by D. Bruce Means
Nature can be a bit unpredictable at times. Sometimes, for instance, the diner and the main course switch places at the dinner table. Such is the strange case of the predator-prey relationship between bats and tree frogs.
In the early 1980s, biologists discovered that the fringe-lipped bat of Central America commonly caught and ate tree frogs. But I watch prey turn predator in Australia, where tree frogs literally gulp down bats.
While working on a documentary, I was filming Australian pythons nabbing bats at the mouth of Bat Cleft, a maternity cave for the little bent-wing bat (Miniopterus australis) in Mount Etna Caves National Park in southern Queensland.
Countless little bent-wing bats came spiraling out of the narrow cleft in their evening emergence. And sure enough, a dark-spotted python slipped out onto a jagged piece of limestone, then stretched out over the abyss. The little python promptly snatched one of the bats out of the air.
While watching this little drama, I paid little attention to a pair of green tree frog that also settled onto the rocks as the bats, packed tightly together, swarmed through the cleft. A bit later, I glanced down and saw, to my great surprise, the back end of a little bent-wing bat hanging out of the mouth of a frog. Frog and python sit there, inches apart, eating bats. The frog makes three gulping movements and the bat disappears.
I returned to the cleft on two more evenings and witnessed frogs eating bats a total of four times, while snakes consumed at least 30 bats. Exactly what led this population of tree frogs to add bats to its menu is uncertain. However, the destruction of alternative roosts worldwide is forcing more and more bats to congregate in fewer locations, making them increasingly vulnerable to predators.
Several of Mount Etna's bat caves have been permanently destroyed. Thanks to the diligent efforts of local colleagues and letters from BCI and its members, several, including Bat Cleft, eventually won protection.
D. BRUCE MEANS is President and Executive Director of the Coastal Plains Institute and Land Conservancy in Tallahassee, Florida, and an Adjunct Professor of Biological Science at Florida State University in Tallahassee.
(BCI members can read the whole story of the bat-eating frogs of Australia in the Winter 2003 issue of BATS magazine.)
