Their eyes are unable to detect color, yet the complex process of echolocation allows them to discern objects as fine as a single human hair. Bat echolocation is estimated by some to be a billion times more efficient than any similar system created by man. Echolocation is the process bats use to omit high frequency sounds, detect the waves returning from an impact with an object, and calculate the distance while in flight. Hibernation Migration Hibernating bats inhabit northern regions and their body functions are considerably slower. The bat's heartbeat and blood flow are almost quiescent, and it may take a breath no more often than every three minutes.
Digestion completely stops and energy is obtained from fat stores.
By the time spring comes around nearly a third of the bats body weight has been lost. Hibernating bats do not continuously sleep, and they move about to drink because water is lost through the thin membranes around the wings, ears, and tails. Their are species of bats who can resist short-term exposure to subfreezing temperatures, enabling them to survive in cliff faces, etc. Bats that migrate almost always return to the same cave using a strange combination of visual orientation and some unknown navigation tool. Bats often only have one or two children through the course of a year, and the pregnancy lasts about two months.