Investigating the acoustic directionality of mouse ultrasonic vocalizations

Abstract

Across the animal kingdom, ultrasonic vocalizations (USVs) are used as a means of communication, navigation, and predation, and in some species (e.g., echolocating bats and whales), the directionality of the signal facilitates these processes. The utility and characteristics of mouse USVs, however, are less clear. Using an 8-channel microphone array, we recorded, localized, and assigned USVs to individual mice that were in isolation (n = 28) or socially interacting (male-female dyads, n = 13; 4-mouse, mixed-sex groups, n = 11). Males emitted a total of 3675 (100%), 22 268 (84.48%), and 73 488 (82.05%) of the assigned vocalizations when in isolation, interacting with a female, or socializing in a group. By examining the relationship between the USV sound intensity on the eight microphones and the head directions of the mice, we observed that male mice consistently produced directional USVs across each of the three behavioral contexts. Specifically, USV intensity was strongest in the direction that the mouse was facing and weakest in the opposite direction. Overall, these findings directly demonstrate that male mouse USVs are directional and may provide insight into the communicative function of mouse vocalizations.