Ultrasonic communication in Gliridae (Rodentia): The hazel dormouse (Muscardinus avellanarius) as a case study

Ultrasonic vocalizations (USVs) have been detected in a range of small mammals, particularly rodents, and are associated not only with different social behaviours, e.g. sexual behaviour and aggression, but also with non-social behaviour in several species of mammals, including echolocation and as a by-product of respiration. Rodents in the Gliridae family are known to broadcast a variety of signals, but the behavioural relevance of the latter is poorly known. The aim of our study was to describe the vocal signals of Muscardinus avellanarius and to assess their function. By recording vocal and non-vocal behaviour of captive individuals in different social contexts, we demonstrate that M. avellanarius emits USVs and provide contextual evidence that such sounds are largely used for social communication. We identified six different vocalizations with an overall frequency range between 6.5 and 52.1 kHz, five out of six being ultrasonic (>18 kHz). The vocal repertoire in M. avellanarius was associated with social behaviours, e.g. mother-infant reunion, isolation and paired opposite-sex courtship, all activities involving individuals that are out of mutual visual contact. We therefore infer that this repertoire constitutes a medium-distance (in the range of a few metres) communication system. Further research testing different social contexts both in nature and in captivity is needed for a more complete assessment of the vocal repertoire of this species and its function.