Couples undergoing infertility treatment may be interested to learn that the attractiveness of the man could have an impact on their chances of success.
Scientists at University College London (UCL) and the University of Oxford have discovered that males more in demand among women, in other words who may be more attractive or have a higher status, are likely to produce less fertile sperm.
The findings will be published in the journal American Naturalist and reference previous studies, which revealed that in different species the fertilising quality of each mating is relative to the privilege of access each male has to females.
Sam Tazzyman, from the centre for mathematics and physics in the life sciences and experimental biology department at UCL, explained: "If a male puts a lot of resources into each mating he will get more offspring per mating, but at the expense of fewer matings.
"If, on the other hand, a male puts few resources into each mating he will secure less paternity per mating, but will be able to carry out more matings overall."
Sperm are transported within semen, which is a fluid and can live within the female reproductive system for as long as three days.