Gannets avoid neighbors

A northern gannet (By Liam Quinn via Wikimedia Commons)

Few who have seen a northern gannet aggressively plunge headfirst into the ocean after a shoal of fish would think there is anything polite about this bird’s eating habits. But it turns out that gannets, large ivory-hued seabirds with heads the color of a toasted marshmallow and pike-like beaks, don’t hone in on neighboring colonies’ territories when they are out hunting, according to a paper published today in Science. What’s more, the study’s authors believe that gannets aren’t alone in acting this way.

Some animals that live in colonies, such as the infamous fire ant, use brute force to keep interlopers off their feeding grounds. Gannets, however, do not enforce their boundaries, but rather stick to their own colony’s domain voluntarily. Their behavior challenges the widely-held view that less aggressive animals overlap with neighboring colonies when they forage.

To better understand the birds’ foraging behavior, a team led by scientists from the University of Leeds and the University of Exeter used satellites to track almost 200 gannets from 12 colonies abutting the British Isles. They found that gannets from nearby groups foraged in areas that rarely overlapped, traveling away from their neighbors to find food.

The gannets aren’t following this maritime etiquette for the sake of civility, of course. Gannets that live close to each other may hunt together when their territories overlap a little, but as prey becomes scarcer, the birds spread out. After all, there is no point in trying to go after a shoal that birds from another colony already plundered. And the more gannets that are in the picture, the more crystallized this division becomes.

The boundaries solidify over time as gannets within a colony unintentionally teach others where to forage—and which locations are off limits. Before heading out to sea, the birds congregate on the water near their colony and then leave in groups. Less savvy birds can then learn from their more successful peers where to go to avoid competition with other groups.

But are gannets the only species to limit competition for food this way? The study’s authors believe that other animals such as seals, bats, and bumblebees may behave in a similar fashion. If so, it could be time for scientists to reevaluate what we know about how animal colonies track down lunch.