Does testosterone underly the interplay between male traits and territorial behavior in neotropical poison frogs?

The ability of individual animals to defend a territory as well as various phenotypic and behavioral traits may be targets of sexual selection used by males to evaluate their competitors or by females to choose males. A frequent question in animal behavior is whether male traits and characteristics of their territory are correlated and what are the mechanisms that may mediate such associations when they exist. Because hormones link phenotype to behavior, by studying the role of testosterone in territoriality one may come closer to understanding the mechanisms mediating correlations or lack thereof between characteristics of territories and of males. We evaluated whether variation in characteristics of territories (size and quality) are correlated with variation in morphology, coloration, testosterone, heterozygosity, and calls in two species of poison frogs. The Amazonian frog Allobates aff. trilineatus exhibits male care and defends territories only during the breeding season, while the endangered frog Oophaga lehmanni displays maternal care and defends territories throughout the year. We found that morphological traits (body length, weight, thigh size), call activity, and testosterone levels correlated with size and various indicators of quality of the territory. However, the direction of these correlations (whether positive or negative) and which specific morphological, acoustic traits or testosterone level variables covaried depended on the species. Our findings highlight an endocrine pathway as part of the physiological machinery that may underlie the interplay between male traits and territorial behavior. We were able to identify some male traits related to territory attributes, but whether females choose males based on these traits requires further research.