Mother deer can't ID their fawns by call.

Fawns can distinguish their mom's voice from another deer's, but a mom can't pick out her fawn's call, researchers say.

That's different from recognition skills of sheep or reindeer, according to Marco Torriani of the University of Zurich in Switzerland. In past studies of those species by other research groups, the young recognized the mother's calls and vice versa.

Torriani and his colleagues recorded mother-fawn pairs of fallow deer on Swiss farms. The researchers played both a fawn's mother's call and a recording of another deer. Fawns were more likely to react to their mothers' voice by, for example, turning toward the broadcasting speaker or approaching it. When the researchers played fawn calls to the adults, however, mothers failed to react in any special manner to their own offsprings' calls.

That quirk makes sense in terms of newborn behaviors, says Torriani. Young sheep and reindeer quickly start following their mothers around with the herd, and mutual voice recognition would be a big help. Newborn fallow deer, though, hide silently in undergrowth. Mom drops by occasionally and calls. In response to her voice, the fawn steps out to feed. Thus, there may not be much advantage to mothers' recognizing her fawn's voice, the researchers say in the September American Naturalist.--S. M.