Ask a Scientist

Do bats really sleep upside down?

CorrespondentOctober 28, 2012 

Here are a couple options for shots of Lisa Gatens to go with John Bordsen’s Sci-Tech “Ask A Naturalist” column – I believe it’s for Oct 29. I might be able to get you a higher res version of the “mug” if that’s the one you want go with. The other shows Lisa grappling with a red bat in Georgia though – so maybe more appropriate. Lisa may have sent this one to Marla already.

Lisa Gatens is the curator of mammals at the N.C. Museum of Natural Sciences. Here she explains some little-known facts about bats. Questions and answers have been edited.

Q: Do bats actually sleep upside down, and if so, why?

They do, because hanging upside down, either during the day or while they sleep, is an adaptation for flight. Though some species can maneuver about quite well on the ground, and even take flight, most species release the grasp they have with Velcro-like claws that securely hold them to any roost, and drop in order to take flight.

Q: What do bats eat? Do vampire bats really suck blood?

Bats are extremely diverse, both in terms of numbers of species, as well as where and how they live. In tropical and subtropical regions, plant-feeding specialists are adapted to feed on fruits, nectar or pollen. There are others adapted to feed on fish, frogs, mice and scorpions! The three species of vampire bats, which occur only in Mexico, Central America and northern South America, do feed exclusively on the blood of vertebrates. They do not puncture and suck, like vampires in movies or on television, but rather slice with very sharp incisors and then lap the free-flowing blood. However, 70 percent of all bats eat insects.

Q: Why are bats nocturnal?

Though Old World fruit bats are diurnal (active during the day), the vast majority of bats worldwide are nocturnal. Although there are many daytime predators of insects, there are few predators of nighttime insects. With their incredibly precise echolocation (the use of sound to locate objects in their environment) and maneuverability in flight, bats have a predatory ability far beyond what is seen in insectivorous birds and have found their niche in nighttime feeds.

Q: What are some little-known facts about bats?

Vampire bats live off the blood of warm-blooded animals, and there are important medical implications in the way they feed. The saliva of vampire bats contains anticoagulants – chemicals that prevent blood from clotting. Currently, a drug to treat stroke victims is being tested. This drug was developed from a compound in vampire bat saliva.

In the tropics, plant-feeding bats play a crucial role in seed dispersal and pollination. Many tropical fruits that are consumed in the United States and worldwide are from bat-dispersed seeds: bananas, plantains, mangoes, avocados, tamarind, figs, dates and others. And, bats play an important role in pollination of night-blooming plants.

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