Female dolphins’ vaginas have evolved to reject males
11 Oct 2017
Female bottleneck dolphins have evolved to be able to prevent certain males from reproducing with them.
A study of some species of marine animals’ genitalia found that bottleneck dolphins have extensive vaginal folds that make penis entry more difficult.
Researchers said male dolphins work in groups of two to four to seek out females, and females have little choice of who they mate with.
But Janet Mann, of Georgetown University, told New Scientist: ‘She may not choose who she mates with, but might be able to choose which male or, more precisely, which sperm, fertilises her egg.’
Subtle movements during sex can prevent the male from fertilising the female, the scientists said – giving them the ability to control paternity.
Though marine biologists have been able to study male genitalia, less is known about the female genitals of dolphins and other cetaceans.
Researcher Dara Orbach of Dalhousie University in Canada created moulds of cetaceans’ vaginas.
Along with Patricia Brennan from Mount Holyoke College in Massachusetts, Orbach obtained the penises of marine mammals and inflated them to see how they would look when erect.
Comparing them with the vagina moulds showed that both the bottlenose dolphin and the porpoise have the vaginal folds.
The findings are similar to those previously found in duck vaginas, which have evolved to make it tougher for males to force reproduction.