' Since males have finite resources to allocate to breeding, they allocate them carefully to each mating to maximize their number of offspring,' Tazzyzman added.

'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. Thus, there is a trade-off between number of matings and success per mating.'

'A possible case can be seen in chickens, which in the wild live in groups of varying numbers of males and females. Females mate with many males, so males are subject to sperm competition,' Tazzyman said.

However, the attractiveness of a male is determined in large part by his social standing. Males higher up the pecking order find it easier to secure matings with the females, but they transfer fewer sperm to females.

The study is slated for publication in the American Naturalist.