Morphological variation and allometry of the baculum in stoats, Mustela erminea (Carnivora, Mustelidae) from Western Carpathians

Abstract

In this study we investigated allometry and variation in the baculum of the stoat Mustela erminea and compared it with head-and-body length not involved in reproduction. The stoat is a species with pre-copulatory selection (manifested by the high degree of male-biased sexual size dimorphism) therefore we predicted that baculum allometry may be isometric or exhibited negative allometry. We also test the hypothesis that the baculum size is positively correlated with adult body size and may be used as a reliable indicator of male good condition. Results presented in this study were different according to which regression model type was used. While the OLS slope for baculum length in M. erminea indicated negative allometry, the RMA model showed positive allometry. The results obtained for M. erminea weren’t in agreement with mentioned hypothesis that if baculum allometry is affected by the degree of pre-copulatory selection relative to post-copulatory selection, then we predict isometry or negative allometry of the baculum. Nevertheless, we suggest, that to confirm the above statements further analysis of more numerous material of M. erminea coupled with comparative analysis of testicular growth studies are needed to fully understand the importance and function of the baculum relative to the mating system.