Culling female deer in the Scottish Highlands is the best way of preserving the environment and maintaining a healthy population of stags for commercial shooting, scientists said yesterday.
Female red deer outnumber stags and the heavy bias towards females is one of the principal reasons the land is heavily overgrazed, according to a study by a team of university zoologists.
They found that if estate managers concentrated on culling hinds the population of stags would rise, allowing more income to be generated from tourists who paid a premium to shoot adult males, as well as curbing the worst overgrazing.
A failure to cull enough females has led to fewer males and damage to the environment, according to the study by a team from the universities of Cambridge, Edinburgh, Imperial College London and Scottish Natural Heritage.
"Because males are typically culled by fee-paying hunters and generate more income than females, income will decrease as the male harvest falls," the scientists report in the journal Nature.
Tim Coulson, a zoologist from Cambridge University and a member of the team, said that managing red deer was an important economic and environmental 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," Dr Coulson said.
"To maximise the quality of their males, herd managers must protect them from competition with females by humanely culling them."
There are about twice as many females as males in the red deer population of Scotland and there seems to be a threshold proportion of hinds that causes a demise of stags, either by migration away from the herd or by early death. The scientists have followed a population of more than 2,000 deer over 30 years on the island of Rum. They found that as the proportion of hinds rose to a maximum that the environment could sustain, the males did progressively worse, either by dying young or dispersing to other herds.
Tim Clutton-Brock, professor of zoology at Cambridge, said estates managers, who charged up to £200 for the right to shoot a stag but next to nothing to shoot a hind, had been reluctant to cull females because of fears that this would also affect the male population.
"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 vegetation," he said. "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."
The red deer population of Britain is responsible for a considerable amount of environmental damage through overgrazing. With no natural predators, their numbers have increased substantially over the centuries.