Some bats may only survive in remnant populations
LINZ — Even as they grapple with the devastating decline of bat populations caused by white-nose syndrome, researchers are starting to take a look at how, if and when some bats might recover from the fungal disease that has decimated colonies across the eastern U.S.
For at least one species, the outlook isn’t all that bright, according to U.S. Geological Survey scientists who took a close look at the once-common little brown bat. The scientists estimated that between 2016 and 2018, little brown bat populations that once contained millions of bats could decrease to lower than 100,000 animals. Also, some populations may not begin to increase again until around 2023.
Populations east of the 100th meridian, the designation between the drier western and wetter eastern states, would likely consist of sparse remnant communities, some of which may be less than 1.5 percent of their original sizes, the researchers found.
This scarcity of surviving bats can negatively affect reproduction rates and make survivors more vulnerable to threats.
“With so few surviving animals, little brown bats could cease to be a dominant bat species in the eastern United States,” said USGS scientist Robin Russell, the lead author of the report. “These small bat population sizes are problematic because they are more likely to be wiped out by events such as poor weather conditions and landscape development.”
Animals in small communities could also have trouble finding mates. Female bats gathering in maternity roosts during the summer can include several hundred bats, and the inability to form these colonies due to reduced populations may negatively impact overall reproduction rates.
Bats pollinate plants, spread seeds and save us billions of dollars in pest control each year by eating harmful insects. WNS, caused by the Pseudogymnoascus destructans fungus, can cause up to 100 percent mortality in some little brown bat populations. It has already killed millions of hibernating bats in North America and continues to spread.
Resource managers are pursuing multiple approaches to manage the disease, with treatment strategies to both reduce impacts of the disease and to improve the potential for bat populations to survive and eventually recover.