Field mice
Mother mice that have to compete for mates have sexier sons (wiki commons)

Male mice born to promiscuous mothers live fast and die young, attracting more females than the average mouse, researchers have found.

Biologists at the University of Utah have found that when mother mice compete socially for mates, their sons produce more urinary pheromones that make them smell sexier to females.

Female mice mate more often with males that produce scent marks saturated with pheromones. Previous research has shown mice from promiscuous parents produce a third more offspring than their monogamous counterparts.

However, there is a downside to smelling sexy, as it considerably shortens their life expectancy - only 48% of the sexy mice lived to the end of the experiment, compared 80% of the males whose mothers were not promiscuous.

Wayne Potts, senior author of the study, said: "If your sons are particularly sexy, and mate more than they would otherwise, it's helping get your genes more efficiently into the next generation.

"Only recently have we started to understand that environmental conditions experienced by parents can influence the characteristics of their offspring. This study is one of the first to show this kind of 'epigenetic' process working in a way that increases the mating success of sons."

Pheromones expensive

Published in the journal Proceedings of the National Academy of Sciences, the researchers said the sexy mice lived shorter lives because of the energy spent producing the pheromones.

"Production of pheromones is outrageously expensive," Potts said. "A single mouse's investment in pheromone production compares with the investment that 10 male peacocks make in the production of their tails, which also are used to attract females."

The researchers assessed the impact of the environment in which the male mice were conceived by looking at mice that lived either in a promiscuous environment where mothers had to compete for a mate and a domestic environment where they did not.

The mice were then removed and mixed up to see how the mice would breed. "Sons are primed to respond to conditions that their moms experienced - such as exposure to multiple potential mates," Potts said.

In comparison, fathers from promiscuous environment made their sons less sexy. The biologists believe this is because they would become competition: "If you're worried about your sons impinging on your own reproductive success, then why make them sexy?" he said.