Outdoors: 'The younger and less dominant males become "sneaky copulators"'

Along the banks of the gushing burn newly arrived fieldfares cackled and bickered as they gorged on the ripened red clusters of rowan berries. And then the air was broken by a strange echoing noise; a deep roar in the distance that carried far into the wind. The more you listened the more the sound became apparent.

Fumbling for my binoculars, a quick scan of the far side of the glen revealed one of Scotland's greatest natural spectacles - rutting red deer.

A proud stag with many prongs to his antlers bowed his head slightly and let rip with deep-throated bellow and then made a rush at another stag that was beginning to edge upon his small harem of hinds. The message was unequivocal - keep off, these females are mine!

But it was a tiresome task, and as soon as the stag engaged with one male, another would suddenly encroach onto the other side of the harem, causing the stag to rush back again in anger and snort its defiance.

It was apparent that this Monarch of the Glen would be able to cope with such pressure for only so long and he would soon have to mate with the hinds to ensure that his genes, and not those of the other circling stags, are carried through to the next generation.

For a stag the aim of the rut is simple, to try and mate with as many hinds as possible. To do so, the older more mature stag rounds up a harem of hinds, and the bigger and stronger he is, the more he can get and protect for himself.

But it is impossible to keep an eye on all of them all of the time. This has resulted in different mating strategies, with some of the younger and less dominant males becoming "sneaky copulators", waiting for the opportunity to quickly rush in and mate with a hind when the attention of the harem master is otherwise diverted.

A successful stag may be able to protect a harem of up to 20 hinds, and because so much time and energy is spent on the rut, the stags are often lean and in poor condition towards the end, losing around 14 per cent of their pre-rut body weight. The rutting season generally starts at the end of September and only lasts for a few weeks.

After the rut the stags and hinds form their own separate herds and stalkers know of certain places that are consistently stag grounds, and others hind grounds. Winter is a tough time on the hill. The deer graze heavily on short grassland, and also on heather, rushes and blaeberry. In deep snow they will strip bark and eat juniper bushes.

Red deer management is a controversial and complex issue. It is universally recognised that the Scottish red deer population is much too high, which can cause a range of harmful impacts on the environment, most notably the prevention of the natural regeneration of trees.

However, deer are a vital and iconic part of our landscape. Deer carrion is an important source of food for a variety of upland animals and may be the single most important factor in determining the number of golden eagle pairs that a given area supports.

Red deer are also important economically. In addition to the direct employment associated with red deer management, various downstream activities also contribute to rural employment.

Scotland's red deer are also facing a more insidious threat. Crossbreeding with the introduced and smaller Japanese sika deer, brought to the country in the 19th century, is threatening the genetic integrity of our native reds.

Not only is this undesirable, but it could also have a complex ecological impact that has still to be determined by scientists.

This article was first published in The Scotsman on 2 October, 2010