Stressed Squirrels Wig Out

Jan. 2, 2008 -- With their chattering, scampering ways, squirrels would seem to lead rather carefree lives, but a new study has found they can feel stress, and that its effects on the fluffy rodents are similar to its effects on people.

A certain amount of stress, which can cause a burst of energy, appears to improve reactions and learning ability, but too little or too much makes individuals -- both squirrels and humans -- go rather loopy.

The jittery vibe might even be the same.

"The feeling that comes with adrenaline when a cop's lights flash behind us is probably similar to the feeling a squirrel has when a hawk suddenly flies over, or when they hear an alarm call," Jill Mateo, author of the study, told Discovery News.

Mateo, an assistant professor in the University of Chicago's Department of Comparative Human Development, studied groups of Belding's ground squirrels at the Sierra Nevada Aquatic Research Laboratory. By placing cortisol in peanut butter and wheat germ treats, she artificially raised or lowered stress potentials in squirrels.

Cortisol is a hormone naturally produced by the body that raises blood pressure and blood sugar levels. Other studies indicate it provides energy to the brain, prompting the storage and retrieval of memories, Mateo said.

She focused her attention on juvenile ground squirrels. During their first month of life, they stay in cozy burrows with their mother. After this period, they go above ground and must fend for themselves.

That's when a lot of stress kicks in, and for good reason. Up to 30 percent of the young squirrels disappear during their first two weeks outside of the burrow, likely becoming dinner for hawks and other predators.

Mateo duplicated the challenges squirrels must face during this time in two ways. She put them through a maze that simulated the vegetation highways, rocks and logs that the animals would have to navigate through in the wild. She also paired the sound of a Brewer's blackbird alarm call, which warns of nearby raptors, with a Frisbee toss overhead.