IVth International Conference on Dormice (Rodentia, Gliridae)

THE VOCAL REPERTOIRE OF AN AFRICAN DORMOUSE (GRAPHIURUS PARVUS), AND COMPARISONS WITH OTHER SPECIES OF THE MYOXIDAE

Hutterer, R & Peters, G.

Zoologisches Forschungsinstitut und Museum Alexander Koenig, Adenauerallee 160, D-53113 Bonn, Germany, e-mail: r.hutterer.zfmk@uni-bonn.de

We studied the vocal repertoire of the African dormouse Graphiurus parvus (True, 1893) and compared it with what is known about vocalization in the genera Eliomys, Muscardinus, and Myoxus. Observations and sound recordings were performed in a breeding colony of Graphiurus of about 50 individuals kept in a cage (205 x 105 x 75 cm), furnished with nest boxes, tree branches and fresh twigs. Sound recordings were made with portable tape recorders UHER Report 4200 and 6000 Universal at 19 cm/s and 9.5 cm/s recording speeds and SENNHEISER MD 441, ME 80 and ME 88 directional microphones; analyses were made with a MEDAV Spektro 3000 sound spectrograph with various analysis settings. In Graphiurus parvus we were able to preliminarily distinguish 5 or 6 sound types. Until now we have refrained from naming them because we would like to avoid the use of a term already established for a vocalization of other species of the Myoxidae (or other sciurognath rodents) without evidence that phylogenetically it is the same type of vocalization in Graphiurus. It is highly likely that more sound types exist in this species than we could observe until now. A few of the sound types show a wide range of structural variability, the others are relatively stereotyped. The repertoire comprises discrete vocalization types and others that very probably belong to graded systems. Tonal, noisy or intermediate and click-like vocalizations are documented and may have frequency components in the range from about 0.3 kHz to > 20 kHz but most are limited to only a specific portion of this range. Due to the lack of appropriate recording equipment we could not check for the presence of purely ultrasonic vocalizations. Considering the fact that some vocalization types nearly cover the complete frequency range from below 0.5 kHz kHz to about 20 kHz and the species' small size, it is noteworthy that other vocalization types are largely restricted to the range below 1 kHz. All tonal vocalization types are frequency modulated, some of them with very rapid modulation. With the possible exception of one vocalization type modulation patterns in the different types documented so far are fairly stereotyped: either down-sweeps or v-shaped or inverted v-shaped. Nearly all vocalization types documented are primarily uttered serially, sometimes in rapid volleys. The majority of the vocalization types is short (< 50 ms), interval duration between the sounds in bouts can vary but can also be fairly regular and often very short (< 100 ms). Intensity of the calls, their rate of emission and/or number per calling bout seems to increase with higher motivation. It is not clear yet whether in sound types with variable tonality/noisyness tonality decreases with increasing intensity.

A tentative comparison of the sound repertoire of Graphiurus with the available information on vocalization of Eliomys, Muscardinus, and Myoxus shows that the acoustic signal repertoires of all have about the same size. Vocalizations of Graphiurus parvus differ considerably from those of the Palaearctic genera, as do the repertoires of Eliomys, Muscardinus, and Myoxus among one another. It is possible that a more comprehensive intergeneric comparison will reveal that certain genera of the Myoxidae or each of them have peculiar vocalization types.

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