Bats suffering from white-nose syndrome, the fungal disease that has ravaged species across the United States, would be wise not to bunk too close together.
A research team led by University of California, Santa Cruz, scientists has found that as bat communities are decimated by white-nose syndrome, their habit of hibernating in close clusters means their numbers will continue to decline, since they continue to transfer the disease to each other at a high rate. The scientists related their findings in a paper published Tuesday in the journal Ecology Letters.
White-nose syndrome first appeared in New York in 2006, and is named after the fuzzy fungus that grows on the muzzles and wings of affected bats. The disease, which is still not well understood, has spread throughout the U.S. and into parts of Canada.
In this latest bit of research, the scientists examined data from bat population surveys conducted between 1979 and 2010, to track how populations rose throughout the years and then fell after the disease reared its head.
We found that in the highly social species that prefer to hibernate in large, tightly packed groups, the declines were equally severe in colonies that varied from 50 bats to 200,000 bats, which suggests that colonies of those species will continue to decline even when they reach small population sizes, UC Santa Cruz biologist A. Marm Kilpatrick, a co-author of the paper, said in a statement Tuesday.
But in bat species that tended to hibernate alone, declines in small colonies were much less severe.
The researchers found that at least one bat species is adjusting its social behavior, possibly in response to the disease. Little brown bats, which used to prefer roosting in tight-knit groups, are now more likely to hibernate by themselves.
Our analysis suggests that the little brown bats are probably not going to go extinct because they are changing their social behavior in a way that will result in them persisting at smaller populations, Kilpatrick said.
But being antisocial is not guarantee of immunity. The team found that 14 communities of the northern long-eared bat, a solitary roosting species, were wiped out within two years after white-nose syndrome hit.
The northern long-eared bats may be particularly susceptible to the disease, so they continue to get hit pretty hard even after transmission rates are reduced, lead author Kate Langwig said.
Two kinds of bats seem especially resilient against the disease: big brown bats and eastern small-footed bats. It's possible that these species' solitary nature helps them avoid the fungal plague, but its also possible that these bats might be hibernating in places less hospitable to the fungus that causes white-nose syndrome.
It appears that the driest and coolest caves may serve as partial refuges from the disease, Kilpatrick said.