WASHINGTON — Bats that sleep together may be more likely to die together, and at least one species has started to wise up, according to new research.

A study released this week on the so-called white nose syndrome, a mysterious disease wiping out bat species in North America, found that the likelihood of contracting the fatal fungal disease may depend on how social bats are during hibernation.

Starting from one cave in the New York State in 2006, white nose syndrome has killed about 6 million bats in 19 states and four Canadian provinces. The disease, named because white fungus appears on the infected skin of muzzle, ears and wings of hibernating bats, causes bats to move toward the mouths of caves or fly during day time. These abnormal behaviors use up fat reserves, causing emaciation and, finally, death.

Kate Langwig, lead author and a biologist with University of California,Santa Cruz, said the disease was transmitted at an alarming rate among bat species hibernating in dense clusters even as their populations get smaller. In other words, the more they cuddle around, the more likely they are to die from the white nose fungus.

“If they continue to cluster around each other, even if the population went from 3000 to 30, those bats are still highly aggregated and continue to form really close contacts,” she said, “They will continue to .transmit the disease because they are continuing to make infectious contacts.”

According to the U.S Fish and Wildlife Service, mortality rate of bats preyed by the white nose fungus reaches 100 percent at many sites. One bat species, researchers say, has surprised them by changing its social behavior in a possible attempt for survival

The study suggests that the little brown bat, a common species in the Northeast, is changing from a mammal that prefers to roost in packed clusters to one in which most bats sleep apart from each other.  Marm Kilpatrick, co-author of the study and a biologist with UCSC, said the change contributes to the little brown bat’s survival in smaller populations.

“That is helping them stabilizing at a lower number,” Kilpatrick said, adding that the stabilization came after 90 percent of the little brown bat population was decimated by the white nose fungus.

The study may present crucial insights about bat conservation. Researchers say the results may help them identify which species is at the greatest risk of extinction.

“We can focus management on species that are most vulnerable,” Langwig said, noting that if no cure to the syndrome is found, some species, such as the endangered Indiana bat and the Northern long-eared bat, are at grave danger.

The impact of massive bat death is still unclear. However the U.S. Geological Survey said that the insect suppression service provided by bats to U.S. agriculture is valued at $4 billion to $50 billion a year.

“Bats provide tremendous value to the U.S. economy as natural pest control for American farms and forests every year, while playing an essential role in helping to control insects that can spread disease to people,” said Dan Ashe, director of the U.S Fish and Wildlife Service, in an online statement. ““We are working closely with our partners to understand the spread of this deadly disease and minimize its impacts to affected bat species.”