A group of 14 females and 12 males was examined at the field research station of the University in Berkeley. The country of origin of the animals is Kenya. Over four days, the vocal repertoire of the individual clan members was first recorded in various situations, such as feeding. On the basis of this precise analysis, the individuals could be judged in their behavior in the pack. The statistical analysis considered 13 different criteria. The longest sounds of the 695 recordings lasted four seconds and included 28 notes, the shortest transmission of information took place in 200 milliseconds with two different tones.
The pitch of the laugh reveals a hyena's age. Thus, the laugh of a two-year-old animal is one third higher than that of a 20-year-old. The males generally communicate via higher tones than the females. Variations in the note frequency reveal whether a member of the clan plays a dominant or subordinate role. In the timbre, a hyena defines its individuality, which has been observed so far, especially with penguins, fur seals and seagulls.
The laughter should also be a sign of frustration and be used as a cry for help. "Lions often dispute the prey of hyenas and only a whole pack can kill several lions, " explains Theunissen. With their laughter, a single Spotted Hyena summons allies. By precisely identifying the individual, the recipient of the information immediately recognizes who is in danger. "He then decides according to the criteria of age and rank, whether he comes to the rescue or ignores the call, " explains Theunissen. displayFrédéric Theunissen (University of California, Berkeley) et al .: Online Edition BMC Ecology ddp / science.de? Rochus Rademacher