Although they can't see color, bats can see better than we do at night. Bat Biology Bats, like humans, are mammals, having hair and giving birth to living young and feeding them on milk from mammary glands. By listening to the echoes reflected back to them, they can discern objects in their path. Bats are the only true flying mammals. The bones in a bat's wing are the same as those of the human arm and hand, but bat finger bones are greatly elongated and connected by a double membrane of skin to form the wing.
Bats primarily are nocturnal, although many fly early in the evening, sometime before sunset.
Occasionally, especially on warm winter days, they are observed flying during daylight hours. Reproduction and Longevity Most female bats produce only one offspring per year, although some species give birth to three or four babies at a time. U.S. baby bats are born in May or June. They develop rapidly, and most can learn to fly within two to five weeks after birth. Bats live relatively long lives for animals of their small size, some as long as 30 years.