On the horizon: news from the frontiers of science
Scientists forecast solar outbursts, why ants are selfless road workers, and how farmers can benefit birds.
from the May 31, 2007 edition
Page 2 of 3
Ants: selfless road workers
Army ants have evolved an effective way to patch potholes in their paths: They pile into the gap to smooth the way for their comrades.
That's the story two University of Bristol researchers tell after studying army ants (Eciton burchellii) from the rain forests of Central and South America. The ants – up to 200,000 at a time – sally forth to raid their surroundings for food. The ants form an unbroken stream between the vanguard and the nest back home. Foraging ants scurry back along the trail with prey they've captured. But when the homeward-bound ants approach a gap in the ground cover, other ants fill it in until the path is smooth. This hastens the return of food to the nest. Once the food-bearing ants pass, the living pothole patch leaves the gap and heads home, too.
The duo tested the process in the lab using wood containing holes of different sizes. If the holes were small enough for one ant to span, the ant whose size best matched the hole emerged to bridge it. If the hole was too large for any one ant, enough would come forward to fill it and smooth the way. The behavior allows far more food to reach the nests than would otherwise be the case; thus, the living pothole patches more than compensate for the fact that they don't carry prey themselves.
"When it comes to ants, they have their own do-it-yourself highways agency," says Nigel Franks, one of the two researchers. The study appears in the June issue of the journal Animal Behaviour.
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