Formosan Sika stags are males, hinds are females and their young are calves. If they're fallow, then it's bucks, does and fawns.". Jim Brannan, Cornbury Park's deer manager, clearly knows his stuff.

For a millennium, deer have been part of Cornbury, which is first mentioned in the Domesday Book. The park became included in Wychwood Forest as a royal property and the Keeper, normally a royal favourite, was responsible for providing royal hunting facilities and supplying venison to the royal kitchen.

Jim said that, in 1089, permission was obtained for a buck leap-in, an earth ramp on the forest side of the fence that encouraged wild deer into the park but prevented escape.

As he tells the tale, we are sitting in his Land Rover watching what he calls The Boys' Club, Sika stags and fallow bucks lying companiably together and chewing the cud. Hinds and does are elsewhere, the sexes only get together at rutting time.

Cornbury has a herd of around 450 deer, a mix of Formosan Sika and the native fallow, although Sika hinds outnumber fallow does. The foreigners' were a present from Woburn many years ago.

Colours vary according to species and time of year. Fallow have four main colours - Common, Menil, White, and Black or Melanistic. The summer coat of the Common is deep chestnut with white spots, which turns to dark grey-brown in winter and the spots fade. For a Menil, the coat is similar but with more spots. Come winter, the brown darkens but the spots are still visible.

White fallow are born cream, becoming paler as they mature. Black have no spots at all and their coats shade to greyish brown. Sika are dark chestnut in summer, moving to liver brown in winter.

Genetically, the two species are poles apart and there is no interbreeding, no competition and no fighting. The Boys' Club only came into being some years ago, when a section of the park wall collapsed and a number of prime bucks escaped. The young fallow bucks or prickets suddenly found they had nobody to sit with and palled-up with the Sikas.

The pricket or single spike is the first antler of a young buck or stag, beginning as a pedicle during the winter and developing to full size by late summer. This first head is retained until the following summer, when it is cast, with new antlers starting almost at once.

Antler growth for all ages is controlled by testosterone. At the initial stages, testosterone is low and the antlers are covered in velvet of the same hue as the coat. As hormonal levels increase, the blood supply to the antlers is cut off, the velvet dies and is rubbed off on surrounding branches and hedges; the deer are said to be in tatters. Then the antlers harden, multiple spikes for the Sika and the more spatulate for the fallow.

As the rutting season approaches, testosterone levels soar, reaching a peak in late September and October for fallow and October and November for Sika.The rut is a whole new world, where rampant sexual desire and a harem are everything and old friends become - temporarily - deadly enemies.

Each male defines a rutting stand, often the same one each year. He digs out a wallow some two or three feet across, urinates in it and then rolls in the liquid. This hormone-laden fluid becomes an aphrodisiac, what Jim laughingly terms "the Chanel of the deer world", used to attract up to 20 females which are kept near the wallow.

Any male of the same species foolish enough to approach the stand is asking for trouble and horns become locked in adrenaline-fuelled combat. This is a power struggle, with the aim of forcing your opponent backwards rather than a fight to the death, but the pointed antlers of the Sika often cause wounds, sometimes the loss of an eye.

Within days of the rut ending, rivalries are forgotten for another year and The Boys' Club is back in session.

"Curiously," said Jim, "a fallow buck can wander through a Sika's rut or vice versa and it's as though the trespasser is invisible. Just let one of his own kind try that!"

Calves and fawns emerge the following May or June in The Thorns, Cornbury's deer nursery. This is an area of thorns, brambles and bracken left totally untended. Thorn trees will grow to a certain height, then blow over in the wind, but just like a lay-down hedge, they will keep growing any branches exposed to the light.

The whole of The Thorns provides windbreaks and hides ideal for calving and is used by Sikas and fallows alike. Unlike domestic farm animals such as sheep, deer give birth quite naturally and require no outside intervention. From the age of two, fallow does will fawn every year, probably for 12 to14 years, but the Sika hinds will have years off, with up to 25 per cent of hinds conceiving very other year.

Food at Cornbury is in abundance. Laid out in the 17th century, the deer avenues have an oversupply of grass and were sown with the right kind of trees.

During the rut, a male will eat and drink very little, powered by adrenaline to fight and mate. After five or six weeks, he will have lost a third of his bodyweight, winter is nigh and a vitamin boost is critical. The avenues are populated by oaks and horse chestnut, acorns and conkers bursting with nutrients to restore lost vim and vigour.

For the females, the key period is spring, when they seek a tonic to guarantee milk for their young. Enter the lime tree, planted on the west of the avenues to catch the prevailing south-westerly and blow the sweet scent of the fragrant, protein-laden buds and flowers towards the hinds and does.

The prevailing wind in the Evenlode valley is still south-westerly, so that part of the climate is unchanged over the centuries.

Looking at all these trees, it appears that the underside of each has been cut with a precision tool. All becomes clear when the precision tool' rears up on its back legs to snatch a juicy titbit from the lower branches, and creates what is known as the browse line.

In hard winters, food is supplemented by hay, which fits into the normal diet with no adaptation.

Yes, life for deer at Cornbury Park is very sweet.