Hyenas Baby Talk With Groans

July 7, 2008 -- Spotted hyenas are well known for their laughs, but scientists have just determined that the carnivores communicate with their cubs using the hyena version of baby talk: melodic groans.

The find highlights what a complicated vocal repertoire these very social animals possess. In addition to the laughing, each hyena has its own "whoop" sound that identifies individuals, so "whoop" in hyena speak is somewhat equivalent to a person yelling out his or her name.

"Their lifestyle requires recognizing individuals within their social groups and adjusting their behavior accordingly," co-author Steve Glickman told Discovery News.

"Communication is central to complex, flexible social organization," Glickman, a professor of psychology and integrative biology at the University of California at Berkeley, added.

For the study, presented at the Acoustics08 conference in Paris last week, Glickman and his colleagues focused on hyena groans. To elicit the sounds, the researchers presented hyenas at the Berkeley Field Station for Behavioral Research with three things: meaty bones, unfamiliar spotted hyena cubs and an empty transport cage used to contain bones or cubs during other experiments.

The adults groaned more at the cubs than the objects, with cub groans sounding much more melodic and gentle. When the animals groaned at the bones and the cage, the vocalizations were less tonal and had a lower identified frequency.

Glickman said the exact meaning behind the song-like groaning to cubs remains unknown, but in the wild "groans are used by females to call their cubs from underground burrows."

Surprisingly, to human ears, the male sounds were always higher in pitch than those made by females.

"Among spotted hyenas, females are, on average, larger than males and the deeper fundamental frequencies may simply be a function of body size," he explained.