Leptin regulates song effort in Neotropical singing mice (Scotinomys teguina).

Sexual signals are often elaborate, even spectacular, behaviours. The reproductive rewards for successful display are great, but so are the potential costs. These costs include not only the resources needed to produce a display, but also resources required if the display evokes attack from a rival or predator. To maximize payoff, individuals must monitor both internal and external cues to adjust display effort. We know surprisingly little about how these competing demands are balanced. Leptin, a hormone secreted by adipose tissue, regulates energy allocation to functions as diverse as feeding, sleep, reproduction and immunity. Despite evidence that leptin influences reproductive trade-offs, its role as a putative regulator of courtship display is poorly understood. Here we examine the use of interoceptive and exteroceptive cues to modulate display effort in Alston's singing mouse, Scotinomys teguina. We manipulated individual perception of energy balance through intraperitoneal injection of exogenous leptin, and we manipulated social context through playback of conspecific song. Leptin-injected mice responded with song to playback more frequently and more quickly than saline-injected controls. Although leptin seems to promote increased song effort, we found that leptin also reduced song duration. Song effort increased after leptin injection and playback of conspecific songs. Understanding the mechanisms by which animals respond to internal and external cues broadens our understanding of context-dependent display as well as behavioural plasticity more generally. • We examine how energy balance/social context affect display effort in singing mice. • We injected mice with leptin or saline before or after exposure to conspecific song. • Song effort increased after leptin injection and playback of conspecific song. • Leptin injection changed song effort in ways consistent with residual body mass. • While leptin seems to promote increased song effort, it also reduced song duration. [ABSTRACT FROM AUTHOR]