"Here's the new King", the woodland animals are told. And there in front of them tumbles a just-born fawn with wide curious eyes and legs like filigree: the most vulnerable being in the world Deer tap deep into an age-old paradox. It is common to all Europe, like the deer, but it tells most sharply in British imagination, because of our seven-hundred-year tussle with the monarchy. It concerns kingly power - and all male power, which can be symbolized by Kings.

However lofty and magnificent Kings (or males) are, they are also seriously fragile. A mature stag carries a whole candelabra of aggressive masculine display on his brow, his crown and his weapon in sexual battle. (Homo sapiens apart, deer are one of the few animals in which sex is triggered by the male. It is the stags that get "horny": hence Stag Lager, stag nights.) But a stag is also the perennial victim, the most hunted, vulnerable animal.

Bambi was written by the Austrian novelist Felix Salzmann. Born 1869, Salzmann was strangely interested in imagining the secret life of hunted wild vulnerable things, for another of his novels conjured up the experiences of a Viennese prostitute. Bambi - mysterious, beautifully written, desperately sad - is all about accepting loneliness and loss. It first hit English eyes on a rough Channel crossing in March 1928, when John Galsworthy forget to be sea-sick as he threw himself on the proofs of the English translation by Wittaker Chambers. When Disney took over, he lapped the story in a treasure-house of Victorian visual cliché: Landseer's Monarch of the Glen, the stag at eve, stag at bay. You first see Bambi's father, "The King of the Forest", as a shadow crowned with branchy antlers which become, retrospectively, a crown of thorns. He is what Bambi will be, a gentle king, always under threat: the high altar of doomed animality and masculine power.

British deer terminology is hooked into the history of the aristocracy and monarchy. But it still goes on. A hart is still the name for a stag over five years old; a hind is a doe three years or more. The hart, especially the white hart (think of all those pubs), has long been a British royal emblem. Later on, deer became a mark of upper-class rank and wealth: you stocked your park with them. Elizabethan maps show more than eight hundred private deer parks all over Britain. Deer-stalking on foot became fashionable among the Victorian gentry. Deer went deep in folk imagination too. You can see it in carols and hymns. "The rising of the sun and the running of the deer". "As pants the hart for cooling streams, when heated in the chase".

Deer in a wintry landscape have a peculiarly hushed, British, this-is-the-land-we-belong-to Christmas card impact. See Thomas Hardy's poem, "The Fallow Deer at the Lonely House": One without looks in tonight... We do not discern those eyes Watching in the snow. But though deer have always been the imaginative property of commoners, they originally belonged, very strictly, to the king. When the Normans conquered us, they imposed a new Forest Law to enclose "the King's Forest". Its main purpose was to keep "the King's deer" for the King alone to hunt. A dead deer was a worse crime than a dead man. If a serf was caught killing one he was sentenced to death. Yet all that meat on the hoof was impossible to ignore, so deer-poaching instantly became one of the strongest British traditions. Every Robin Hood film starts with a peasant killing a deer, pursued by King's men, protected by Kevin Costner or Patrick Bergin.

Then there are the more symbolic aspects of deer. Christianity is full of paradoxes about victimhood and power, so deer became a strong religious emblem: St Hubert was converted while hunting on Good Friday, by coming up against a vision of a crucifix in the antlers of his stag. But all that fleet, hunted, shy grace played right into the sex war too. Tudor poets used deer-hunting as an easy code for sexual pursuit, full of puns on deer and dear, heart and hart. Sir Thomas Wyatt wrote a poem about someone else's girlfriend, probably the King's: Whoso list to hunt, I knowe where there is an hynde, But as for me, helas, I may no more. That girl was the king's dear. She seemed tame but was "wylde for to hunt". When he splits up with another, he mourns her "stalking within my chamber", taking bread at his hand, kissing him and saying "Dear Hart, how like you this?". In The Merry Wives of Windsor, Falstaff is beaten up and half-drowned in pursuot of two married women, who get him to dress up in deer horns and meet them at night in Windsor Forest: There is an old tale goes that Herne the Henter, Sometime a keeper here in Windsor Forest, Doth all the winter-time, at still midnight, Walk round about an oak, with great ragg'd horns. Waiting with "huge horns on his head", Falstaff prays "the hot-blooded gods" to help him take on two women at once. "Send me a cool rut-time!" When the women appear he gets to work ("Who comes here? My doe with a black scut?") but then the townsmen turn up disguised as fairies to torture and "dis-horn" him: while, in the sub-plot, a young girl slips away to marry the man she loves. That sinsiter sexy figure, the horned man, "Herne the Hunter", presides over rude sexual disguise and shennanigans, in the woods.

But a man in horns is an uneasy emblem and brings out the vulnerability in deer symbolics: for stags shed those antlers every year. That gorgeous male symbol will - nightmare of nightmares - drop off. (Different species shed antlers at different times of year; Red Deer, for instance, shed in February.) You find the antlers lying about the forest. They do grow back, but very itchy: stags rub them furiously on trees. In all of nature, there is no more glorious, or more ambiguous sex symbol. Every rampant stag, sexual victor of his "dear", is fated to lose his horns. And they may become those of - a cuckold.

Stag night dreams and nightmares apart, what do real deer get up to in Britain today? We now have seven species. Once upon a time there were Elk and Reindeer too but the last Ice Age wiped them out. The largest left is the Red, our biggest native land animal. It lives about twelve years, and only in wild terrain: Scotland, the Lake District, Exmoor, the New Forest, wild bits of Ireland. Stags grow four foot at the shoulder, with branchy antlers three foot or more. Most of the year they live in single-sex herds, drifting from dusk to dawn, spending the day resting or, in summer, wallowing in mud, which protects them against summer flies. They also defecate and pee in the mud (so much for the fragrant sparkle of a Babycham), which increases their smell, and therefore pulling-power, in the autumn rut.

If you are a deer, your mating pattern depends on how much of a herding species you are. Most deer herd, and the stags proceed by developing a "rutting stand", which in Red Deer lasts six to eight weeks. The stags bellow like maniacs, their necks swell, they roam in the open calling up does with a roar. Does come to them; and stag fights for them may last hours. The rut is triggered in the stags by several factors, including the number of hours of daylight and the effect of daylight on the pineal gland. When they have gathered as many does as they can, they wait impatiently till the does come into season. All of it is light years away from the delicate teenage pairing-off in Disney's Bambi.

Our only other native survivor of the Ice Age is the little Roe: two foot high, timid, hard to see. If you upset them they bark loudly and bound away. In Hampshire, North of England and Scotland, but not Wales or much of central England, Roe hide during the day in thick cover: scrubland, woods with dense undergrowth. And Roe do not go about in herds. You see them in twos or threes, depending on their sex and the time of year. Since they do not herd, they have a different rutting system: stags go and hunt for doe and shed their small, spiky antlers in November. From Elizabethan times these shy little Roe were virtually wiped out from Southern England. After the Reformation, they were re-introduced from the Continent, so now we have different variants - experts tell them apart by subtle differences in conformation - and the original, pre-Ice Age lot live only in Scotland. Roe elsewhere - Hampshire, Exmoor, Lincolnshire, wherever - come from the Continent, but these too have regional variations. The experts can tell, by the bone structure, exactly where in Europe they came from.

The Fallow, about a foot lower than the Red and more restless, with a delicately dappled caramel coat, is our oldest, most important deer guest. The Ice Age eradicated them; they were brought back by human beings, possibly the Phoenicians or Romans. But it was those Normans, addicted to hunting Fallow in the great French forests, who decided the Fallow's British cv and poured them into British forests. They have been with us for a millennium, and played a vital role in the English landscape. From Norman times, parks as well as forests were stocked mainly with Fallow. It is hard not to feel that the central attraction of Fallow Dee, for testosterone-driven, alpha-male Elizabethan dandies ordering deer herds for their newly-planned parks, was the size of their antlers. Fallow deer have more mass of antler than any other deer., They are the ones whose antlers, spreading out at the top like trees or proudly waving royal hands, are known as "palmated" in the trade. From the stag's point of view, the antlers have three uses, and their velvet-cod-piece-flashing owners would identify with at least two of those. They are a battle weapon, for getting sex; they spread the attractively musky scent created in the stag's facial glands; and above all, they flag a stag's social status. When the horns drop they immediately start re-growing bigger, like the new year's new Mercedes.

How simple we all are, deer and men. The bigger the antler, the higher the status. Size does matter: more than anything Stags invest an extraordinary amount of cellular energy to score this social point. The antlers are living bone tissue, covered in velvety skin full of blood vessels, to feed the bone as it grows. When the horns reach their allotted size for the year, they stop; become dead bone; the velvet begins shucking off in bloody ribbons. If you check out Fallow Deer in your local park - I went down to Golders Hill Park North London - you can see these annually re-architectured artefacts on the stag himself. There he is, chewing the cud, surrounded by his herd, so sure of himself that when a magpie rudely runs along his back, he ignores it. The does chew their own cud peacefully beside him; this year's fawns (all his) graze nervously round them, twitching spoony ears, flicking up gorgeously twiggy legs to canter off iwhen startled by a barking dog. Your neck muscles ache just watching him hold that crowny packet of six-bore spikes and massed bone off the grass. If you get closer, with a trainspotter's guide to antlers in your hand, you can identify each spike.

Since it was the Normans brought the Fallow from France, the parts of an antler names are franglais, and the masculine yen for anorak labelling is even more obvious than French influence. The spreading bit, where the bone joins the head, is the "coronet". (Royalty gets everywhere, where deer in Britain are concerned.) Go up the horn, in front, and you reach three spikes: the "brow tine", "bez tine", and "trez tine". Then comes the palmy bit at the top. Down the back are jagged waves known as "spillers", which lead down to the backwards spike, the "guard tine", and back to the coronet. It was this spectacular display of aggressive social superiority, this breath-taking alpha male-itude with the bonus of beautifully nameable different parts, that made Fallow so popular on the deer park circuit. Golders Hill Park will tell you, too, all the anorak names for stages of an antler. At four months, a buck fawn has little swellings called pedicles; at a year, little pointed spikes called, er, prickets. At two (the "sorrel" stage), palmation begins; so do the brow and trez tines. At four and five (the "sore" stage), the spillers spread back over his shoulders. The equipment he'll carry the rest of his life - Fallow live till about twelve - is now taking its final shape and he is now a full fledged hart. Britain has three other wild deer now, the Sika, Muntjac, and Chinese Water Deer, all imported into Britain long after the Fallow in the nineteenth-century craze for exotic breeds. Fancy deer appeared on private estates and then started escaping, helped joyfully by poachers.

The Sika, from Asia, has a winter pellage (more franglais, meaning coat-colour) of blackish grey or brown, blooming a white-spotted red-blonde in summer, like Fallow. Sika come into rut roughly the same time as Red and Fallow, but shed their antlers in April. You see them in parks, or wild in woodland and farmland; there is a small herd on Lundy Island. The Muntjac, our smallest, came from India and China, escaped from Woburn Abbey around 1900, and is now common everywhere, from Cornwall to the Scottish Borders. They are roughly the size of an Alsatian with a foxy red coat, and as they slip along the edge of a cornfield, they do look a bit like large foxes. Up close, though, you see the little horns and tusky canine teeth. They are secretive: for every one or two you see, there are probably twenty more you don't. They have had a bad effect on Roe, for they eat the same food but reproduce more quickly, since they don't have a special mating season and the does spend their whole life getting pregnant.

And it is food that is the great problem about deer. The Yearling, that intense Bildunsroman by the great Florida environmentalist Marjorie Rawlings, is also, like Bambi, about coming to terms with loneliness and loss. The boy's father has to shoot his pet fawn when it eats their precious corn. In Britain, woodland was continually giving way to farmland (the Norman forest law tried to preserve something that was bound to pass away with population expansion) and in farmland deer are not a privilege, but a pest. To ask about this, I phoned the British Deer Society, a charity outfit with five and a half thousand members (many deer-ophile urbanites among them), set up forty years ago. What about deer environment and deer control? What are the problems? What do deer-lovers say? "We love deer," the Secretary told me. "They are wonderful animals. For us, their welfare is paramount. But their numbers have to be controlled, simply to protect their own habitat from them." Forget literarure and symbolism: this is the big paradox where real-life deer are concerned: that they are the great destroyers of the environment they love. Our three large species, Red, Fallow, and Sika, are mainly grazers but nibble shrubs as well; the little ones, Roe and Muntjac, are mainly browsers on shrub, but graze too. And all will gobble up the young trees' soft new growth, if they can.

All deer love forests. Even Scotland used to be forest. If you asked deer on the moor today, they'd say they'd like the forests back, please. But give them trees, and they devour them. To make a deer forest, you have to protect it: make a corridor for deer to move through, provide shelter in established trees, large enough not to be eaten, where they can lie up in during the day and screen their fawns; and above all protect young trees with fences or tree guards. Deer can clear six foot fences so most foresters use guards; but even these have got to be high enough. "I've seen forests decimated because the guards were only four foot six: ideal snacking height for Fallow," said Mark Squire of the Deer Society. "Deer can inflict catastrophic damage on a fragile environment. Ten years ago Muntjac completely wrecked a Site of Special Scientific Interest at Monk's Wood near Cambridge."

So we end where we began, with the deer's terrible vulnerability to ourselves. Wherever deer are, culling has to go on all the time. And hunting was what the Fallow were brought here for, by Normans; what the New Forest was made for. There are few packs of staghounds left. (Not deerhounds, in fact, but floppy-eared skewbald hounds bred up from foxhounds.) The packs are mainly in the West Country- the Devon and Somerset, Tiverton, and Quantock Hunts - and only hunt Red. There are informal packs of "buck-hounds" (not recognized by any Hunt headquarters): a collection of hounds and dogs whom people follow on foot, mainly after Roe. And deer-stalking for Sika, Roe and Red is big business, especially in Scotland. So there you are: the paradoxes, history, sex symbolism and current problems behind that road sign of a running stag on the motorways of Hampshire and Exmoor. You see the sign, not them. But you know they're there: the royal, beautiful, timid, sexy secret, both vulnerable and destructive, of the last forests left in Britain.