Water Striders

Study says it pays to be polite

Biology News

Water Striders (Aquarius remigis). Colored spots were painted on by researchers (e.g., yellow = non-agressive red = agressive) Photo: Omar Tonsi Eldakar

A study led by Omar Tonsi Eldakar of the University of Arizona reports that groups of low-key male water striders (aka "skater bugs") participated in more matings than did groups of sexually aggressive males. In the study, which appeared in the journal Science, female striders often rejected their more persistent and aggressive suitors and instead cast a longing eye on the more easy-going beaus.

"Nice guys don't always finish last," says Eldakar, summing up his findings.

Of course, this is something the more generous among us have long preferred to believe -- but science does require an experiment.

The new study differed from earlier ones investigating the same topic in that females were able to flee unwanted suitors. Under such circumstances, the researchers found that female striders will simply depart when harassed. They prefer the company of males who give them a little breathing space.

"Individually, less aggressive males may get a smaller piece of the pie. But a group of less aggressive males has a bigger pie," says co-author John W. Pepper, "because the males don't drive away females or harass them so much they don't reproduce."

Eldakar et al. studied Aquarius remigis, a stream-dwelling strider common throughout much of North America.

He and his co-workers collected water striders from the wild during the breeding season. After evaluating the aggressiveness of each male, they placed six males and six females into each of six separate compartments dividing the surface a large tank of water.

When they observed the insects' behavior, they found that when hyper-aggressive males were present in the same chamber as less aggressive males, the hyper-aggressive jerks monopolized the females.

However, when the researchers opened gates so that the compartments were all connected, things changed. Females fled areas where they were harassed and congregated in compartments tenanted by non-aggressive males. So as a group, the meeker guys had significantly more successful matings than did their hyper-aggressive counterparts.

This all goes to show, as we thought long ago, that being an aggressive, selfish jerk doesn't always pay big dividends. As Pepper puts it, "The non-cooperator tries to get a bigger piece of the pie, but the cooperator helps the pie be bigger." And, to extend the metaphor, the larger pie ends up in the refrigerator of the milder-mannered strider.

So it seems that the meek, at least among male water striders, will have not only a great inheritance, but also a large genetic bequest -- so long as the stream where they reside happens to be compartmentalized.