It’s a good thing for frog embryos to be able to hatch early. Suppose there’s a drought or some other environmental change that means the growing tadpoles would be better off in the water than in the egg.

The timing of hatching is subject to cues from the environment for many species, but even among these flexible hatchers the red-eyed treefrog stands out. It can escape its egg in seconds if threatened by a predator.

The frogs normally lay a mass of 40 or so eggs on a twig or leaf over a freshwater pond. If all is well, the eggs hatch at 6 or 7 days old and the tadpoles fall into the pond.

But if the eggs are attacked by a snake or a wasp during the last couple of days of development, the embryos can launch early. They wriggle out and drop to the water in less than a minute, sometimes in less than 10 seconds.