Behaviour 2019
Vocal complexity predicts social bonding behavior in a monogamous rodent
Morgan L Gustison, Steven M Phelps. University of Texas at Austin, Austin, TX, United States

Prairie voles (Microtus ochrogaster) are one of the few mammals to form stable attachments, or pair bonds, between mates. A great deal is known about conspicuous behaviors in establishing these bonds, but the potential functions of inconspicuous social behaviors like ultrasonic vocalizations (USVs) remains a mystery. Here, we test the hypothesis that vocal communication is a critical part of bond formation. We paired subjects with a familiar same-sex sibling or a novel mating partner for one day while continuously tracking individuals and USVs. Specific behaviors were recorded during 10 min observations every hour. Supporting our hypothesis, mates produced higher USV rates than siblings, and mates’ vocal activity predicted subsequent social interactions like mating and reunion. USV acoustic structure differed across partner type and context. Mate USVs were more complex (e.g., long, high frequency and modulated) than the monotone USVs made by siblings, especially during courtship. Together, our results suggest that prairie voles use a complex vocal repertoire to maintain close proximity with social partners and promote mating interactions that are critical for pair-bond formation.