Like three-toed sloths, 50 percent of which are eaten when they leave the safety of trees to defecate on the ground, and male black widow spiders, which must tread purposefully on the webs of their female counterparts or risk being eaten, the tungara frog of Central America are forced to maintain a delicate balance between natural instinct and individual survival, the Smithsonian reported.
Like many species of frog, male tungaras attract mates by the sound of their croak, which ranges from a basic "whine" to a more complex noise accentuated by "chuks" -- added to make the call more attractive.
Following the path of many males before it (but for an entirely different reason), the tungara must expend the least amount of energy in seducing his female. If it too loudly broadcasts its seed, it arouses the attention of one of its greatest enemies, the fringe-lipped bat. Not only can the bats listen to the sound, but detect the ripples it affects in the adjoining water.
"The frogs want to call as conspiciously as they can to get mates," Rachel Page, a researcher at the Smithsonian Tropical Research Institute in Panama whose research was published today in Science.
To determine exactly how sensitive the bats are to the chucks and their ripples (and which characteristic is the better indicator of the frog's presence), Page and fellow researchers used fake frogs and either mimicked their sound's imprint in the pond or produced the sound and not the imprint. They found that bats were 37 percent more likely to attack the fake frog in the rippled condition than in the sound condition.
"Very unusual," Page said "This is the only species of bat in the world known to eavesdrop on the calls of frogs."
That's not all they're capable of. According to the Smithsonian, the bat species is also able to decipher the poisonout nature of a frog simply based on its sound.
In turn, the tungara frogs are aware they're being monitored.
"When they see approaching bats, the first thing they do is stop calling," Page said. "Then they deflate their vocal sack, hunch over into the water and swim away."
