Sheep with Smaller Horns Live Longer

The alpha male doesn't always get ahead in life.  A new study on wild sheep has shown that although males with bigger horns win more females, males with medium or short horns live longer.

The study, conducted by researchers at Universities of Edinburgh and Sheffield, also explains why short and medium horns survive longer, even though they might hinder breeding success of a sheep.

Researchers studied sheep horns, which help them find mates- much like elephants' tusks or deer antlers. Sheep horn size is controlled by a set of genes.

They found that although males with bigger horns won more females, but rams with shorter horns lived longer.

They also found that sheep with medium-sized horns carry and pass the short-horn gene to the next generation just as successfully as their big-horn counterparts. The study was based on 20 years' worth of data obtained from wild sheep from St Kilda, Scotland. The sheep in the study were Soay sheep and they are smaller than the domestic sheep, BBC reported.

"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," said Dr Susan Johnston of the University of Edinburgh's School of Biological Sciences, one of the study authors, according to a news release.

The study is published in the journal Nature.

Related study on Soay sheep has shown that more promiscuous, big-horned rams mate with several female sheep during the annual rut- sometimes up to 13 times a day, but the exhaustion leads to poor-quality sperm. On the other hand, weaker males don't get to mate too often, but when they do, they deliver high-quality sperm.