U. California-Berkeley researchers studying hyena communication recently found that the giggles the animals produce are no laughing matter.
The study, published March 30 in the open-access journal BMC Ecology, analyzes the different giggles of spotted hyenas as they relate to age, identity and social status, according to UC Berkeley researcher and co-author of the study Frederic Theunissen.
The study focused on the hyenas’ giggles, which occur in moments of stress or conflict, Theunissen said, such as when a hyena is fighting for possession of a kill. However, rather than representing an involuntary noise, the study revealed that the notorious hyena giggle is a highly complex social tool and is an indication of social status.
“The social status was a little bit of a surprise,” Theunissen said. “It’s a society where you need both competition and collaboration, and so to manage that type of society you need a complex way to communicate.”
Theunissen and his colleagues observed a colony of hyenas at the Berkeley Field Station for Behavioral Research, located among 29 acres in the hills above the UC Berkeley campus. In this controlled environment, the researchers put two hyenas, one dominant and one subordinate, in an enclosed space and recorded the ensuing giggles.
The pitch of a subordinate animal’s giggle varies more than that of a dominant hyena, according to the study. As a hyena becomes older, the frequency of its giggle lowers, the study stated.
Steve Glickman, a co-author of the study and a professor of psychology at UC Berkeley, said the results of the preliminary study should reflect the interactions of hyenas in the wild.
“Vocalizations appear to be elicited by the same kinds of situations in which they would occur in nature,” he said in an e-mail. “We work very closely with field biologists engaged in the study of spotted hyenas in nature in order to insure the ecological validity of our work.”
While the basic interactions between hyenas do not change in captivity, Kay Holekamp, hyena expert and professor of zoology at Michigan State University, said the complex group dynamic of a hyena colony in the wild will give an added dimension to the results.
Holekamp said in a colony of 70 hyenas, each one has both subordinate and dominant status depending on the hyena with which they are communicating.
If he secures funding, Theunissen said he hopes to further his study of the spotted hyena in Kenya, where Holekamp conducts her field work.
“Frederic will be able to figure out whether they change their tune when they are actually talking to a dominant versus subordinate, which will be a really interesting finding,” Holekamp said.
According to Holekamp, this study is the first that has analyzed hyena giggles specifically rather than other types of vocalization.
“The finding that these giggles are unique is actually quite important, because the giggle is why they’re called laughing hyenas,” she said. “People have done a little bit of work on other hyena vocalizations, but these animals have a very complicated vocal repertoire.”
Holekamp said that of the 275 species of the order of carnivora, spotted hyenas have the most complicated society.
“Spotted hyenas are wonderful animals that need to be appreciated and protected in nature,” Glickman said in an e-mail. “They have an undeserved reputation as ugly, disgusting animals.”