High-frequency and ultrasonic vocalizations in a subterranean rodent: the colonial tuco-tuco (Ctenomys sociabilis)

Abstract

Rodents use vocalizations in numerous behavioral contexts. The structure of these vocalizations—particularly the range of frequencies (kHz) that they encompass—reflects a combination of selective factors imposed by auditory constraints, environments, and functional contexts in which vocalizations occur. Because higher-frequency signals tend to attenuate rapidly in the underground medium, such signals are expected to be more common in subterranean rodents when conspecifics are in close proximity to one another. This suggests that social organization could influence vocal communication, with group-living species expected to use high-frequency signals more often than solitary ones. However, few comparisons of the vocal signals produced by closely related social and solitary species of subterranean rodents have been completed, thereby limiting inferences regarding the effects of social system on the vocalizations produced by these animals. As a first step toward such comparative analyses, we characterize the vocalizations of the colonial tuco-tuco (Ctenomys sociabilis), a group-living subterranean rodent from southern Argentina. Data obtained from captive members of this species indicate that colonial tuco-tucos produce high-frequency and ultrasonic (USV) vocalizations that vary markedly in structural complexity and spectral features. Production of vocalizations is affected by the sex and the spatial context of the emitter, with most vocalizations produced when males and females are in physical contact during non-aggressive encounters. In addition to suggesting that social interactions are important determinants of vocal communication in colonial tuco-tucos, our analyses provide the first evidence of ultrasonic communication within Ctenomys. The high-frequency and ultrasonic sounds produced by C. sociabilis contrast markedly with the lower frequency vocalizations emitted by members of several solitary species of tuco-tucos, offering a critical foundation for future, more detailed, phylogenetically informed comparisons of the effects of social organization on the vocal repertoires of these subterranean rodents.