Fringe-lipped bats can’t be fooled by imitators of favored prey

By Susan Milius

Web edition: May 25, 2012
Print edition: June 16, 2012; Vol.181 #12 (p. 18)

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DINNERTIME

A fringe-lipped bat sweeps out of the night to carry off a túngara frog. The bat relies on a series of senses to avoid accidentally taking a poisonous meal.

Credit: Christian Ziegler

Fringe-lipped bats eat frogs even though gulping the wrong one in the dark could be fatal.

New high-speed video of the tropical bats swooping toward various frogs and toads shows that the predators deploy a sequence of senses to update their judgment of prey during an attack to avoid eating a toxic amphibian, says behavioral ecologist Rachel Page of the Smithsonian Tropical Research Institute in Gamboa, Panama. The bats proved hard to fool even when researchers played the call of a favorite edible frog while offering up another species, Page and her colleagues report in an upcoming Naturwissenschaften.

In the tropics, various bats will nab a frog if given half a chance, but only the fringe-lipped species (Trachops cirrhosus) is known to follow frog calls, such as the “tuuun chuck” call of the túngara frog (Engystomops pustulosus).

In tests in Panama, Page and her colleagues found that fringe-lipped bats turned aside in mid-air if researchers broadcast enticing túngara calls but offered up a cane toad (Rhinella marina), which is way too big for a bat to carry off.

The possibility that incoming bats might use echolocation to avoid overweight prey intrigues bat specialist Brock Fenton at the University of Western Ontario in Canada. Early studies of these bats largely ignored possible last-minute echolocation, he says.

The new tests also revealed that playing túngara calls while offering a right-sized but toxic leaf litter toad (Rhinella alata) led bats to catch and then drop the unpleasant prey. (Both bats and toads survived.)

This reaction fits with research on certain moth-hunting bats, says John M. Ratcliffe at the University of Southern Denmark. These moth specialists avoid a toxic tiger beetle when they hear its clicking noises but become much more likely to pick it up if researchers mute the clicks.