MICHIGAN STATE (US) — Hyenas listen to the sound and number of intruders’ voices before deciding whether to fight or flee.
The findings, reported in the journal Animal Behavior, support the concept that living in complex social groups, like hyenas, lions, and chimpanzees do, is one of the keys to the evolution of big brains.
“They’re more cautious when they’re outnumbered and take more risks when they have the numerical advantage,” says Sarah Benson-Amram, a graduate student in zoology at Michigan State University. “Hyenas appear to be as capable as chimpanzees or lions at assessing their advantage.”
Even though spotted hyenas live in clans of up to 90 individuals, they spend much of the day in much smaller, more vulnerable groups.
When researchers played recordings of potential intruders, the hyenas’ reaction depended on how many voices they heard compared to how many fellow pack members surrounded them. Groups of three or more hyenas were far more likely to approach the source of sound than pairs or individuals.
This study is the first to show that hyenas can tell the difference between individual voices. Most of the animals in the study could distinguish up to three different voices, says Kay Holekamp, professor of zoology and BEACON researcher, whose has studied spotted hyenas in Kenya for more than 20 years.
“The recordings were taken from hyenas from other parts of Africa,” she says. “But even though the voices were unfamiliar, the hyenas in the study were able to tell when they were from the same or different animals.”
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