Why bats hang upside down when they sleep.

dơi - Ảnh 1. — Bats can hang upside down easily thanks to the evolution of their muscles, tendons, and claws - Photo: REUTERS

Sleeping upside down helps bats easily avoid predators.

Bats hang upside down using their muscles, tendons, and claws.

This unusual behavior may be the result of an evolutionary process that enabled bats to fly, according to Tara Hohoff, a bat biologist and coordinator of the Illinois Bat Conservation Program. "As bats evolved from land-dwelling mammals to flying animals, they started by gliding like flying squirrels," Hohoff said.

The ancestors of modern bats may have climbed tall trees and then dropped down to glide between the trunks. Perhaps this is how they developed strong limbs for climbing, according to Alexander Lewis, a bat researcher at California Polytechnic University, Humboldt. Over time, these powerful arms evolved into wings.

Because bats don't have hollow bones like birds, they aren't as able to lift their bodies while flying as birds. Therefore, bats still have to "hang upside down in order to drop down and start flying," Hohoff explains.

Most humans would find it very difficult to hang themselves from a cliff or any surface, whether upside down or right side up. However, bats can hang upside down much more easily thanks to the evolution of their muscles, tendons, and claws.

"When bats find a place to land, they contract the muscles attached to their claws and open them," says Daniel Pavuk, a zoologist and chair of the biology department at Bowling Green State University in Ohio. "When the claws touch the surface, the bat relaxes its body. The body weight stretches the tendons connected to the claws."

As a result, the bat's claws grip the surface tightly to perch. "The joints of the claws lock together, and their body weight helps them hold on," Pavuk explains. In other words, bats don't need to expend much energy to hang upside down. Their bodies are relaxed, and gravity does the rest.

Helping bats avoid predators.

Unlike humans, bats can hang upside down for extended periods. According to the Iowa Department of Natural Resources, while this posture can cause blood to pool in a person's head, leading to health problems, the bat's compact size allows its heart to easily pump blood throughout its body.

After hanging upside down became their preferred resting position, this lifestyle spurred the evolution of several other traits. "The bat skeleton evolved to be lighter to support flight," Pavuk explains. For that reason, "their leg bones can't support their body weight for extended periods." Thanks to hanging upside down, bats don't need to use their weak legs to support their bodies.

Perching upside down also helps bats avoid some predators, Pavuk says. Clinging to hard-to-reach places, like cave ceilings, can help them avoid enemies like owls, hawks, and snakes. Bats can still take off when on the ground, but "it's much harder than starting to fly from an upside-down position," Pavuk explains.

However, not all bats sleep upside down. For example, discus bats in Central and South America have special suction cups on their thumbs, allowing them to cling to the underside of leaves at various angles.

Further research into the evolution of flight and the habit of hanging upside down in bats would be fascinating, as they are the only mammals capable of flight. "Some species seem to have a greater ability to take off from the ground, so studying these morphological differences would help us understand them better," Hohoff shared.

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Source: https://tuoitre.vn/ly-do-doi-treo-nguoc-khi-ngu-20250203080956299.htm