The way bats rest is quite unusual in the animal kingdom. While other animals sleep upright, bats sleep upside down with their heads down. So, what are the benefits of this "hanging sleep"?
It turns out that bats have short hind legs that can't support walking, so they can only crawl with their front legs. However, if they crawl, they're slow and clumsy. What's worse, their hind legs can't jump and can't support them taking off from the ground as quickly as birds. Therefore, bats can't fly on the ground and must climb to a high place to glide for a while before taking off. Such a slow reaction speed is obviously not conducive to protecting themselves. If bats nest on the ground and rest lying down in their nests like other mammals, things would be very bad. Because once predators arrive, they can't run fast or fly away, so they can only wait to be eaten.
However, hanging upside down at a high place is a good choice. Firstly, it offers a wide view. Secondly, if there's any unusual movement, they can take off quickly. Moreover, bats' skin is very sensitive, and it's uncomfortable to bump into things. But hanging upside down is different. Except for their toes grasping things, they're surrounded by air and don't have to worry about hard objects scratching their precious wings.