Sources of acoustic variation in the advertisement vocalizations of Neotropical singing mice

Patterns of variation in communication systems provide important insight into the processes that shape phenotypic evolution. Although studies in anurans, birds, and insects indicate that diverse selective and stochastic forces influence acoustic signals, factors that shape variation in mammalian vocalizations are poorly understood. Neotropical singing mice (Scotinomys) are diurnal, insectivorous rodents distributed throughout montane cloud forests of Middle America. Males commonly emit species-specific advertisement vocalizations that are used in mate attraction and male-male aggression. To explore factors contributing to vocal variation, we summarize data from a diversity of studies at disparate scales and levels of analysis. We highlight the importance of genetic drift in shaping population differentiation, the role of androgens in modulating the performance of physically challenging displays, the influence of social context in shaping posture and vocal parameters, and the impact of the ambient environment in affecting sound propagation. Neotropical singing mice are emerging as an important model that enables us to draw parallels to vocal communication systems in traditionally more tractable species.