Males suffer from having too many females

The team, from Cambridge, Edinburgh, Imperial College and Scottish Natural Heritage, have spent the last 30 years following the fortunes of more than 2,000 red deer on Rhum - studying their movements, breeding successes and survival.

Their results have shown that, as the number of hinds in the herd rises towards the maximum that the environment could sustain, the males are progressively more likely to die young or disperse into other herds as adolescents.

In addition, the researchers found that fewer males were likely to migrate into the herd from elsewhere. Since deer forests derive most of their income from culling males, this fall in numbers has a big impact on their revenue.

Tim Coulson, in the University of Cambridge Department of Zoology, explained:
"Deer management is an important issue in many parts of the Highlands. Our results show that if an estate has large numbers of female deer, many of the best stags will migrate to neighbouring estates, while the young ones die out. To maximise the quality of their males, herd managers must protect them from competition with females by humanely culling them."

Where herd managers fail to cull enough females, the younger males are likely to disperse, benefiting neighbouring herds that are keeping female numbers low. Previous research by Cambridge zoologists has shown that males tend to lose out in competition for resources with females in many animals where males are substantially larger than females. This effect is probably not confined to red deer.

Professor Tim Clutton-Brock, also of the University of Cambridge Department of Zoology, added:
"Conservation agencies in Scotland have been trying to persuade deer managers to reduce female stocks for over 20 years in order to limit their impact on the vegetation. Some landowners don't want to harvest more females because they believe it would reduce the number of stags they could cull. We have shown that this belief is misguided."