Paper wasps: Small brains, big memories

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ANN ARBOR, Mich., Sept. 24 (UPI) -- A U.S. study finds paper wasps, with brains less than a millionth the size of a human's brain, can remember individual wasps for at least a week.

University of Michigan graduate student Michael Sheehan and Assistant Professor Elizabeth Tibbetts showed memory prevailed even after the wasps met and interacted with many other wasps.

In the study, Sheehan measured aggression between 50 wasp queens in four different encounters during eight days. On the first day, two wasps that never had met were placed in an observation chamber for a day and their initial interactions videotaped. Then the pair was separated, and each wasp was put in a communal cage with 10 other wasps. A week later, the pair met again, and again their behavior was videotaped.

When the researchers analyzed the videotapes, scoring the wasps' social interactions on a scale of zero for no aggression to four for all-out grappling, they found the wasps treated each other better during their second encounter, suggesting they remembered each other.

The scientists say their finding suggests wasps' social interactions are based on memories of past encounters, rather than on rote adherence to simple rules.

The research appears in the journal Current Biology.