Leptin promotes social context-specific increase in advertisement song effort of male Alston's singing mice

Animal display behaviors, such as advertisement songs, are flashy and attention grabbing by necessity. In order to balance the costs and benefits of such signals, individuals must be able to assess both their own energetic state and their social environment. In this study, we investigated the role of leptin, a hormonal signal of high energy balance, in regulating the vocal advertisement display of Alston's singing mouse (Scotinomys teguina). To ask how internal cues of energy availability are integrated with external social cues, we manipulated perception of energy balance using exogenous leptin, and perceived social environment through acoustic playback. We found that both song playback and leptin injection promoted increased song effort. In the absence of song playback, leptin altered amplitude modulation in songs but did not affect song rate. Additionally, we examined hormone and playback effects on non-vocal behaviors and found that leptin may shift physical activity away from cage exploration and toward wheel running. These results demonstrate that male singing mice use both social context and energy balance to govern their investment in advertisement song, and that leptin acts as a mediator of this process.