Temperatures slightly above freezing during hibernation allow Indiana bats to slow their metabolic rates as much as possible without the risk of freezing to death or using up fat too quickly. Hibernating bats may also survive low temperatures by sharing body heat within the tight clusters they typically form. Bats awaken periodically throughout the hibernation period, presumably to eliminate waste or to move to more appropriate microclimates. This periodic waking does not seem to affect their survival, but waking caused by disturbance can cause Indiana bats to use up large amounts of energy, which can cause them to run out of fat reserves before the end of winter, possibly leading to death.