Ultrasonic vocalizations of infant short-tailed field voles, Microtus Agrestis

Marie-Juliette Mandelli and Gillian Sales*

Institute of Neuroinformatics, University of Zurich, and ETHZ, Winterthurerstr. 190, 8057 Zurich, Switzerland (MJM)
*King’s College London, Division of Life Sciences, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NN, United Kingdom (GS)

Ultrasonic vocalizations of infant rodents are used in developmental studies for investigating the effects of drugs or environmental pollutants. Few studies, however, have analyzed the frequency characteristics of these ultrasonic vocalizations. The present work investigates the physical and vocal development of infants (1-14 days of age) of the short-tailed field vole (field vole), Microtus agrestis, under 2 different conditions of isolation: (1) immediately after being isolated from the nest or (2) after 10 min of isolation. Seventy three percent of the infants vocalized and there was great variation among calling infants in the number of vocalizations emitted. More infants, especially males, called during the second period of isolation than during the first and latency to call increased with age in males. The ultrasonic vocalizations were comparable to those recorded from North American voles. They were classified into 7 categories based on characteristics of the fundamental frequency. Simple calls were emitted most commonly and became more frequent in older infants, whereas the proportion of calls with a down-sweep in frequency and audible clicks decreased with age. The emission of ultrasonic calls therefore appears to reflect changes both in physical development of the infants and in their external environment.

Journal of Mammalogy, Volume 85 (2004) , Issue 2, pp. 282–289.