ITHACA, N.Y. -- Worried parents with greedy kids may now have the ultimate role model: subterranean Africa's naked mole-rats that can't wait to share newly-discovered food sources with their kin.
As reported in the November 1996 issue of Animal Behaviour (Vol. 51, pp. 957-69) by Paul W. Sherman of Cornell University and Timothy M. Judd of Colorado State University, the nearly hairless and sightless rodents would rather recruit family members to the site of food they found than eat the food themselves. The biologists watched and listened through transparent laboratory burrows as one mole-rat after another took an altruism test that many humans would fail.
In various sites in a plastic tunnel maze, the biologists had placed pea-sized bits of sweet potato. That simulated conditions in Africa, where the chisel-toothed rodents dig miles of burrows in search of the small bulbs and tubers that sustain them. Tuber patches in mole-rats' natural habitat are widely and irregularly dispersed, explained Sherman. Naked mole-rats (Heterocephalus glaber) must chew through lots of hardpan dirt to find a patch of tubers. But once they find a new source, there is usually plenty to go around.
How do mole-rat "scouts" recruit others to their newly discovered food source? That's what Sherman, a professor of animal behavior at Cornell, and Judd, a Cornell undergraduate at the time of the experiments and now a biology doctoral student in Colorado, wondered. And how do other mole rats, in colonies that average 75-80 closely-related kin, find their way through pitch-black tunnels to the newest food source?
As soon as a mole-rat scout located the biologists' stash of sweet potato bits, it would pick up one piece in its mouth and scurry directly back to the nest chamber, making a distinctive "chirp" call along the way. Once in the nest, the biologists observed, the scout would wave the food aloft in its mouth for all to smell.