BIOLOGY Altruistic behavior is common in the animal kingdom, but seldom do individuals go so far as to risk their own lives to save another. Recently, however, biologists at Mount Holyoke College and the University of Paris 13 observed just such a sacrifice among lab specimens of Cataglyphis cursor, a species of desert ant native to France.

To further investigate the unusual behavior, the researchers plucked an ant from its nest and tied it down with a thread before half-burying it in sand in view of its nestmates. The ants chewed through the thread and dug the sand away from the trapped insect, freeing it at the risk of becoming entangled or buried themselves.

The researchers later found that some species of ants rescue their nestmates, and others just look out for themselves. The findings could shed light on the evolutionary basis of rescue behavior.