Many bat species in Ohio hibernate during colder months. This natural survival strategy allows them to endure periods when food is scarce and environmental conditions are harsh. For bats, this occurs as insect populations disappear with falling temperatures. By entering a state of inactivity, bats conserve energy until warmer weather returns.
Understanding Bat Hibernation
Hibernation in bats is a complex biological process known as torpor, differing significantly from regular sleep. During this state, bats undergo profound physiological changes to conserve energy. Their body temperature drops considerably, often nearing the ambient temperature of their surroundings (typically 35-40 degrees Fahrenheit). This reduction is accompanied by a dramatic slowing of their metabolic rate, sometimes to less than 5% of their active rate.
A bat’s heart rate can decrease from hundreds of beats per minute to just a few, and their breathing becomes infrequent. These physiological adjustments allow them to survive for months on stored fat accumulated during warmer seasons. Without this deep torpor, bats would lack the energy reserves to last through winter when insects are unavailable.
Ohio’s Hibernating Bats and Their Winter Retreats
Several bat species in Ohio hibernate rather than migrate during winter. These include:
- Little Brown Bat (Myotis lucifugus)
- Indiana Bat (Myotis sodalis) – federally and state endangered
- Big Brown Bat (Eptesicus fuscus)
- Northern Long-eared Bat (Myotis septentrionalis) – federally threatened and state endangered
- Tricolored Bat (Perimyotis subflavus), formerly Eastern Pipistrelle – state endangered
These hibernating bats seek specific locations known as hibernacula, generally from late October to early April. Ideal hibernacula provide stable temperatures and high humidity, which helps bats prevent dehydration while conserving energy. In Ohio, bats primarily use natural caves and abandoned mines for hibernation. They can also be found in rock crevices and, for the Big Brown Bat, sometimes in attics or other old buildings, which offer a suitable temperature range.
Conservation Concerns for Ohio’s Bats
Hibernating bat populations in Ohio face significant challenges, with White-Nose Syndrome (WNS) as a primary threat. This fungal disease, caused by Pseudogymnoascus destructans, is named for the white fungal growth on infected bats’ muzzles and wings. The fungus thrives in cold, damp hibernacula.
WNS irritates bats, causing them to awaken more frequently from torpor than usual. Each arousal is energetically costly, rapidly depleting their fat reserves meant to last the entire winter. This often leads to starvation and dehydration, resulting in mass mortality. Since its discovery in Ohio in 2011, WNS has caused declines of 90% or more in some bat populations, particularly impacting species like the Little Brown Bat, Northern Long-eared Bat, and Tricolored Bat.
Beyond WNS, Ohio bats face other threats, including habitat loss and disturbance of hibernacula and summer roosting sites. Disturbances during hibernation, even by humans, prematurely expend bats’ limited energy reserves. Climate change may also disrupt hibernation cycles, further stressing populations. Given their role in controlling insect populations, bat decline has broader ecological implications.