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Oct. 25, 2011

The Flight of the Bumblebee Bat

by Kara Rogers

In the dark depths of a limestone cave in Sai Yok National Park, a tiny bat hangs effortlessly from the ceiling, resting, waiting for sunset, when it will take flight and embark on its nightly foraging expedition. It will not be out for long -- indeed, this bat, the bumblebee bat (Craseonycteris thonglongyai), needs only a few small insects to satisfy its appetite. It is, after all, a mere two grams in weight and a little over an inch in length, making it one of the world's smallest mammals.

The bumblebee bat is also known as the hog-nosed bat or Old World hog-nosed bat. Both names reflect the bat's other distinguishing trait, a fleshy pig-like snout. The “Old World” name also alludes to the part of the world it inhabits. Its true range in the Old World, however, extends only from southern Myanmar to west-central Thailand, which is the site of Sai Yok park.

Within its range, the bumblebee bat spends much of its time hidden in limestone caves along rivers on the edges of bamboo and deciduous forests. Its red-brown to gray color helps it blend seamlessly into the background of its cave habitat. It flies only under the cover of darkness in the dense forests, where it is but a fleeting shadow in the night. Such secretive behavior would suggest that bumblebee bats are avoiding predators. But exactly what predators the bats are evading remains unknown.

In fact, there is much about the bumblebee bat that has yet to be described. For example, little is known about their reproductive behavior and whether colonies move from one cave to another. What is known, is that like most other types of bats, the bumblebee bat navigates and locates prey by emitting high-pitched sounds that bounce off objects and reflect back to its ears. This process, known as echolocation, provides the bat with different types of information, such as variations in loudness, time delay from when a pulse of sound was emitted and returned, and time differences in the return of sound to the two ears. From this information, they are able to detect the precise location, orientation, and type of prey they encounter.

The bumblebee bat's remote cave sites would suggest that the species is safe from potentially threatening human activities. But since its discovery in the 1970s by Thai mammologist Kitti Thonglongya (for whom it is sometimes referred to as Kitti's hog-nosed bat), the species has been in decline. According to the IUCN Red List of Threatened Species, colonies at some cave sites decreased by 10 percent between 1983 and 1997 and by an estimated 14 percent between 1998 and 2008. In fact, there are now fewer than 10,000 bumblebee bats left in the wild, and populations in Thailand are expected to decrease by another 10 percent in the next decade.

Major threats to the existence of the bumblebee bat stem from human activities and include, for example, human intrusion into caves from tourism and religious pilgrimages and habitat destruction from mining and the burning of forests around cave entrances. Many of these activities suggest that people are unaware of the bat's presence or the impact of their own presence. So, as part of efforts to save the tiny creature, conservationists must now work to improve public education and awareness. Along with scientific study, education and awareness will better equip the public and scientists with the knowledge they need to ensure the bumblebee bat's protection.
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Kara Rogers is a freelance science writer and senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is a member of the National Association of Science Writers and author of Science Up Front on the Britannica Blog. She holds a Ph.D. in Pharmacology/Toxicology, but enjoys reading and writing about all things science. You can follow her on Twitter at @karaerogers.

This post also appears on the Britannica Blog.

About Kara Rogers

Kara is a freelance science writer and senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is the author of Out of Nature: Why Drugs From Plants Matter to the Future of Humanity (University of Arizona Press, 2012).

The views expressed are those of the author and are not necessarily those of Science Friday.

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