Heated boxes may stave off fungus that kills bats: researchers
Study of healthy bats in cave about to begin in Manitoba with U.S. help
Researchers in Canada and the U.S. say they think putting heated bat boxes in cold caves during the winter may help lower the number of bats dying from a fungus.
White-nose syndrome, or WNS, has killed hundreds of thousands of bats in the past two years in the northeastern U.S. The syndrome, which appears to be spreading, is of concern because bats eat insects at night and fewer bats could mean an increase in the number of insects that feed on crops.
Bodies of emaciated bats have been found on the floors of caves and scientists think the bats starved to death during hibernation. The bats were found with a white fungus growing on their faces and wing membranes. It grows everywhere on the bats, including in their pores.
The syndrome was discovered in the winter of 2006 in upstate New York, but scientists identified the fungus species only last month. The number of bats dying from it is alarming scientists. The syndrome been found in at least 55 caves in seven states.
Two ecologists — Craig Willis, an assistant professor at the University of Winnipeg, and Justin Boyles, a graduate student in biology at Indiana State University in Terra Haute — say they think the syndrome is disrupting hibernation patterns.
That means bats with the syndrome are using more energy or fat reserves to stay warm than they otherwise would when roused from hibernation during winter months.
Willis and Boyles, in a paper published this week in Frontiers in Ecology and the Environment, suggest that heated bat boxes placed in caves could be used as a "stopgap measure" to reduce the numbers of deaths from the syndrome.
"We don't know where this syndrome came from," Willis said Thursday. "We don't know whether it is caused by humans or not. We need to take steps to prevent its spread to protect this wildlife species."
As part of their hypothesis, the researchers plan in the next few weeks to put a heated bat box in a cave north of Grand Rapids, Man., to test whether healthy bats will actually use a heat source. The pilot study is receiving funding from the U.S. Fish and Wildlife Service.
If the bats fly in and out of the heated bat box, which is as big as a cereal box with a heating coil and thermostat, then the next step will be to study bats with the syndrome, provided that the study itself does not increase the spread of the syndrome. The researchers do not want to test it on affected populations if it means the populations spread the syndrome during summer months.
The bats to be studied in Manitoba, about 200, have already been implanted with microchips. An antennae attached to the heated bat box will record their movement.
Boyles said the research has important implications.
"White-nose syndrome is decimating populations of bats. These bats are the only predators of night-time insects. If you take these predators out of the ecosystem, we will see increases of forest pests and crop pests. The predators would have to be replaced by pesticides. From an ecological standpoint, it's important. And it could have an economic impact as well," he said.
Boyles said the researchers are trying to keep bat populations alive until scientists can find a cure for the syndrome.
Boyles said all mammals rouse themselves from hibernation periodically in winter, but when this happens too often or for long periods of time, it takes its toll. When bats rouse themselves, they use body energy to stay warm and spending too much time out of hibernation can cause them to burn through their fat reserves and starve to death.
Using a mathematical model, the researchers simulated living conditions of brown bats in caves during hibernation in the wild. The model tried to gauge the effects of the syndrome on the bats.
It found that the numbers of deaths in affected populations in the wild are consistent with a large increase in the amount of time spent out of hibernation. The researchers said the results show the fungus is likely disrupting hibernation patterns.
Given the results, the researchers said one way to help the bats with the syndrome save their energy and survive the winter is to give them a heat source so that they use less body heat when they rouse because bats will fly to the warmest parts of a cave during arousal.
When the researchers altered the model to include heat sources, the model showed that mortality levels dropped from 75 to 80 per cent to as little as eight per cent.
"We are trying to give a warm spot to go to," Boyles said. "This will help them stay warm, conserve fat they have stored so that they don't starve."