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. Dr. Warkentin and Kristina L. Cohen, a Ph.D. student in Dr. Warkentin’s lab, and Marc. A. Seid, a biologist at the University of Scranton, conducted a number of tests on embryos to determine how they manage early hatching. They published their results in The Journal of Experimental Biology. Dr. Warkentin said she didn’t know of other frogs with that speed of hatching, and that it was extraordinary to think that an embryo could have this defensive ability. “It can save its own life,” she said.