A comparative study of isolation-induced ultrasonic vocalization in rodent pups.

The purpose of this study was to determine whether species differences in neonatal vocalizations of rodent pups could be observed. Ultrasonic vocalizations of pups of 5 rodent species, mouse (ICR), vole (Microtus arvalis), Syrian hamster, rat (Wistar-Imamichi), and Mongolian gerbil were recorded from 3 to 15 or 21 days of age. Recordings were made under conditions of separation from mothers and litter mates in a cooled chamber (approximately 10 degrees C). The major species differences observed were age specific and species specific frequencies. The Mongolian gerbil displayed a different frequency change with age. Namely, the day on which ultrasonic vocalizations ceased was delayed in Mongolian gerbil compared with the other rodents. The modal peak frequencies of ultrasound emitted from pups at 3 days of age were low (around 35 kHz) in the vole and the Syrian hamster, medium (around 45 kHz) in the rat and the Mongolian gerbil, and high (around 55 kHz) in the mouse.