Despite the similarities that our nine Adirondack bat species share not all of these bats have the same habits. How they each deal with the winter season is one difference.
When winter approaches and their food sources diminish bats respond by either hibernating or migrating. This time varies between species based upon their dietary preferences. All Adirondack bats feed on insects, but certain types of insects are more favorable to certain species.
Some bats strongly favor mosquitoes and gnats while others target various types of beetles and moths. As the seasons change and the numbers of specific invertebrates dwindle or disappear, each species of bat will respond accordingly. (Adirondack Almanac)
The big brown bat is generally one of the last to begin hibernating because it feeds on moths that linger well into the autumn, and so this bat may be seen into the early days of November (Adirondack Almanac).
Mating occurs prior to hibernation for cave bat species. The female will store the sperm until awakening in spring when her body will let fertilization occur. Newborn bats will greet the world at a more pleasant time.
Come spring, generally around mid April, [bats] begin to return from their wintering sites. (NYDEC)
Bat Species Winter Habits
All six species of New York’s cave bats spend the winter hibernating in caves and mines where they live off stored fat reserves, while the three tree bat species (hoary bats, red bats, and silver-haired bats) are migratory and fly south to dine in warmer temperatures (NYDEC).
However, each of the cave bats have differing habits when it comes to hibernation sites and behaviors.
Even though more than half the species that populate our region migrate to and then enter caves or mines that extend deep underground, all have definite preferences for below the surface. While some species proceed far from the entrance in order to reach warmer and damper locations, others favor cooler and drier spots closer to the world above. (Adirondack Almanac)
According to the New York Department of Environmental Conservation the little brown bat is most common bat in the state, and they congregate together during winter, having clusters sometimes numbering up to the thousands!
Indiana bats are also a clustering species. They tend to roost in clusters of 300-400 per square foot, however, these bats are a U.S. endangered species and half of the entire northeast population fits in just one N.Y. mine (NYDEC).
The Small-footed bat usually roosts alone or with a small cluster, but in winter clusters of 50 or more may occur during hibernation (Adirondack Ecological Center). This is the “least frequently encountered bat in the eastern U.S during winter surveys, and more than half the individuals counted reside in just two mines in the Adirondack region” (NYDEC).
Northern bats sometimes cluster with other bat species in winter, “but most are squeezed tightly into cracks and crevices in the rocks” (NYDEC). The eastern pipistrelle also rarely clusters and instead prefers to hang alone in warmer, moister portions of caves (NYDEC).
The big brown bat is the most tolerant of cold temperatures and low humidity, and though it does winter near the entrance of caves and mines it often resides inside buildings instead and is the only Adirondack bat species to regularly do so (NYDEC).
It is believed that “prior to human settlement within the Adirondacks, the big brown bat [spent] the winter in hollow trees in old growth forests,” where several would huddle together in small spaces to warm each other through the freezing winters (Adirondack Almanac).
However, the presence of year-round homes in the Adirondack Park were a gift to these bats who take advantage of any crack or crevice that allows the big brown bat to sneak in and spend a warm winter sleeping inside an attic or wall.
These bats do not often form the large clusters as do several other species, and it’s not uncommon to find a hibernation space with only one bat. Because of this isolationist behavior the big brown bats are at a current advantage compared to the other cave bats. By avoiding socialization with other bats and the caves where other bats frequent the big brown bats are avoiding contact with White-nose Syndrome, a disease that is decimating East Coast bat populations. This bat may become the future dominant bat species in the Adirondacks.