"There's dinner boys," laughs Anne Todhunter, pointing at three moving shapes high on a steep slope. "Now go get them."
No one moves, apart from the animals which have clocked our presence. They bound across the rocky face and disappear round a ridge. Thar are like that, explains Anne's husband Philip - wary creatures alert to the threat that humans may pose.
The Todhunters own Lake Heron, a huge and spectacular property in the mid-Canterbury high country. Their core business is raising merino sheep and Angus cattle. In the last few years, they have added low-impact tourism to the enterprise.
Small guided groups get to share the back country which bears the stamp of successive Todhunter generations - either by mountain bike along rough metal roads or on foot via the paths that musterers have trod for decades. Trampers get easy or more gut-busting options - both trips offer alpine grandeur, braided rivers and a brush with the elements or, in our case, a nervy herd of thar.
To wander the backblocks with the Todhunters is to take a crash-course in exploration - a bit of settlement history, a shot of ice-age geology, a dash of natural discovery - all wrapped up at day's end with some quality vino and decent tucker.
Four of us have enlisted for a three-day highland hike. On this trip, Philip and Anne share the guiding duties. Before we head off, Anne - an accomplished mountaineer and qualified alpine guide - runs though our route and some safety advice. Philip, who in winter takes skiers by helicopter to Lake Heron's remote snowy basins, checks the tramping stove.
A cold front sweeping up the Main Divide means a late change of plan. Instead of easing into our trek, we're taking the hard-charging route.
"Okay with that?"queries Anne. We shrug, knowing we really don't have a choice.
The day is cool and clear as we head up Rough Creek, a boulder-strewn gorge with climbs of 600m over two hours. We cross and re-cross cold, tumbling waters, which flow over gaiters and seep into boots. Philip points out coal seams squeezed by massive forces which shaped the soaring valley walls.
A startled kea screeches out of beech trees. Two hours in, we reach a grassy clearing and pause for a snack. It is here that we spot the thar. Philip picks up the songs of a grey warbler and a bellbird. He explains the sunny, dappled glade is used by rutting stags as a wallow. We move on.
Before heading for a saddle high above us, we refuel on sourdough bread, cheese, sprouts and salami, while Philip fires up the portable stove for a brew. Anne gives us a crash-course in shingle scree techniques. The thing to remember, she remarks, is how to crouch in case rocks hurtle our way.
Up we go, stepping in each others' footprints. The crouch lesson is not needed. Twenty minutes later, we reach the saddle. Away to the west, the Arrowsmith mountains fill the sky. Beneath our feet, tiny mosses and lichens somehow survive in the desolate domain.
Our descent past stunted tree daisies, weeping dracophyllum and tough mountain flax takes a brisk 90 minutes. Shelter for the night is a quaint tin-clad shepherds' hut beside the glacier-fed Cameron River. Built in 1923, the "Highland Home" remains a sturdy refuge. Inside, it's been given a cabin-class upgrade. Our bunks are firm and comfortable, food is warmed on a gas hob (choppered in during the off-season by Philip) and heat comes from a pot-belly wood fire. We tuck into a lamb casserole, fresh beans and couscous, our faces lit by flickering candles.
Our big climb accomplished, the goal on day two is to reach New Hut, a mere seven hours away. Progress though the thick snow, tussock and painfully sharp speargrass is careful.
As we push over a ridge, ancient landforms unfold. Distinct lines along the vast valley slopes record the path of ice-age glaciers. Holes known as kettles left by retreating glaciers dot the landscape.
Soon we are reminded we are guests on a working farm when a startled flock of ewes put some distance between us. Inquisitive heifers, though, push towards our track as we skirt their paddock.
Late in the day, we reach New Hut. Our 90-year-old shelter has been given a 21st-century twist, with a polished concrete floor, ply walls, solar lights, gas fridge, stainless bench and a shower heated by the firebox. What this means is cold beer and wine to go with the Greek stew Anne dropped off a day or so before.
More thar are spied from a hut window. We gather and watch as a male, obvious from his shaggy mane, nudges his herd past rocks and scrub. They might be pests, and a threat to the fragile mountains, but are still quite splendid in the wild.
In the dead of night, an almighty din wakes the hut. Two possums are fighting on the tin roof. Anne is outside in a flash, throwing stones at the pests until they scurry into the darkness.
Day three is chilly and grey. Overnight snow is down to 1000m and the wind bites our faces as we trudge towards Prospect Hill, 900m above the Rakaia River.
The first creek we cross is running high. Linking arms, we push through the swift flow. Two hours on, we stop at Downs Hut which, unlike the others we've seen, is showing its age. Visitors to this rough and remote shelter have left their names on the tin.
Pat and Robin Todhunter came twice - on their honeymoon in 1935, then 50 years later to see if things had changed. Probably only their ages. In this special part of New Zealand, change treads slowly on the land.
Getting there: Air New Zealand flies daily to Christchurch.
Highland hikes: Station trips run from November until April. A good level of fitness helps and visitors should be prepared for all weather - you're heading into the mountains.
Andrew Stone was a guest of Lake Heron Station, Overland 4WD Rentals and Air New Zealand.