Large horns attract females, but rams live shorter lives
Physical dominance can give some wild animals the edge over their sexual rivals – but their weaker competitors have some breeding advantages too, a new study suggests.
Researchers from the universities of Sheffield and Edinburgh studied wild sheep living on the island group of St Kilda, Scotland, and investigated the size of males’ horns – a characteristic that can help them to attract mates, much like deer antlers or peacock tail feathers. Scientists discovered a gene that controls horn size and found that rams can grow large, medium or small horns, depending on the genes they inherit from their parents.
The research, part-funded by the European Research Council, shows that although large-horned rams win more females in the annual rut, rams with small or medium-sized horns are more likely to live longer. In addition, sheep with medium-sized horns carry the ‘small horn gene’ and can pass it on to successive generations by mating as successfully as their big-horned cousins whilst living relatively long lives.
Commenting on the research, Dr Susan Johnston of the University of Edinburgh said: “Until now, we did not fully understand why small horns had not died out. Although it may appear that larger horns are better, we found that the increased survival of medium-horned rams allowed them to catch up with their big-horned rivals in terms of how many offspring they have. As they are carriers of the small horn gene and have many offspring, this means that small horned rams will continue to turn up in the population.”
The study is published in the journal Nature.
