While size may not matter when it comes to humans, a new study published in Behavioural Ecology and Sociobiology found that the width of the male bank vole’s penis plays a role in social dominance.
Male bank voles have a bone in their penis known as baculum. While these bones are not present in humans, they can be found in a variety of different mammal species. The function of this bone has not yet been determined, but this new study does show that when it comes to the bank vole, it plays an important role.
The new study, led by Dr. Jean-Francois Lemaitre from the University of Liverpool, looked at the male bank vole to determine what contributed to social dominance. They collected wild bank voles and studied their offspring.
They paired the young males up and exposed them to female nesting material. Scent mark patterns were then recorded and the males that left more scent marks were determined to be the dominant of the pair.
The next step was to then scan the baculum of all the males and evaluate the images. While many previous studies have focused on the penis length, the researchers discovered the real difference was in the width and that the dominant males have a much wider baculum than their subordinate male counterparts.
Lemaitre believes the possible explanation may be that female bank voles need physical stimulation in order to release eggs and that this wider baculum may provide this stimulation and result in a greater reproduction success rate.
He believes that this study may be the first step toward understanding the connection between genital structure and reproductive success.