Big Food Makes Squirrels More Vigilant

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July 13, 2007 — Giving a squirrel a big, sweet cookie can be a kind gesture, and now scientists have found it also encourages the critter to watch for predators. The conclusion, in a newly published study, has implications for other species, including the survival of those facing human-caused changes to their habitats.

Most animals have two daily concerns: Getting food and not becoming food. Unfortunately, concentrating on one of those activities is almost always at the cost of the other.

"These two things make you survive," said animal behavior researcher Joanna Makowska at the University of British Columbia and lead author of a paper on an experiment that revealed how squirrels juggle those needs in the July issue of Animal Behaviour.

"Most animals can’t be very vigilant while eating," Makowska told Discovery News.

To get a clearer picture of just how and when squirrels choose to focus on food or predators, she and her undergraduate professor at McGill University, Donald Kramer, created an experiment that put the squirrels to the test. They placed sunflower seeds inside a two-and-a-half-foot high frame that blocked their peripheral views of the urban park in which they lived.

The idea was to force the squirrels to choose between eating and hopping out of the frame to watch for dogs, foxes and other predators.

"The squirrels never left," said Makowska. "They just ate them all. We thought this was strange."

So Makowska suggested they try giving the squirrels something that took more than a few seconds to eat, like soda crackers with peanut butter, which takes about three minutes for a squirrel to finish off.

"Lo and behold: When they ate the peanut butter crackers they moved out of the frame," said Makowska. "That confirmed to us that they valued being vigilant" even when they were eating, when the food makes it possible.

"By setting up this little test, we got them to tell us ‘Is the view important while you’re eating?’" said Kramer. "With a big food item it seems like it’s worth it to re-position."

The matter is important beyond squirrels because so many animals have to make the same choice in one way or another. And, as habitats change, their choices may or may not help them survive, explained animal behavior researcher Peter Bednekoff of Eastern Michigan University.

"We expect this to apply to birds as well," said Bednekoff, although wild birds are harder to study with the same experimental approach because they can fly away with their food.

"Some of the potential practical areas are in understanding (an animal’s) misperception of human-altered habitat," said Bednekoff.

For instance, some changes in habitat might mislead animals to think they are safer when they are not, or in danger when they are not. A good example of the former situation is the plight of many native animals in New Zealand and Australia. These critters are unused to predators and now face a threat from housecats.

There’s also just the way the lay of the land changes — and hence the view — with human activities, Bednekoff said. "We tend to really open things up or let things get really brushy."

All of this can have big impacts on the way animals behave — either exposing them to predators or wasting their energy with unnecessary vigilance.

It may also be important to consider that eyesight is not the only factor involved in the vigilance and eating equation, Bednekoff said. There are also sound and scents.

"One of the things we’ve wondered about is how much eating interferes with hearing," Bednekoff told Discovery News. It may be equally important for squirrels and other prey to stop chewing every now and then to listen and sniff the air, regardless of the view.