This Yawning Bat May Just Melt Your Heart

There are over 1,400 bat species in the world, and they are almost exclusively nocturnal. Bats have traditionally been classified as Microchiroptera, or microbats, and Megachiroptera, or megabats. Megabats are also sometimes called fruit bats or flying foxes. Flying foxes are Old World tropical and subtropical bats that primarily feed on plants. In this adorable Instagram post, a Ryukyu flying fox yawns and stretches to start its day as the sun goes down. How can a megabat hang upside down like smaller bats, and why are its wings translucent? Read on to find out.

The Ryukyu Flying Fox

Ryukyu flying foxes (Pteropus dasymallus) are native to the islands of the Ryukyu archipelago in Japan, as well as Taiwan and the Philippines. These bats roost in the forests and rainforests during the day, often in large groups. They tend to live in colonies with fixed roosting locations, although some subspecies may be more solitary. The bats feed on plants and plant products, including fruit, nectar, pollen, flower petals, and leaves. Fruit, particularly figs, makes up most of their diet.

These medium-sized bats weigh about one pound. They have a forearm length of approximately 5.5 inches and a wingspan of around 31 inches. The sub-species shown in the video appears to be Pteropus dasymallus dasymallus. This is the largest of the five subspecies and the darkest in color. It has a dark head and face, a dark brown to black body, dark brown wings, and cream-colored fur around its neck. These bats are important to the region because they disperse seeds and pollinate both wild and commercial plants.

Hanging Around

Most bats hang upside down to relax and sleep. When a bat wants to roost, a specialized tendon locking mechanism in its feet secures its toes and talons around the branch. With the tendons locked in place, the bat’s body weight and gravity do the rest of the work. As a result, the bat exerts very little energy while hanging. When they flex their leg muscles, their tendons unlock, releasing their toes and talons so they can fly.

Bats also roost in trees so they can take off directly into the air. Most bat species cannot stand on their hind legs. As a result, they are unable to run and gain the speed required to take off from the ground. Their wings are generally not strong enough to generate sufficient lift to overcome gravity and take off from a standing position. However, since they are already hanging in the air, they simply let go, drop, and open their wings to fly away.

Of course, if humans attempted to hang upside down for long, our blood would begin to pool in our heads. This not only makes us dizzy, but it also makes it difficult for the blood to return to the lower parts of our bodies. Bats don’t have that problem because they are so small and have relatively little blood. The largest flying foxes, which are thought to be the giant golden-crowned flying fox and the Indian flying fox, only weigh around 3 pounds. That is still too small for gravity to have an impact on their circulatory systems. So, unlike in humans, bats’ hearts can continue to distribute blood throughout their bodies.

Flying Fox Wings

Researchers found that daytime activity in Ryukyu flying foxes was observed in the forested areas, specifically during the summer months. Because the nights are shorter, the bats tend to leave their roosts earlier. So there is still sunlight when the bats awaken. The sun shining behind the bat in the video makes its wings appear translucent. This is because the wings are thin membranes of skin that stretch from the body across the bat’s forelimbs and elongated fingers, and down its sides to its ankles.

The skin of a bat’s wings has an external epidermis and an internal dermis layer that contains tiny muscles and blood vessels, which can be seen when the bat holds its wings up to the light. These small, thin muscles allow the bats to adjust the stiffness and the curvature of their wings during flight. Although the wings are often described as “leathery,” conservationists note that bats’ wing membranes are actually flexible and soft, similar to the skin on our eyelids. They are covered in tiny hairs, giving them a suede-like texture. If these membranes are injured, they heal very quickly. Researchers speculate this adaptation is due to the significance of flight to bats.

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