This young bear was injured, possibly in a fight with another polar or trying to kill a walrus. (Pictures by Tim Earl, 1028763)

THE Earth’s curvature reduces as one approaches the North Pole – and it is visible.Nudging through pack ice at 81 degrees north we were aware that the vista was flattening – a strange sight, as if the world had been altered somehow.

Most on board our ship were not interested in the flattened horizon, however. They were on a polar bear hunt.

With two tour leaders and some sharp-eyed guests to help the ship’s four wildlife guides, we saw plenty of bears.

These were the real thing: hungry polar bears on the ice hunting seals – and one another, once.

I had seen polar bears in Churchill, Canada, where they walk the beaches of Hudson Bay in October waiting for the ice to form as winter sets in.

Hungry but unable to hunt seals, they sleep a great deal or pace the water’s edge looking for any scrap of sustenance, even eating seaweed.

Dangerous and yet rather sad, they are watched by eco-tourists from tundra buggies – big buses with wide tyres to avoid hurting the delicate habitat.

Up in the pack ice north of Spitsbergen, the bears are in full hunting mode, sensing the air repeatedly, sniffing for the telltale signs of sleeping seals that could be three kilometres away.

Harp and ringed seals haul out onto the ice to give birth, care for their pups and sunbathe between feeding sessions.

The holes are kept open for a swift getaway should the world’s largest land predator approach.

I had always imagined that the bears hunted across the ice, stalking from downwind, using their off-white fur as camouflage as unsuspecting seals were targeted.

It is not always so. We saw one bear slip quietly into the sea and dive under an ice floe. It came up with a seal in its jaws, having approached the sleeping animal through its own escape-hatch ice hole.

Once killed, the seal was devoured rapidly. Other bears would have detected the smell and daylight robbery is always a possibility. (It is light for 24 hours a day up there in the summer.)

The kill attracted ivory gulls, one of the most difficult-to-see birds in our part of the world. Extremely rare in Britain, they spend their lives following polar bears to clean up scraps left from the gristly meal.

One was in Suffolk as the new millennium approached and I had planned to go there to ‘twitch’ the bird, but a firework display on New Year’s Eve scared it off and our trip was cancelled.

Polar bears are considered to be marine rather than land predators by some authorities.

This polar bear slips quietly into the sea and dives under an ice floe in its search for sleeping seals. (1028761)

They are certainly at home in the sea making long journeys across open ocean and shorter ones between rafts of pack ice.

Out of water, they have a tendency to overheat beneath the thick and highly efficient layers of fat that insulate the animals from intense Arctic cold.

One young bear found sleeping on the ice was injured, with wounds on its belly and right hind leg, perhaps as a result of fighting with other bears or possibly a walrus.

We had been watching it for some time before the bear sat up, licked its wounds and then sniffed the air, as if starting to hunt.

This was not its intention, however. It had detected another bear approaching and quickly beat a retreat, slipping into the sea and swimming off across the ship’s bows and onwards into deep pack ice.

Observers on board were not aware of its alarm at this stage. It was only after another older, bigger bear appeared following the first that we realised this was a serious chase.

Polar bears will kill each other in territorial disputes and sometimes if the victim is injured. The young bear was fleeing for its life.

It seemed to be doing a good job as we had increasing difficulty in spotting the animal in the gaps between ice floes.

Our 10-day cruise called at many places as we circumnavigated Spitsbergen – old whaling stations in the main, but a few mining sites, too.

Each involved wet landings on which we jumped into the sea from dinghies, wearing rubber boots, of course.

Our activities were dominated by polar bears, however. As the ice retreated in the Arctic summer, so bears were forced onto the land. Once ashore they hunted reindeer and seabirds, raiding the highly populated colonies of gulls and auks.

These are never sufficient to satisfy the animals and humans have a definite place on their menus. One mistake by our on-board guides and we would become bear-bait.

Before landing, the sites were scoured from the ship as our guides (and us) looked for bears. Any sign of one and we did not land. That rule was absolute and applied on a number of occasions.

So, too, was the one that should a bear be spotted once ashore, even at a distance, the visit was cut short and a swift but organised evacuation would take place. This occurred on two occasions after bears suddenly appeared.

One was spotted far away, feeding on what appeared to be a dead walrus. We returned to the ship, which then motored around to where the bear had been seen and we approached the shore in dinghies.

My height came in useful as I was deployed to stand and look for the bear, which was no longer at the long-dead carcass.

I spotted her behind a shingle bank and the boats were manoeuvred so that everyone could see.

The creature was in a poor condition, scrawny from starvation. We left her to make the most of her find.

A total of 20 bears were seen during the cruise, including one female with a quite small cub. Some, still riding the pack ice, were scores of miles from land, earning polar bears their title: kings of the high Arctic.

l Next month – I am the walrus: coo-coo-cachew, whales and Arctic foxes in the second part of Tim on tour to the high Arctic.In the first of a two-part series, Tim Earl is in Pole position as he searches for the world’s largest land predator and king of the high Arctic – and in his quest to see a polar bear first-hand has a couple of all-too-close encounters…