Genitals tend to be tucked safely out of the way when not in use, but in some cases, yes – they can be a liability, says Stuart Blackman
One of the few groups in which this has been studied is guppies and their relatives, which are rare examples of fish with internal fertilisation.
- "A male's penis may be all that a female has to go on when assessing the quality of her suitor."
- Which animal has the biggest testicles? The results might surprise you...
Males deliver their sperm with a penis-like anal fin, which cannot be retracted. Well-endowed males are more likely to copulate, but at a cost to their swimming speed, which is important for evading predators.
This may be the result of increased drag and/or that a big ‘penis’ comes at the expense of muscle mass.
