On November 30, British Columbia will introduce a ban on the trophy hunting of grizzlies. Sarah Marshall ventures into the Cariboo Mountains to meet Gary Zorn, an ex-hunting guide who pioneered bear tourism in the province.

Wading through waist-height devil's club shrubs with leaves the size of dinner plates, I feel like a shrinking Alice in Wonderland.

Everything around me is enormous.

Towering until they almost block out the sky, colossal cedars and hemlocks create a comforting sanctuary, securely grounded by their ancient roots. For a relatively young country celebrating 150 years since Confederation this year, these 400-year-old beauties are treasured historical monuments.

In Canada, everything is supersized: distances are vast, forests are endless, and wildlife is wonderfully abundant. It's a scale almost incomprehensible to someone from a small European island which could probably fit neatly into the pocket of west coast province British Columbia.

And if the sights are big, the sounds are even bigger: The grumbling of a sore-head sleeping grizzly disturbed from his slumber echoes around the forest canopy like a rumbling storm about to break.

Frozen to the spot, his eyes darting wildly, Gary Zorn shhs a wrinkled index finger to his appropriately ghost-white beard. A seasoned guide, with 40 years' experience trekking bears in this area, he's not afraid, he's simply listening and anticipating what the grumpy grizzly metres away from us might do next.

Originally a tracker for hunters, 71-year-old Gary is a master of bear behaviour, but early on he made the decision to swap guiding guns for leading wildlife tours, and is one of British Columbia's true pioneers.

On November 30, the trophy hunting of grizzly bears will be banned in the province, a decision welcomed by many and supported by the economic growth of nature tourism, proof these animals are worth far more alive than dead.

"Hunting was becoming a dirty word," explains Gary on his initial decision to change tack. "But when I told friends ecotourism was the way forward, they laughed at me." Firmly resolute, he carried on and was granted the wildlife guiding permit 001, the first to be issued in the province.

Based at Pyna-tee-ah lodge at the base of the Cariboo Mountains, deep inside BC, he runs Ecotours BC with his wife Peggy, operating almost exclusively in an area the size of Switzerland. Combining boat trips along salmon-filled rivers, active treks through sub-Alpine forest and even (on occasion) heli-hikes to peaks above the clouds, he promises wild, intimate but always respectful encounters, deservedly earning him the moniker 'Bear Whisperer' - a title he's trademarked.

A cloak of foggy drizzle sweeps across the Mitchell River, a tributary of the Quesnel, on our first outing, an 80km speedboat ride from the lodge. Birds of prey swoosh through webs of mist netting the tips of fir trees and beads of rain hang from garlands of lichen like jewels.

Next summer, Gary plans to launch an ambitious glamping site in this remote, peak-fringed wilderness, with smart safari-style tents pitched on a floating platform. Dawn and dusk brown bear viewing will be possible, with days spent exploring caves by kayak and hiking through ancient forest.

Thousands of sockeye salmon return here from September to October, firing upstream like silver bullets until they mutate into plump, green-gilled, devil-red monsters, travelling from the Pacific Ocean before spawning and dying in the place they were born. They're a bedrock in the food chain and provide a particularly tasty meal for bears.

Wearing waders almost up to my chin, I climb over a chaos of toppled trees and decrepit branches, squelching salmon carcasses underfoot. Dragged by bears from the water, their nutrients are responsible for the forest's epic growth spurts; salmon DNA has even been found in cedar trees.

Gary ushers our group of four (the maximum number of guests per outing) to a log jam on the water's edge, and sitting with our legs dangling in the aquarium-clear stream, we wait.

It's about an hour before the first diner turns up, a hulk of a bear stripping fish as we would a banana. "Will you look at the foot on that," gasps Gary. But one whiff of our scent, and the grizzly is gone.

It's been a difficult year for bears, our guide explains, as we head back to the lodge, wending past forest-swathed ridges baring conspicuously gaping scars. This summer wildfires ripped through the province, destroying more than 11,000 sq km of land. Although bears are resilient, the smoke and stress had an impact.

"In all my years, I've never seen anything like it," exclaims Gary, who noticed the grizzlies were becoming almost nocturnal to avoid the heat.

Suddenly, mid-conversation, he switches off the motor, as a female bear with cubs bounds angrily towards us. "Aggie," sighs Gary, with a degree of fond familiarity. "That bear never liked me."

Acquainted with many since they were cubs, Gary knows most of the bears in this area. Au fait with their physical features and mannerisms, he can connect the different families and is convinced they recognise him, too.

A real storyteller, he has the dinner table spellbound later that night with recollections of humorous and high-octane adventures, all delivered with a lyrical intonation that ebbs and flows like a warm wave.

There's the tale of a raven who helped a deaf bear find his dinner (the clever bird knew he could feast on leftovers); the suspense of a stand-off with a curious sow (waving his arms and growling helped our protagonist escape), and the remarkable account of a wolf chasing a fawn over Gary's head (almost too ridiculous to tell).

Leaning over and whispering, Peggy reveals her husband keeps a journal every night, with 30 years of observations noted down. "Most of the things he knows, you can't read in a book," she says with pride.

His findings have been shared with a trusted few, including Ryan Simmonds, who came to work as a guide for the Zorns four years ago. While Gary takes care of the river activities, animal enthusiast Ryan is largely in charge of hikes. He's inseparable from Penny, an energetic Border Collie who's been trained to detect the whereabouts of bears, moose and wolves, but will never give the game away by barking.

In autumn, silver birch trees flutter coyly in their golden fineries and hillsides radiate a spectrum of burning colours. Following a spiral of logging trails, we wind towards the top of Mount Brew, where footprints from a large male bear have been seen.

"If you want to understand wildlife, you need to simplify your thinking," says camo-clad Ryan as we embark on a steep, sweaty hike through huckleberry bushes and sub-Alpine firs. "We're the ones that overthink things."

Arriving at an opening sprinkled with snowdrops of cotton grass, I'm struck by the overwhelming silence. There are 250 species of birds in the Cariboo Mountains, but until the honeyed morning sun hits these peaks, not one is audibly present.

Instead I settle for the intoxicating scent of sweet pine and views of quartz islands shimmering in a nearby lake.

Only when we return to our vehicle do we encounter signs of life: a mound of bear poo topped with glistening undigested berries is an invitation for scavenging squirrels and chipmunks to tuck in.

There may be no bears but I'm acutely aware of their presence. They're probably watching us, laughing at our human clumsiness from afar.

The final insult comes when we notice fresh paw prints in the muddy ground, planted over our own steps made earlier that day. Crushing our tiny strides, they belong to a giant. But in a country where size is everything, I shouldn't be so surprised.

TRAVEL NOTES

Ecotours BC (ecotours-bc.com) offer several different full board packages, depending on the time of year.

For more information on the destination, visit explore-canada.co.uk and hellobc.co.uk.

Air Canada (aircanada.co.uk) fly direct from London Heathrow to Vancouver. An onward internal flight is required to Williams Lake.