Nature

07
Aug

Ant Colonies Have More Than Just a Collective Purpose. They Have Collective Personalities, Too

We may be familiar with ants, but when it comes to their social system, we’re worlds apart. Eusocial by nature—they have a queen who breeds; others care for the young—ants have something of a collective mind. And, it turns out, something of a collective personality.

We know certain behaviors, like foraging distance, vary between insect colonies. And we know that individual insects in those colonies can have personalities. Social spiders, for example, take on different roles in the colony, such as warrior or nanny, depending on their aggressiveness or docility. But Sarah Bengston, a researcher at the University of Arizona, discovered something bigger at play when she studied ant behavior on the colony level. Behaviors tended to group together, and something different started to emerge: a colony personality.

Temnothorax-rugatulus
A nest of Temnothorax rugatulus in Arizona

Bengston studied rock ant colonies in the western United States, going as far north as Washington and as far south as Arizona. She measured their foraging behavior—how far would they go for food, and how hard did they work to get it?—and whether they fought or fled when their nest was attacked. Aggressive behavior can be measured in the lab, but foraging behavior can’t—so Bengston had to get right down to the forest floor.

Jonathan Webb, writing for BBC News:

To gather this data, Ms. Bengston followed thousands of ants in the great outdoors, mostly in pine and juniper forests. She tagged them with pink fluorescent powder and chased them through the leaf matter on her hands and knees.

“I’ve done an awful lot of crawling,” she told the BBC. “It can get a little tedious but it’s also a lot of fun, because you get to see a lot of natural behaviours that we wouldn’t necessarily see in the lab.

“I spend a lot of time looking slightly like a crazy person on the side of hiking trails.”

She found that the ant colonies that were willing to roam farther for food were also more aggressive towards invaders. Other colonies stayed closer to home, focusing their efforts on collecting resources nearby. This distinction between bold colonies and shy colonies reflected their location: The aggressive, swashbuckling colonies lived farther north than their shyer cousins.

Northern ants may be bolder, Bengston says, because once the snow finally melts in the spring, they only have a narrow window of time to reproduce before winter descends again.

Bengston’s study raises questions about whether colonies of other eusocial animals—like bees, termites, and mole rats—might have environmentally-influenced personalities, too. Perhaps colonies in unforgiving climates are like the Vikings of the animal kingdom: willing, even eager, to roam far and wide to conquer new territory and feed their kin before the ice closes in.