No rebound in sight for bats
White-Nose Syndrome: Small brown bat may disappear from region in little more than a decade
PETERBOROUGH — In 2006, New England states started observing a disturbing trend in the local population of bats — a fatal new fungus was killing off thousands of bats across several species lines. Seven years later, more is known about White Nose Syndrome, but the fungus that has decimated local bat populations continuous to vex researchers. And the impact is alarming: the small brown bat, once the most common bat in the Northeast, may not be found regionally within 12 years if the spread of the fungus can’t be contained.
White Nose Syndrome, caused by the fungus Pseudogymnoascus destructans, grows in the same damp conditions that bats tend to hibernate in. White in color, the fungus grows on the muzzle, ears, wings and tails while the bats hibernate. While the name is associated with the white marks that show up on the tips of the nose, the real danger is when bats get the fungus on their wings.
The fungus penetrates the thin membranes on the wings. Because the wings help bats regulate water in their bodies, the disruption causes them to dehydrate. It also happens while the bats are still for a long period of time, especially when they’re hibernating. While bats are hibernating, all their systems, including their immune response systems, are suppressed, meaning the bats can’t fight the infection. The infection causes the bats to wake up more often then they would otherwise, a process that forces them to use up the body fat they need to survive until spring.
Emily Preston, a wildlife biologist with New Hampshire Fish and Game, said that recent weight studies of bats entering hibernation have shown that bats that are a higher weight to begin with may be the ones surviving the fungus. There are many studies being done as to how to combat the fungus, she said, particularly looking at the genetics of both the fungus and the bats to see if there is something that can be done. It is believed the fungus originated in Europe and was transported here by humans who explore caves or other places where bats may hibernate, said Preston. This fungus has been found on European bats, but has not had the same deadly effect on the population, so there may be a solution to be found with time, she noted.
According to a release issued by Fish and Game in April of 2012, White Nose Syndrome was discovered in New York in 2006. By 2008, it was found in New Hampshire. In 2010, eight mines in the state were surveyed. All of them had bats infected with the fungus. In 2011, four of the largest surveyed hibernation locations only had a total of 16 surviving bats, and one mine was completely empty. Just two years earlier, those mines had been home to thousands of bats, which was one of the highest bat populations recorded. The little brown bat and the northern long-eared bat are the most heavily effected, with between 99 percent and 100 percent of the monitored population disappearing. The big brown bat, tri-colored bat and small-footed bat have also been effected by the fungus, but their numbers are harder to monitor because of their roosting habits, said Preston.
Jacques Veilleux, a professor of biology at Franklin Pierce University who helps to track hibernacula for the state, said that until 2011, he had been working in Surrey, studying the effect of White Nose Syndrome on summer captures.
“We’re seeing relative dramatic declines,” said Veilleux. In 2008, the state had its best cumulative year ever when it came to bat population, said Veilleux. The following year, numbers were down by 67 percent. The next, by 99.6 percent. In Peterborough in 2009, a summer colony of bats which had been studied for 16 years and was at least 40 years old, all but disappeared.
“The biggest concern is that bats are the biggest predator of night-flying insects, some of which are forest pests and some just nuisance insects. We have eight species of bats in New Hampshire. Five have been affected, and two have been very heavily affected, so there has to be a larger effect,” said Preston. That effect, however, is hard to measure since insect population is impacted by dozens of variables. Veilleux added that the impacts of insect booms, and following crashes, might also have longer-reaching effects.
However, in some farming states hard-hit by white nose, there is a rising reliance on pesticides, which are being used to combat pests that are part of the bat’s diet. The pesticide use may be related to the loss of local bat population.
“What effect the lack of bats has on agriculture because of the loss of a natural pest control is a concern,” said Preston. “There’s definitely an impact, including a financial impact because of the increased use of pesticides. We just can’t document how much of an effect there is, yet.”
Veilleux said people will often ask him what the importance of bats is, and the recent agricultural study suggested that the free pest control provided by bats can average $23 billion per year in pesticide savings. “That’s billion with a ‘b,’” he said.
The bat population has a slow growth rate, with females generally only producing one — sometimes two — pups a year. The loss of colonies creates a crisis in the bat population. “Their abilities to rebound are really slow, if it can happen at all,” said Preston.
Veilleux said he wasn’t confident that such a rebound could happen. “It’s probably one of the worse groups this could happen to,” he said. “They’re not like some species of rodents that can have up to 30 babies a year.” Not only do bats have a low birth rate, newborn bats have a high mortality rate in the wild. Only half will survive their first hibernation, he noted. “It’s going to be thousands upon thousands of years before we see the numbers up to what they were, if it can happen at all. This is not the only stress on bats. It’s just one more thing.”
And because they are flying creatures, bats are highly mobile, which increases the range of the fungus, since researchers speculate that bat-to-bat contact assists in the spread of the fungus. First discovered in New York in 2006, since then it has spread as far west as Missouri, and South to Georgia and Alabama and well into Canada. While bats themselves may be spreading the fungus, there are isolated pockets that researchers believe could have only been infected by human interference, by traveling from an infected cave to an uninfected one, bringing the fungus with them on their clothes.
Fish and Game recommends that cavers who are moving from cave to cave which are suitable for bat hibernation take proper steps to decontaminate their clothing and equipment before moving to the next site. Also, some locations have been closed to attempt to quarantine the situation. Preston said they ask the public to respect those closures. While that can help to decrease human contamination of future sites, there is little else that may help to curb the problem, said Veilleux.
Currently, most of the funding to research White Nose Syndrome is going toward the initial research of the fungus, particularly the DNA of the fungus. Suggestions for mitigating the problem have included using fungicide on infected sites — which brings up issues of groundwater contamination and killing natural fungi — or artificially increasing temperature in hibernacula so that bats will have a thermal refuge and not lose as much body fat should they wake up during their hibernation. Both of these pose considerable challenges and are not feasible on a large scale, said Veilleux.
“Ultimately, we have no good, plausible way to mitigate the problem. We’re just watching it unfold and shaking our heads. It’s bad,” said Veilleux.
Ashley Saari can be reached at 924-7172 ex. 244, or firstname.lastname@example.org. She’s on Twitter @AshleySaari.