London, July 10 - Attractive males release fewer sperm per mating to maximise their chances of producing offspring across a range of females, according to a new study.

The findings by researchers at UCL (University College London) and the University of Oxford suggest that, paradoxically, mating with attractive males may be less fertile than those with unattractive ones.

The team mathematically modelled a range of male ejaculation strategies to look for the optimum 'sperm load' per mating, and how this might vary depending on mating patterns.

Previous studies have shown that domestic fowl, and fish such as the Arctic charr, males with privileged access to females produce ejaculates of lower fertilising quality than subordinate males.

Sam Tazzyman, UCL CoMPLEX (Centre for Mathematics and Physics in the Life Sciences and Experimental Biology), said: 'In some species, females mate with many different males.'

'Each male's sperm competes with that of other males in a process known as 'sperm competition.