RESEARCH ARTICLE Open Access What the hyena’s laugh tells: Sex, age, dominance and individual signature in the giggling call of Crocuta crocuta Nicolas Mathevon 1,2† , Aaron Koralek 3 , Mary Weldele 4,5 , Stephen E Glickman 4,5 , Frédéric E Theunissen 3,4*† Abstract Background: Among mammals living in social groups, individuals form communication networks where they signal their identity and social status, facilitating social interaction. In spite of its importance for understanding of mammalian societies, the coding of individual-related information in the vocal signals of non-primate mammals has been relatively neglected. The present study focuses on the spotted hyena Crocuta crocuta, a social carnivore known for its complex female-dominated society. We investigate if and how the well-known hyena’s laugh, also known as the giggle call, encodes information about the emitter. Results: By analyzing acoustic structure in both temporal and frequency domains, we show that the hyena’s laugh can encode information about age, individual identity and dominant/subordinate status, providing cues to receivers that could enable assessment of the social position of an emitting individual. Conclusions: The range of messages encoded in the hyena’s laugh is likely to play a role during social interactions. This call, together with other vocalizations and other sensory channels, should ensure an array of communication signals that support the complex social system of the spotted hyena. Experimental studies are now needed to decipher precisely the communication network of this species. Background The origin and maintenance of social group structure is a topic of central concern in vertebrate biology [1-4]. Whereas one approach is to understand the processes that can account for sociality over an evolutionary scale [5-8], a proximal point of view aims to decipher the mechanisms by which the social structure of a group is maintained -or not- over an individual lifetime scale [9-13]. Since Darwin’s book on the expression of emo- tion [14] and followed by numerous studies in the field, it is well known that information on social status can help individuals adjust their behaviour, for example by avoiding useless fights and polishing social interactions [15-17]. Chemical, visual and acoustic signals have been shown to encode information about sex, kinship, indivi- dual identity, morphological cues, as well as motiva- tional and physiological states of the sender [18-28]. As some of these cues can potentially be correlated to fight- ing ability and dominance rank, the information helps congeners evaluate the emitter’ s social position within the group [18,29-38]. We extended these studies by examining the information that is present in one of the acoustic communication signals of a unique social carni- vore, the spotted hyena Crocuta crocuta. Spotted hyenas are nocturnal social carnivores, typically living in multi- male, multi-female, “ clans ” of 10 - 90 individuals. Spotted hyenas are efficient hunters. A lone hyena is capable of capturing prey as large as a wildebeest. Hye- nas will also hunt collaboratively, for example to catch zebras [39]. But both sole and collaborative hunting can generate intense competition as clan mates will con- verge on the carcass. Spotted hyenas have a matrilineal social system similar to that of many old world primates [40]. Within spotted hyena clans, there are separate male and female dominance hierarchies, but all females, and their sub-adult offspring, totally dominate all adult immigrant males. Such female dominance persists in the captive colony at the University of California, Berkeley, * Correspondence: theunissen@berkeley.edu † Contributed equally 3 University of California at Berkeley, Helen Wills Neuroscience Institute, Berkeley, USA Mathevon et al. BMC Ecology 2010, 10:9 http://www.biomedcentral.com/1472-6785/10/9 © 2010 Mathevon et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.