Hibernating little brown myotis (Myotis lucifugus), covered in moisture condensation in an abandoned Wisconsin mine. In the far North, these bats may have to hibernate for as long as eight months, making them especially vulnerable to white nose syndrome, a recently introduced fungus which depletes fat reserves and has caused massive mortality. Hibernation

Bats are among the most fascinating group of mammals on the planet. They live on every continent except Antarctica, have enormous impact on ecosystems and human economies, and at over 1,300 species, make up for nearly 25 percent of all mammals! They are also extreme hibernators. There is a difference between hibernation and other similar adaptations that allow organisms to survive periods of inhospitable conditions. Hibernation refers to the time period when mammals undergo very specific metabolic changes upon entering winter dormancy. There are other types of dormancy, such as diapause (when an insect or other invertebrate suspends development during these conditions) and brumation (which is how reptiles and amphibians tackle the harsh winters of our area).

In Western New York, there are two generic types of bat — cave dwelling hibernators and migrating hibernators. In late August and September, both of these types gather together and mate in what is termed the “fall swarm.” Gestation is delayed until spring, when many bat species form “maternity colonies” to spend the summer raising their pups. After mating, the migratory bats travel several hundred miles to the south, and the cave dwellers travel to relatively nearby (50 — 150 miles) cave systems to spend the winter. Bats migrating from New York end up in southeastern states like Georgia and the Carolinas. They still hibernate, and species like the eastern red bat (Lasiurus borealis) are capable of withstanding temperatures as low as 23∂F as they roost in trees during winter. Eastern reds and hoary (Lasiurus cinereus) bats have also been found to roost in leaf litter on forest floors.

Several species of bat will often utilize the same cave system, but they generally don’t compete with each other for space. They have evolved different preferences for temperature and humidity and will roost in clusters or singly as these preferences dictate. Let’s look at the little brown bat (Myotis lucifugus) as our example. For a bat species that maxes out at just under 10 grams (and that is a BIG one), they need to budget their fat stores very well to survive hibernation. Little browns are capable of consuming around 1,000 insects per hour and have high metabolism during summer in order to digest such large amounts of food. In winter, their metabolism nosedives. Normally, a bat’s heart rate ranges from 200-300 beats per minute. While hibernating this can drop to just 10 beats per minute. That means their heart is pumping once every 6 seconds! They may take a breath only once an hour, and their body temperature may approach the freezing point (with a normal body temperature of around 100∂F). All of these changes allow them to reduce their energy use by around 98 percent. Essentially, when in deep hibernation, the little brown bat almost completely shuts down as a living organism. While the details may vary, these changes are very similar for the other bat species that hibernate in this manner.

These extreme adaptations leave hibernating  bats at extreme risk. Undisturbed periods of dormancy are necessary for bats to survive hibernation. Without access to food or water, premature arousals can be fatal in just one minute. This is why White Nose Syndrome (WNS), a response to an infection from the cold-loving fungus Psuedogymnoascus destructans has been so destructive to bat populations in the northeastern United States. WNS disturbs hibernating bats, causing them to dehydrate or starve to death. Declines of 90-99 percent in infected caves has occurred, and some of the most common mammal species in North America (such as the little brown bat) have disappeared from parts of their original range. This is true in New York, where WNS was first discovered. To date, around 6 million bats have died.

Historically, cave systems were safe places for bats to hibernate. Very few creatures are active in these ecosystems, and roosting high up on cavern walls protects them from predation. Unfortunately, human activities have often meant doom for many cave dwelling bat colonies. Unwitting spelunkers, vandals, poorly placed fires, and those out to intentionally eradicate bats have all contributed to population losses in many species. Governmental agencies seeking to enhance access to caves for park attendees have altered air flows and rendered some cave systems useless for hibernating bats as well.

Given the many conservation issues facing bats, it is crucial that they be given safe habitat to hibernate, as well as rear their young in the summer months. Please give these amazing creatures a chance! Some may find them creepy, but the services they provide to ecosystems, human health and economies are irreplaceable. For more information on bat biology and conservation please contact Jonathan Townsend, CWC Conservation Lands Manager, at jonathan@chautauquawatershed.org.

The Chautauqua Watershed Conservancy is a local not-for-profit organization that is dedicated to preserving and enhancing the water quality, scenic beauty and ecological health of the lakes, streams, wetlands and watersheds of the Chautauqua region.  For more information, call 664-2166 or visit www.chautauquawatershed.org or www.facebook.com/chautauquawatershed.