When we arrive at the cottage, they are already there, watching us from high on the crags overlooking the water. The five of us are still tasting the chill, stale air of the empty building and staking claims on stained mattresses when Julien spots a silhouette through the warped pane of the back window. “They’re up there now,” he says. “Let’s go.”

A minute later we are scrambling up the hillface, gaining height fast. The wind is moving in great currents over the ridge. It comes in waves, smashing against us and then withdrawing, dragging the air from our lungs. Julien and Storm are out in front, goat-footed over the tussocks. I try to copy the way they creep through the heather on their elbows, pressing their abdomens into the mud, all the time scanning the hillside for movement.

After a while they slow to a stop and we bunch together. Storm catches my eye and points hammily beyond the boulder he is using as a windbreak. I nod, coming to rest at his feet, sinking my hands into long dead grass as if it were hair. I wait a beat, then lift my head, bringing my eyes above the stone parapet.

We are close enough to see the deer’s face in detail: her domed, almost Roman, profile. Dark eyes flashing in every direction: suspicious. I drop my head slowly back down behind the rock. Up ahead, Julien cranes forward again from his foxhole then stands up, shaking his head. Gone.

We start picking our way east, towards the narrow gorge, to trace its path back to the house. But then, there they are. Two females and a juvenile on the opposite bank. Like phantoms. They haven’t seen us. Julien twists around and gestures to Adrian: come. They go, crawling across wet earth, and disappear beneath a precipice.

A minute passes, then another. I lie back against the heather, thinking no particular thoughts. A shot rings out, impossibly loud. A moment of confusion. Then Adrian and Julien appear on the ledge below, waving us down. They got her: a crack shot, right through the spine. Dropped straight from the rock face into the water. She’s dead.

It is 13 February, and Julien and Storm have been doing this all winter long. This hind (an older specimen, unusually large, very lean) is their 21st kill of the season. But it’s not enough. Julien has a target he must hit: 30 animals – or “beasts”, as he calls them, a strange word from his French mouth – and very little time left in which to meet it. In Scotland, the hind-shooting season closes at dusk on the 15th.

Until then, here we are – four men and one woman, me – spending our days stalking deer and our nights in an empty house, with a fireplace at each end and little else. No electricity, no running water. We eat stew from a scorched iron pot over the fire, drink water from the peaty burn that runs by the gable end. Hanging from two nails by the door is a shovel that comprises the toilet.

Facebook Twitter Pinterest Deer grazing in Glen Etive, Scotland. Photograph: Jeff J Mitchell/Getty Images

A doorless lean-to slouches heavily against the back wall. It is here we take the dead deer for hanging. Julien throws a length of rope over a rafter and lowers it down, scattering bird droppings and cobwebs upon us as he does. Threading the cord through two slits cut in her hocks, he clips rope to rope and hoists her like a flag.

What was animal is now object. I observe my reactions as if from above, lifting and weighing each thought as it comes to me, alert for squeamishness. There is some. But not as much, perhaps, as I expected.

Julien bends over her rent chest, headlamp illuminating the torso from within, and sets to work again with his knife and a surgeon’s manner. It is easy to trace the path of the bullet: its entry and exit, the single shattered vertebra between. A tragedy in one act. When he’s done, we slide her down the length of the rafter, drawing her like a curtain, to make room for the rest.

No one owns Britain’s red deer. But if you own the land they live on – or graze from, shelter in, pass through – then you assume responsibility for their management. In Scotland, where their numbers have doubled in the past 50 years, such stewardship has come to mean one thing: the annual cull.

And it is in the Highlands where the country’s deer problem can be seen clearly: they gorge themselves upon gardens and crops and vegetable patches, they run blindly into the road as speeding cars approach. The true scale of the problem is hard to gauge, but our best guess is that there might now be as many as 1.5m deer in the UK, at least half of them in Scotland; more than at any time since the last ice age. They roam bare hills in vast herds – in the Cairngorms they have been seen in herds a thousand animals strong, steam rising from their massed ranks. They swarm over the fells like a plague, covering the land like a cloak, picking it clean, moving off as fast as they arrived.

And with the deer comes plague of another sort: cases of Lyme disease, spread by ticks that use the deer as hosts, have rocketed – in some areas reaching epidemic proportions. But perhaps the most pressing concerns are environmental ones. The red deer eat and eat, overwhelming a delicate moorland ecosystem, trampling the ground, shearing the hillside of vegetation and stripping the bark from the trees.

In Glen Affric, not far from Inverness, volunteers from the charity Trees for Life spent many weeks planting native trees in the stark western reaches of the glen. The charity aims to build a forest corridor from east to west coasts, joining up the remaining fragments of the ancient Caledonian Forest. But when the organisation’s founder, Alan Featherstone, returned to the site in 2015, he found their sturdy deer fences flattened by winter snowdrifts, and the saplings inside (birches, willows, rowans) bitten hard back. More than a decade’s growth had been undone in a matter of weeks. Now, until the fences are rebuilt, the shorn stems will struggle to grow: new shoots and leaves nipped off as fast as they appear, their progress arrested indefinitely.

The ascendance of the deer is attributed in part to the disappearance of one of their main predators from Britain: wolves. According to folklore, the last wild wolf in Scotland was killed in 1680, and since then cervids have roamed the country unthreatened by predators. If undisturbed, a herd of 300 has the potential to grow to 3,000 in the space of 13 years. So the role of the predator – the role of the wolf – is what the estate owners of Scotland now cast themselves in.

Facebook Twitter Pinterest Glen Affric, Scotland. Photograph: Alamy Stock Photo

Around 100,000 deer are killed in Scotland every year, the vast majority of them red deer. Some are killed on traditional sporting estates, where for generations southerners and City types have come, keen to shoot a monarch of the glen. But fewer dream of shooting the hinds – the most effective way of arresting population growth – and so the responsibility falls to the owners.

The conservation lobby are the most vociferous proponents of the culls. Those concerned with woodland and wild flowers argue for an all-out war, pointing to research from the University of East Anglia that mooted a mass cull of 50–60% of all deer in the UK. Wildlife foundations find themselves calling for the deaths of tens of thousands of wild animals.

The prospect of mass deer shooting is one that arouses great passion, although the arguments for and against come from unexpected quarters. If the environmentalists are mounting a war, then the shooting estates – those professional deer-killers – are calling for peace, for the gentle approach. They fear the culls will go too far; that something special will be lost.

Twice yearly, landowners in each region and representatives of the government body Scottish Natural Heritage convene in “deer management groups” to share their targets for the year. The collective approach is necessary, as the deer drift back and forth across the heather moor in tides aligned with the seasons. They cross boundaries between estates on open hillsides, unmarked by fences or walls. In this way, each landowner’s actions impact directly upon his neighbours: if one shirks his duty in the annual cull, numbers across the whole region rebound. It is in their interests to cooperate, then, but with so many clashing views and beliefs, these so-called management groups often grow unmanageable.

Julien, my friend with the rifle, has been in charge of deer management on the East Rhidorroch Estate near Ullapool, a port on the north-west coast, for the last three years. Having come there as a backpacker, looking to work in exchange for accommodation and experience, he fell in love with the middle daughter of the owners, Iona, and together the young couple took over the running of the remote estate.

At first, a neighbour held the rights to stalk deer – and with it the responsibility for carrying out the culling – on their land, but when the lease for those rights came up in 2014, it seemed natural that East Rhidorroch should reclaim them. For Julien, who studied ecology as an undergraduate, it was an interesting way of applying what he had learned in class. Indeed, it was all around him here in the west Highlands, with herds of hinds and stags roaming the hills, and deer-stalkers in bloodstained tweeds riding by on their quad bikes. This was part of the culture of his adopted home – and wasn’t it one of the reasons he had found this place so enchanting?

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Inevitably, the reality turned out to be rather complicated. The responsibility of the cull proved onerous for an inexperienced Frenchman who had never before owned a gun. Highland ghillies are often born of stalking families, and have spent their whole lives in the hills. They know how the weather affects the deer’s behaviour, and where they are to be found come sunrise, come noon, come sunset.

But as hard as all of this was to learn, negotiating the politics of deer was harder. Twice a year, the couple are now expected to attend the meetings of their local deer management group – hours-long meetings, held in dreary hotel conference rooms, that never seem to come to a consensus. Last time, Iona tells me, there was more than an hour of fractious back-and-forth before they even got on to the subject of deer.

The sheer expense of it all has been another nasty revelation. Thousands just for the basic equipment: a £600 rifle, a £1,500 scope. A moderator to muffle the gunshot. The camouflaged hunting outfit in heathery tones: smock, trousers, heavy duty boots, balaclava. Training courses. A manner of transporting the dead deer home: by quad bike (£5,000), perhaps, or Highland pony. A game larder, where the meat might be hung and processed. And the days and days that might otherwise be spent farming sheep, instead now passed belly-down in the mud on the mountain.

To begin with, Julien couldn’t get it right, ruining his chances for a kill a different way every time. Walking upwind of the deer. Revealing himself on the skyline. His fingers quivering for too long on the trigger. Often he returned at dusk, empty-handed and so exhausted that at 4pm he would topple into bed and stay there until the rise of the low winter sun over the valley’s sides at 10am the next day, when he would head out all over again.

Facebook Twitter Pinterest Red deer at the Highland Wildlife Park, Kingussie, Scotland. Photograph: Murdo MacLeod/The Guardian

Then, on one of the coldest days of the year, towards the end of his first winter as a deer stalker, his efforts were rewarded. Heading out alone, camouflaged in a snow-white bodysuit, he finally attained invisibility. In a land of whiteness and silence, he became white, he became silent.

A group of 70 deer moved across the hillside, their eyes sliding past his motionless body in the snow, and came to surround him. “They were everywhere,” he recalls. “Playing and fighting. They had no idea I was there.” He lay like a rock in their midst, sizing them up. He spotted an elderly, underweight hind, a prime target, and steeled himself for action. Seconds passed. If I shoot, he remembers thinking, this beautiful moment will be over for ever. Then he pulled the trigger.

As a teenager growing up in genteel St Andrews, Mike Daniels dreamed of saving the world. He was “hippyish”, he says. Vegetarian. Keen to make his mark. When he was 16, he organised a period of work experience for himself at Creag Meagaidh, a nature reserve in the Cairngorms where woolly willow and saxifrage grow on a gilded mountain plateau; an enclave of dotterel and snow bunting and mountain hare.

On his first day, nervous and excited, he was picked up from the station and driven to where he would be staying, and as they got out of the car, they spotted a deer wandering in the woods nearby. Things moved quickly. The man who was driving leaped out and grabbing his rifle from the back. He shot the deer, gutted it on the side of the road, then lifted it on to the roof. “Blood was dripping down the windscreen,” Mike says. “That was my introduction.”

Though shocking for an idealistic teen, it was a fitting start for a career that has come to be defined by the difficult relationship between the demands of conservation and of the wild deer themselves. Mike sees a similar emotional journey in many of those who have since come to work with him in the field. “They think the deer are lovely, that Scotland is beautiful … and then they learn more about it.” Deer culls, he now believes – having seen the devastation they can wreak first-hand – are a necessary evil. A way of re-establishing the natural order.

In 2004, Mike was working for what was then called the Deer Commission when he and his colleagues were called in to conduct an emergency cull at Glenfeshie, an estate owned by a Danish billionaire in the Cairngorms National Park, where deer numbers had been allowed to grow to remarkable levels: an estimated 95 per sq km. Sharpshooters were flown in by helicopter to the estate’s remotest corners, and dozens of contract stalkers were bussed in for an intensive effort. Mike was in the larder, processing the bodies.

Altogether, more than 500 deer were slaughtered. The cull – the first state intervention on a private estate – created an enormous controversy. Animal rights campaigners accused the commission of acting illegally. Local gamekeepers staged a mass protest against the “carnage”, which, they said, went against “our way of life, our morals, our beliefs … and above all our respect for the deer”. Neighbouring landowners and local residents took to the airwaves to voice their disapproval.

Now, as the head of land management of the John Muir Trust, a charity dedicated to the preservation of Scotland’s wild places, Mike sees those same arguments playing out time and again. As the owner of several sizeable landholdings across the country, the conservation group has been using its power to manage the land in a way that prioritises the environment, specifically by preserving and regenerating fragments of the once-great Caledonian Forest.

To do so, they say, they must significantly increase the number of deer culled on their properties. The alternative – fencing off the vulnerable woodlands – is not an option. Mike sighs when I bring it up: “the F word”. He and the trust both see fencing as “treating the symptoms not the cause”, and it keeps the deer from seeking shelter in the harsh weather of the Scottish winter. They would rather reduce numbers so significantly as to render fences unnecessary.

However sound their reasoning, it does nothing to endear them to the owners of neighbouring sporting estates. Such an estate’s value is partly based on the number of stags available to shoot there each year – a good rule of thumb being around one in every 16 stags on the hill. And those who pay for the pleasure of shooting a stag (or far more, for the pleasure of owning a private deer forest) don’t wish to spend too long fruitlessly roaming the glens without a sighting. But though some estates do make significant income from slaughter tourism, they are in the minority. “It’s a bit like owning a football club. A small few – the Chelseas, the Man Uniteds – are big money-spinners. Generally, though, they run at a loss.”

A Highland truism: you don’t get rich from owning a deer forest; you own a deer forest because you are rich. Either way, the John Muir Trust’s no-holds-barred tactics have made them plenty of enemies. Sporadically, a new skirmish breaks out: in Knoydart, a wild western peninsula accessed only by boat, an argument flared up in 2015 when the trust’s stalkers shot dozens of stags more than their agreed target. Some, shot down in the most far-flung places, were left to rot where they fell, or to be picked over by the eagles.

Facebook Twitter Pinterest A red deer stag feeding on young birch trees. Photograph: Alamy Stock Photo

The language employed by protesters in these cases is emotive: those who conduct the cull are accused of “senseless slaughter”, of creating a “bloodbath”, or a “massacre”. To Mike, these slurs are hurtful and hypocritical: the numbers shot by the John Muir Trust are a fraction of the total culled each year across the country. And many of those levelling the charges are shooting deer themselves.

But the controversy speaks of a deep unease about mass killing among many of those who earn their living on the hill. The gamekeepers protesting at Glenfeshie were not parading their “respect” for their quarry for effect. A specialised strand of folk ethics has grown up among stalkers: the rules are based on perceived sportsmanship, on fairness, on tradition. To them, flying in by helicopter simply feels wrong, like cheating. So does leaving carcasses to rot. So does taking too many in one go.

At what point does a cull turn into a massacre? Big questions, these, to ponder as you stare down the barrel of a rifle.

In a grassy hollow behind the white-sand beach at Achmelvich – a tiny, remote village on the west coast – Ray Mackay, a crofter, lives in a wooden house overlooking a small green lochan dappled with waterlilies. I am sitting at his table, admiring the view, when he appears bearing tea and an A4 folder of grievances. He, and the Assynt Crofters’ Trust, of which he is vice chair, have been fighting an increasingly high-stakes battle with the government over the fate of the red deer on their land.

Their land: that’s the operative term. Back in the early 1990s, the Assynt crofters fought a different battle – a long one and a hard one – when they undertook the first community buyout of a private estate, raising hundreds of thousands of pounds to buy the land they lived on and worked from an absentee landlord with whom they had been wrestling for years.

The case of the Assynt crofters came to symbolise the many inequities of land ownership in Scotland, where just 500 individuals own more than half of the land, and where the pain of mass dispossession in the 18th and 19th centuries still echoes loudly in the culture.

The problem, says Ray, revolves around a remnant of old-growth woodland situated partly on their land. A governmental body, Scottish Natural Heritage, believes it to be at risk from overgrazing, and has advised them to undertake an emergency cull; the Crofters’ Trust disagrees, questioning the population estimates and pointing to abnormalities in the surveys. It is not just the principle of the matter, says Ray. They shoot deer for management reasons every year. For them, the issue is a matter of scale. If they accept the mass cull, they believe they could send the deer on their estate into a precipitous decline.

Facebook Twitter Pinterest A herd of red deer in the Cairngorms National Park, Scotland. Photograph: Alamy

The crofters have worked hard to escape their debts and to make the community sustainable. “We survived,” Ray says. “That was not a given.” Assynt is not a wealthy area. Small crofting townships of modest, whitewashed cottages and modern bungalows cling to the rugged coastline, linked by winding, single-track roads. The peninsula’s interior is an undulating blanket of peat bog: sodden, stony and ill-suited to agriculture. There are more deer here than people. He shows me the latest accounts: income from stalking and venison sales amounts to nearly a sixth of total profits. Here the deer are an asset rather than a hobby – this is no football team vanity project – and they do not intend to risk the depletion of this natural resource.

Last year the dispute with Scottish National Heritage came to a head. Having declined a voluntary cull, the crofters were threatened with a section 8 order – a forced cull. The crofters would be fined £40,000 for failing to manage deer numbers responsibly, and would have to pay the costs of the operation – a sum that would likely far eclipse the fine.

For the government, such a move would be embarrassing: that these legal powers should be used for the first time against a community group that was once a cause célèbre and darling of the devolved parliament. The dispute gathered column inches; the crofters’ chairman swore that they would go to jail rather than comply. In the end, Scottish Natural Heritage backed down. A compromise agreement that would be acceptable to both crofters and conservationists is still being hammered out. Of all the outcomes, it is perhaps the best one. But it has been an exhausting, frustrating process for all those involved.

There is a certain class of conservationist, says Ray, who are very keen, and their hearts are in the right place – but at a basic, unarguable level, they are usually incomers. When they drive in, making demands, it immediately sets up a tension. “The undercurrent is that they seem to be saying that we are not managing our environment as well as we could. But this is the place where you find the wild cats. The black-throated divers.”

He tells me about a map recently drawn up by the government, which identified the trust’s North Assynt Estate as one of the country’s most extensive areas of wilderness. I nod unthinkingly in approval, picturing the grand, curving aspect of the Assynt landscape. It is a stark, treeless place where golden eagles flash over a wind-scoured moonscape of moor and blanket bog.

“But these are our common grazings!” cries Ray. “One day they decide it to be ‘wild land’, but for us it’s where we work.”

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His words recall the writing of the environmental historian William Cronon, who wrote in 1995 that “far from being the one place on Earth that stands apart from humanity, wilderness is quite profoundly a human creation”. To the untrained eye, the wide-open spaces of Assynt appear an untamed, untameable land. To its occupants, they are laced with human history.

Seen through this prism, the question of what is natural and what is unnatural is a tangled one. Is the proliferation of deer the result of human meddling? In all likelihood, yes. Do we then take responsibility for removing the excess, for returning the land to an equilibrium more in line with what went before? What is the better course of action? What is more moral? What is more natural?

This is an extract from Winterkill by Cal Flyn, published in Granta 142: Animalia. Go to granta.com/guardian for a special Guardian subscription offer with a 25% discount

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