U-M researchers have demonstrated for the first time that stress hormones are responsible for altering the body shape of developing animals, so they are better equipped to survive predator attacks.

Through a series of experiments conducted at field sites and in the laboratory,  researchers demonstrated that prolonged exposure to a stress hormone enabled tadpoles to increase the size of their tails, which improved their ability to avoid lethal predator attacks by swimming away faster.

“This is the first clear demonstration that a stress hormone produced by the animal can actually cause a morphological change, a change in body shape that improves their survival in the presence of lethal predators. It's a survival response," said Professor Bob Denver.

First author of the paper is Jessica Middlemis Maher, a recent EEB doctoral graduate who is now at Michigan State University, with coauthors Professors Denver and Earl Werner. The team's surprising findings are detailed in a paper published online March 5, 2013 in the journal Proceedings of the Royal Society B. Middlemis Maher conducted the work for her dissertation. Werner is director of the E.S. George Reserve in Pinckney, Mich., northwest of Ann Arbor where tadpoles were collected from ponds.

The paper is being widely covered in the media, including this Los Angeles Times article and in the Spanish language media.

U-M News Service press release

Watch for an EEB research feature coming soon

Captions: (top) A wood frog tadpole with a normal size tail. (bottom)  In response to prolonged exposure to the threat of predator attacks, this wood frog tadpole increased the height of its tail, which makes it better equipped to survive such attacks. Image credit: Michael Benard