Coquí frogs got smaller, squeakier as climate warmed

Climate change might also mean a bit of frog-call change.

Male coquí frogs (Eleutherodactylus coqui) along a mountain slope in Puerto Rico have increased the pitch of their “coquí” calls a bit and shortened their chirps compared with frogs at the same altitudes 23 years earlier. Peter Narins and Sebastian Meenderink of UCLA report the finding April 9 in Proceedings of the Royal Society B.

Warming temperatures tend to nudge animals toward smaller bodies. And smaller body sizes in frogs often means their voices head toward the soprano rather than the bass.

Narins and students recorded coquí calls in 1983 and 1984 along a 13-kilometer stretch up the side of El Yunque mountain. Calls ranged from quicker and higher pitched in the lowlands to longer and lower near the peak.

Narins returned in 2006 with Meenderink, recording 116 male frogs on the same slope. This pair found the whole gradient shifted upward. Frogs sounded the “qui” part of their call, for example, at a pitch comparable to that of counterparts that lived 83 meters downslope decades earlier. Based on the shifts, the researchers hypothesized an amount of warming in Puerto Rico that matched the uptick of 0.37 degree Celsius recorded at weather stations.