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
