Roosting in dead and dying trees known as snags, these creatures work their tiny bodies under the loose bark, as a shelter against bad weather. But such trees are hard to come by in recently logged areas.
Studies by the U.S. Fish and Wildlife Service, however, suggest that the bat may be more adaptable than was thought. According to the agency’s Indiana Bat Revised Recovery Plan — partly written by biologist Mick Harvey, who found the local bats — once evicted from one tree, they may just move to another one, and they will sometimes continue to forage, even in logged areas.
But the Southern Appalachian Biodiversity Project maintains that any logging renders forests unsuitable for the Indiana bat.
“Even if the snag is there, the habitat has been nuked,” argues SABP staff attorney Marty Bergoffen. “They are much more open to predation there, the temperature isn’t right, the humidity isn’t right.”
Still, according to the Recovery Plan, the primary cause of the bat’s drastic decline isn’t logging — it’s disturbed hibernation. With its metabolism running slow as cold molasses, a bat can survive until spring just living off its fat. But any disturbance that elevates its heart rate and metabolism can eat up as much as 68 days’ worth of stored fat. Too many disturbances, and the bat may die before it can resume catching insects in the spring.
Another problem is vandalism. In the worst recorded case, in 1960, three youths tore an estimated 10,000 bats from a cave ceiling in Kentucky, trampling and stoning them to death.
In addition, blocking cave openings shuts out bats. And even non-solid gates can change the airflow into caves, altering temperatures and, thus, affecting bat metabolism. An estimated 200,000 bats have been lost at three Kentucky caves in this way since the ’50s. Other hibernation hazards include flooding, freezing and cave-ceiling collapse.
According to the Recovery Plan, changes in everything from the humidity of forests to the availability of insects can have profound effects on the bats. And there just isn’t enough information yet to draw firm conclusions.
“A clearer picture of the relationship between the Indiana bat and its summer habitat is urgently needed,” states the plan. “Until we better understand the factor or factors that have contributed to the decline of the species, we cannot accurately assess whether the loss of summer habitat … is limiting to regional or range wide populations of the species.”
— Brady Huggett