervals throughout the winter. So, while bats spend most of their time in winter at a low body temperature, they end up spending up to 90 percent of their energy on these periodic arousals. If you increase arousal time, you quickly increase the rate [at which fat is used].”

Bat populations have succumbed to the effects of this fungus with alarming rapidity. Bat mortality rates average 70 to 80 percent in affected caves. Willis and his research partner Justin Boyle, of Indiana State University, estimate that in affected regions, insect consumption by bats may have decreased by as much as 600 tonnes annually. The dramatic surge in insect populations could lead to the proliferation of insect-borne diseases or to the use of heavier dosages of pesticides on crops. To date, hundreds of thousands of bats have died in the eastern United States alone, and the epidemic shows no signs of abating.
Stopgap measures are now being put in place, while researchers fast-track their efforts to determine where the malady originated and why it is such an effective killer. With funds from the U.S. Fish and Wildlife Service, Willis and Boyle have developed solar-powered heaters designed to help bats warm up during arousal periods.

“We’ll be using a highly insulated bat house equipped with a thermostat and a heater,” explains Willis. “The boxes are equipped with special antennas so we can detect bats going in and out of the box.” Research suggests that if the temperature rises in some places in a cave while other areas stay cool, bats will migrate to the warm areas until they are ready to go back into hibernation. In this way, bats will maintain their fat reserves until spring, when the cold-loving fungus subsides. Simulations indicate that the bat mortality rate in affected caves could drop to 8 percent. Testing of the effectiveness of the bat boxes will probably begin next winter in Manitoba.

“Manitoba is a great place to test this because it is well outside the affected area,” says Willis. “This is important, because we still don’t know how the disease is spread.

Until we know for sure, it would be foolish to try in the affected area.”