For example, the heart rate of a big brown bat at rest is 250-450 beats per minute (bpm), compared to 800 bpm in flight and only 42-62 bpm while hibernating. Bats can deal with this by decreasing their body temperature and lowering their metabolic requirements through the process of hibernation, which limits oxygen consumption and focuses blood flow to a few vital organs. Because heat moves from hot areas to cold ones, this temperature difference causes heat from a bat’s body to be lost to the surrounding air, making the ability of a bat to maintain its body temperature increasingly difficult as ambient temperatures drop. The necessity of hibernation is largely dependent on temperature and food availability.Īs temperatures decline during winter, the difference between ambient temperature and a bat’s body temperature increases. What is hibernation? Hibernation is a period of metabolic inactivity that can last for months at a time. Silver-haired bats roost in trees and can spend their summers as far north as Canada but migrate to warmer areas – including our coast! – to hibernate. In this post we will focus on hibernation, but I do want to mention that we have a migratory species that is found in South Carolina during winter and is absent during summer. Some bats hibernate, some migrate to warmer climates, and some do both. There are several ways bats in the United States deal with cold temperatures and reduced or nonexistent food sources. Bats cannot eat enough to stay warm if their ephemeral food source is not available. Unfortunately, cold temperatures cause many insects to become dormant and unavailable to bats during a time they need that energy the most. Insectivorous bats must maintain their body temperature, even when surrounding conditions cool, by eating large quantities of insects. As a result, it takes a large quantity of food to keep bats active and warm.Īdd to the issue of size the fact that all our bats in South Carolina eat insects – a food source that is both ephemeral and seasonal. Being small mammals, bats follow this rule and lose heat quickly. To compensate for this rapid heat loss, small mammals have a faster basal metabolic rate than large mammals, meaning they require a greater amount of energy (i.e., food) relative to their size than a large mammal does. Small mammals have a larger surface area to volume ratio than large mammals (think of this ratio on a mouse compared to an elephant). Mammals lose heat through their skin, which can be thought of as the mammal’s surface area. Size and diet play a major role in the energetic cost of staying warm. The energy that fuels these life-sustaining bodily functions comes from food. Each mammalian species has a unique basal metabolic rate, or the rate at which their body uses energy to perform basic functions while at rest (like breathing and maintaining a heartbeat). Like all mammals, bats are endotherms, meaning they can produce and maintain their warm body temperature by digesting and metabolizing food. Two of the southeasterns are an orangey-red color while the rest are gray. This begs the question, “where do bats go in the winter?” These southeastern myotis are roosting together in the weephole of a culvert. If you are in the habit of looking at the Lowcountry sky at dusk, you may have noticed fewer bats fluttering about when temperatures cool. The winter activities of southeastern bats are as diverse as the bats themselves. What do bats in South Carolina do in the winter?
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