Monday, September 07, 2015

ants have group-level personality


sciencemag |  If you stuck to Aesop’s fables, you might think of all ants as the ancient storyteller described them—industrious, hard-working, and always preparing for a rainy day. But not every ant has the same personality, according to a new study. Some colonies are full of adventurous risk-takers, whereas others are less aggressive about foraging for food and exploring the great outdoors. 
Researchers say that these group “personality types” are linked to food-collecting strategies, and they could alter our understanding of how social insects behave.

Personality—consistent patterns of individual behavior—was once considered a uniquely human trait. But studies since the 1990s have shown that animals from great tits to octopuses exhibit “personality.” Even insects have personalities. Groups of cockroaches have consistently shy and bold members, whereas damselflies have shown differences in risk tolerance that stay the same from grubhood to adulthood.

To determine how group behavior might vary between ant colonies, a team of researchers led by Raphaël Boulay, an entomologist at the University of Tours in France, tested the insects in a controlled laboratory environment. They collected 27 colonies of the funnel ant (Aphaenogaster senilis) and had queens rear new workers in the lab. This meant that all ants in the experiment were young and inexperienced—a clean slate to test for personality.

The researchers then observed how each colony foraged for food and explored new environments. They counted the number of ants foraging, exploring, or hiding during set periods of time, and then compared the numbers to measure the boldness, adventurousness, and foraging efforts of each group. They also measured risk tolerance by gradually increasing the temperature of the ants’ foraging area from 26°C to 60°C. Ants that stayed out at temperatures higher than 46°C, widely considered to be the upper limit of their tolerance, were considered risk-takers.

When they reviewed their data, the scientists found strong personality differences between colonies, they reported online this month in Behavioral Ecology. Some were bold, adventurous risk-takers with highly active foragers. Others were shy, risk-averse, and fearful of new environments. Their foragers were less active, and they were less inclined to search for food at very high temperatures. When the team performed the same tests 11 weeks later, they saw that these differences persisted over time. More than half of all variation between colonies fell into distinct categories known as “behavioral syndromes.” These syndromes—similar to personality types among humans—are present across the animal kingdom and include categories like “proactive” (animals are bold, aggressive, and risk-prone) and “reactive” (animals are shy, calm, and risk-averse).