Hyenas' laughter signals decoded

Washington, March 30 (ANI): The giggling sounds of a hyena contain important information about the animal's age, dominance and identity, scientists have found.

In the study, researchers recorded the calls of 26 hyenas in captivity and found that variations in the giggles' pitch and timbre help hyenas to establish social hierarchies.

Frederic Theunissen, from the University of California at Berkeley, USA, and Nicolas Mathevon, from the Universite Jean Monnet, St. Etienne, France worked with a team of researchers to study the animals in a field station at Berkeley.

"The hyena's laugh gives receivers cues to assess the social rank of the emitting individual. This may allow hyenas to establish feeding rights and organize their food-gathering activities," Theunissen said.

The researchers found that while the pitch of the giggle reveals a hyena's age, variations in the frequency of notes can encode information about dominant and subordinate status.

These vocalizations are mainly produced during food contests by animals that are prevented from securing access to a kill, and have been considered a gesture of submission.

Theunissen and colleagues also suggest that the giggle may be a sign of frustration and that it may be intended to summon help.

"Lions often eat prey previously killed by hyenas. A solitary hyena has no chance when confronted by a lion, whereas a hyena group often can 'mob' one or two lions and get their food back. Giggles could therefore allow the recruitment of allies," he said.

"Cooperation and competition are everyday components of a hyena's life. When hearing a giggling individual, clan-mate hyenas could receive information about who is getting frustrated (in terms of individual identity, age, status) and decide to join the giggler, or conversely to ignore it or move away," he added.

The researchers plan to further test these hypotheses with playback experiments in the field.

The study appears in the open access journal BMC Ecology. (ANI)