A comparison of prairie vole audible and ultrasonic pup calls and attraction to them by adults of each sex

Rodent pups of many species emit both ultrasonic vocalizations (USVs) and calls spanning into a lower frequency range, audible to humans (AUDs), yet there has been little systematic comparison of these different call types, or analyses of how they might differ in signal function. Here the spectral and temporal characteristics of USV and AUD pup calls are described for the prairie vole (Microtus ochrogaster), a model used in studies of monogamous mating and biparental care, and a species with an unusually large functional and anatomical representation of auditory cortex. Findings provide a detailed description of each call type, including changes to a number of USV characteristics over pup development. Adult attraction to the playback of these two call types was tested in groups that differed in regards to sex and reproductive status. Separate groups included virgins as well as paired animals of each sex, tested at time points either prior to the birth of pups (associated with either mid or late gestation), or at postpartum time points (parents of 2-3 day olds and parents of 8-9 day olds). Adults were attracted to both USVs and AUDs, but group differences were found only in the attraction to USVs. Males were more attracted to USVs than females, and there were interactions of sex and reproductive status. Results suggest that pup vocal communication is quite sophisticated, and that USVs and AUDs may have different communicative functions.