Babies of the red-eyed tree frog (Agalychnis callidryas) have a super-speedy getaway technique to escape predators before they’re born.
Frog egg hatching is usually a rather slow process. Enzymes are released to break down the jelly that coats the eggs, and that normally takes hours. But the red-eyed tree frog tadpoles can also hatch in seconds - if needed.
A graduate student Kristina Cohen filmed the tadpoles in action using a high-speed video camera, to figure out how they achieve this feat.
In a paper in the Journal of Experimental Biology Cohen explains how the tadpoles make their quick getaway. From slowed footage she noticed the baby frogs created a hole in their egg without touching the membrane, but shaking within the egg. Turns out they stockpile the membrane-dissolving fluid in their snouts and can release it rapidly when in danger. Then, as fluid leaks from a part of the egg in front of the embryo’s face, it then launches at the ruptured spot to wriggle through – to freedom.
The escape maneuver was first described in a study from 1995 by Karen Warkentin. Her research showed that there was a “trade-off” between predator risks before and after hatching. Her research paper observed that eggs hatched at different rates depending on whether they were under attack or not.
Plasticity in the red-tree frog’s eggs allows tadpoles to analyse their risk of survival and if need be they can instantaneously hatch and drop into the water if they were under predator attack.
The study shows that the tadpoles survive aerial attacks 80 per cent of the time. Warkentin used her observation to explain why the tadpoles escaped, but didn’t have a conclusion as to how. Now Cohen has found the answer with the help of her footage.
“They could do it in six seconds,” Cohen told National Geographic, “we’ve recorded them getting out in less than that,” in other experiments too. The snake might get a mouthful of their siblings, but only just.