Once among the most abundant forest bats on Martha’s Vineyard, the Northern long-eared bat has become so diminished that finding even one is cause for celebration.
Last Wednesday evening, it was time to celebrate.
As part of a bat tagging effort, five biologists from BiodiversityWorks gathered at dusk and set up nets at Long Point Wildlife Refuge. After hours of catching only big brown bats, the group trapped a Northern long-eared bat.
The team quickly attached a tiny tracking device, which weighs less than 5 per cent of the bat’s body weight to avoid interfering with the bat’s flight. They used skin-safe adhesive, the same type used to attach ostomy bags, to secure the tracker on the creature’s back.
By following the tagged bat, researchers hope to learn more about where it spends its time and which structures it might use for shelter during the winter.
The BiodiversityWorks team was led by director Luanne Johnson, who, with her team, has been tracking Northern long-eared bats behavior for years. In the last few decades, the species has been nearly wiped out by the spread of white-nose syndrome, a fungal disease first detected in North America in 2006.
The disease thrives in cold environments and infects hibernating bats. The fungus grows on bats’ skin, often appearing around their noses and wings, and disrupts the hibernation process.
Since its emergence in North America, the disease has killed millions of bats. Northern long-eared bats in particular have been hit hard, and Ms. Johnson estimates their population has declined by at least 95 per cent.
Ms. Johnson and her colleagues have worked with biologists on Nantucket as well as the New York State Department of Environmental Conservation to study these bats across northeastern coastal islands, where their survival rates have been higher.
“What we learned is they’re not necessarily surviving because they’re resistant to this fungus,” she said. “They’re surviving because our winters are shorter. They have a shorter infection period here, and they can get infected, but they can survive it. It doesn’t kill them.”
Additionally, instead of hibernating in caves as they often do on the mainland, bats here have found a new spot that appears to be more disease resistant: crawl spaces beneath homes.
“At some point in history in coastal New York and Massachusetts, once humans began building dwellings with below ground spaces that stay cold, damp and frost-free in the winter, Northern long-eared bats discovered [crawl spaces] and began using them instead of migrating inland to a cave or mine. This is likely because migration takes energy and uses up fat reserves…if you could find what you need close to your summer range, why not just stay put?” Ms. Johnson said.
When bats use crawl spaces, they leave in the spring, often without ever being detected by homeowners. But Ms. Johnson says there is little cause for concern.
“We do not find a lot of Northern long-eared bats together in one crawl space. Instead, it is two to six tiny bats hibernating together,” she said. “When they are in crawl spaces beneath homes, they do not chew wires or insulation or leave a lot of droppings like mice. Instead, they just rest until spring.”
Thus far, BiodiversityWorks researchers have found very few hibernation sites and are looking to learn more about the spaces the bats select and why, as well as how biologists can better support the bats by building hibernacula — protected shelters — for them.
They hoped the field work last week would bring them one step closer.
“We’ve been trying to better understand the types of places that they’re using under houses,” Ms. Johnson said. “We’re trying to identify those types of houses, and we’re trying to build spaces for the bats to use so that they’re not vulnerable.”
After measuring the one Northern long-eared bat they found and tagging it, Ms. Johnson held it in her gloved hands to prepare for release. She raised her hand toward the sky and urged the bat back into the wild. The researchers hoped to see where the bat would lead them this winter, but some variables were out of their hands.
A week after tagging the bat, the team learned the tag had been incorrectly coded, and no information was received. The team was back at square one, disappointed but still determined to find answers.
“It has been too windy to net again, but we will be out again soon,” Ms. Johnson confirmed.