Do you know why bats hang upside down?

Prof. Know Why answers:

There are nearly 1,000 species of bats, worldwide. They range from the tiny bumble-bee bats of Thailand, to the vulture size Fox bats. Their wingspans range from as short as 6 inches to as long as 6 feet in length. Their diet consists primarily of insects, though some species eat nectar and fruits. But, the vampire bats drink blood of other animals. And, remember for your general knowledge -bats are the only mammals that can fly.

The most amazing fact about the bats is that they spend most of their time by hanging upside down! Bats have special kind of feet joints that let them lock their feet in a tightly clasped position (without the use of any muscle), with the weight of the body keeping the foot locked. Bats roost this way by their hind feet. And special valves in their circulatory system keep blood from rushing to their heads as they hang upside down.

But why do the bats hang upside down? There are a few different reasons why bats roost this way. Bats have the ability to go into a form of hibernation at will. This is called torpor. When cold weather reduces feeding opportunities, the bats opt to sleep through the cold by hanging upside down. When a bat is in torpor, it uses little energy to maximize the use of its body fat for surviving through the cold period.

Again, hanging upside down is also a great way to hide from danger. During the day time when predators like “birds of prey” are active, bats huddle up at such secluded spots, like the roof of a cave, the underside of a bridge, the inside of a hollowed-out tree, etc, where enemies wouldn’t think to look or reach.. This allows them safety, until the night.

Another reason for hanging upside down is that it puts them in an ideal position for takeoff. Unlike birds, bats can't fly into the air from the ground. Their wings don't produce enough lift to take off from a dead stop, and their hind legs are so small and underdeveloped that they can't run to build up the necessary takeoff speed. So, they use their front claws to climb to a high spot, and then fall into a flight. By sleeping upside down in a high location, they stay ready to launch, if they need to escape the roost.

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