Fantastic Bats!

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Depending on the species, a hibernating colony may contain only females, while others may be coed. In nearly all cases, most females spend the winter almost pregnant — literally. Bats mate in the fall, but the female holds the sperm inactive and delays ovulation until spring, after she’s had enough time to rebuild her energy reserves. Pregnant females move to a warmer roost, or to a warmer part of the cave, forming nursery colonies. Bats are born 50 to 60 days after ovulation. The pup emerges naked and helpless, with undeveloped wings but also with tiny claws on its hind feet and thumbs, enabling it to climb up its mother to nurse. In about one month, it’ll be able to fly and feed on its own.

Flexible Fliers

If you’ve ever watched a bat dive, swoop and swerve in the sky at dusk, you know there’s no confusing it with a bird’s flight — a bat’s movements are quicker and less predictable, more aerobatic. Like birds, bats have wings that are supported by arm bones. But unlike a bird’s, each bat wing also is supported by four elongated finger bones and a short thumb: a five-digit “hand” similar to our own in basic skeletal structure. The thumbs have a little hook at the end for clinging to tree branches or cave walls. The fingers are webbed together, sandwiched between two thin layers of leathery skin that connect to the bat’s body, forming a continuous airfoil. Another double membrane connects the two hind legs. Between the wings’ layers of skin, there is no flesh at all, just bones, blood vessels and nerves.

Also unlike bird wings, bat wings are not rigid. The finger bones are thin, light and flexible, and the skin is extraordinarily elastic. With every flap, the wings billow and change shape, adapting to the bat’s directional shifts and to varying airflows. Scientists still don’t understand bat aerodynamics entirely. But one thing’s certain: The bat’s flexible wings give it amazing maneuverability, like a living stunt plane. By folding its wings into different shapes, the bat can change direction quickly, zooming and tumbling through the air. It can roll, climb,dive, somersault and even hover like a hummingbird. When landing, a bat executes a last-second flip, so that it ends up hanging upside down, with its wings folded alongside its body like a collapsed umbrella.

A bat also uses its flexible wings to snag insects on the fly. Pursuing its prey one bug at a time, a bat flexes its fingers to make a scoop in its wing or tail membrane, strikes the insect, then quickly grabs the stunned morsel with its hind feet and pops it into its mouth.

Silent Screamers

Of course, in order to catch a flying, fleeing insect at night, you have to find and follow it in the dark — not an easy task, regardless of your flying ability. No bats are blind, but insect-eating species have only fair night vision. So they use sound to track and pursue prey.

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