Meeting Abstract
The elaborate displays used in courtship and aggression are among the most diverse and striking phenotypes in animal behavior. Such extravagant traits impose costs, and signalers often adjust effort to reflect body condition. Tremendous effort has gone into understanding whether females use these traits as proxies for male condition. Remarkably little work, however, has asked what condition is, and how it is used to inform signaler decisions. We use a novel mammalian model, the singing mouse, Scotinymys teguina, to investigate these questions. Singing mice live in Central American cloud forests, and make elaborate trills used in mate choice and male-male competition. In natural populations, we examined a broad range of morphological and physiological markers, including residual body mass, circulating fats and sugars, and plasma levels of hormones known as adipokines. We find that measures of condition fell into two major orthogonal axes – one corresponding to short-term nutrient fluctuation, the other to long term body condition (adipokines, residual body mass). Plasma leptin, which is released by fat cells, was associated with measures of song effort. In the lab we manipulated perceived body condition by blocking fatty acid oxidation with 2-mercaptoacetate (2MA). 2MA increased feeding and foraging behavior, but significantly reduced song effort. Among 2MA-treated males who did sing, songs changed significantly in structure, including increases in internote intervals and reductions in frequency modulation. To examine the neural mechanisms by which condition could influence social response, we injected pseudorabies virus into the larynx and traced its innervations to brain regions relevant to aggression, mating and energy balance. Current work seeks to refine these relationships through immediate early gene studies and functional genomics.
