The vocalisations of the spotted hyena are used to communicate in complex ways.
Credit: Nicholas Mathevon
OREGON, U.S.: The high-pitched, maniacal 'laugh' of the hyena is not used by all individuals equally, but mostly by subordinates as a sign of frustration.
"The hyena's laugh is a multi-informative signal," said Nicholas Mathevon, a biologist at the University of Jean Monnet, in Saint-Etienne, France, who studied captive hyenas, recording their laughs and subjecting them to sophisticated acoustical studies.
The hyena has up to 20 vocalisation types, but only two had previously been studied. One is a 'whoop', used as a long-distance call, while the other is a groan, used for communication over short ranges.
Complex social structure
Mathevon found that the laugh tends to occur when subordinate animals are attacked or chased away by dominant hyenas during feeding times and "is mainly emitted when [the animal] is frustrated," said Mathevon, who presented his results this week at the Acoustics Society of America's annual conference in Portland, Oregon.
The spotted hyena (Crocuta crocuta), which is found widely across Africa, has a complex social structure – as complex as the social systems of primates such as baboons and macaques. It is a savage hierarchy; subordinates are frequently attacked and denied access to food and mates.
"What is cool about hyenas is that they have a very special social system. This hierarchy is very, very strong. So you have a lot of different communication signals that are used to stabilise this hierarchy," Mathevon said. They're also nocturnal, so with reduced visual cues, vocalisations are an important form of communication, he added.
Laugh may draw predators
Mathevon's studies revealed not only that the call is a sign of frustration, but also that it is predominantly emitted by low-status, subordinate animals.
What has puzzled scientists is that the 'laugh' is so loud. Such a loud vocalisation would attract other hyenas, increasing the strength of the pack and thus reducing the animal's food supply further.
But, it might also draw other predators, such as lions, to steal food.
Perhaps, Mathevon speculated, this means that dominant animals are forced to keep them quiet by allowing them to eat so that larger predators aren't drawn to sounds that signal mealtimes.
Other researchers are impressed by the findings. "It's great," said Sharon Glaeser, a biologist at Portland State University in Oregon, who is doing similar work with elephants.
"What it tells you is that they're a social species that uses [vocalisation] as part of their social structure. We [humans] sound different to each other and we can tell the state of mind that one of our friends is in. Maybe that's part of what they [hyenas] are doing."
The Hyaena's "laugh"
Try actually taking a minute and listening to one of the most beautiful creatures on earth. Listen to the sound, the inflections, all of it. Don't try and compare it to the sounds a primate might make. Why try to compare them to some other living animal. They are what they are, respect and appreciate them for it. They will never lie to you, they will always be what they are. You want one moment of "perfect beauty", watch one for a while.
jim@vorloncat.com