Fox Squirrels

Fox squirrels flick their tails when they can’t get a cherished nut in much the same way that humans kick a vending machine that fails to deliver the anticipated soda or candy bar, according to new UC Berkeley research.

In what is thought to be among the first studies of frustration in free-ranging animals, the findings, published online in the Journal of Comparative Psychology, suggest that animal tail movements reveal their emotional states, particularly the exasperation they feel when stymied during problem-solving tasks.

Lead author Delgado and fellow UC Berkeley researchers tracked 22 fox squirrels in their leafy habitats on the campus, putting them through a series of foraging tasks that had them puzzle their way into various open and locked containers to get to nuts or grains.

The more frustrated the squirrels became – especially if the container was locked — the more they flicked their bushy tails.