Q: How do you measure a 110-stone polar bear? A: Very carefully!

But thanks to a powerful tranquilliser dart, this scientist, deep in the icy wastes of Alaska, was able to do just that.

Just a few minutes after being struck by the dart, and roaring with surprise, the angry male bear collapsed on the icy ground, unconscious.

1. Alert to the intruders: The polar bear spots the research team

But why go to such lengths to fell the bear? Well, a small team of intrepid scientists are compiling the vital statistics of all the polar bears in this area of Alaska for Project ThermoSTAT, a campaign that is drawing attention to the plight of polar bears and the threat posed to their shrinking environment by global warming.

With only 20,000 to 25,000 polar bears still existing in the wild, their task is vital.

To conduct their studies, the scientists quickly lay out the tranquillised bear in a spread-eagle position. The skull is measured, before the length of the bear is noted, using a traditional tape measure. Male polar bears, on average, are between eight and 10feet tall, while females usually come in between six and eight feet.

2. Bullseye: The team hit their target and the 110-stone polar bear falls to the ice

3. It's a knockout: A few minutes after being struck, the bear is unconscious

Weighing the bears, though, is a rather more awkward process. While two men using a weight bar were able to lift and weigh the 26-stone female bear they had tranquillised earlier in the day, they need to erect a special portable block-and-tackle hoist to take the measurements of the much larger 110-stone male.

Having recorded this bear's weight, next on the list is the jaw. With 42 teeth and a bite force that rivals the great white shark, the polar bear is not only the world's largest land predator, it is the wild's only fully carnivorous bear, with teeth perfectly designed to rip the flesh of seals apart.

While their primary prey are seals, polar bears have also been known to eat walrus and beluga whales, along with reindeer and birds.

The polar bear is a superb hunter  -  creeping up on its prey from behind, even covering their conspicuous black noses with their paws while hunting, to disguise themselves against the snow.

4. Lengthy: The researcher measures the length of the male bear

5. Hoisted: The bears is weighed with a special block and tackle

The bears can live off fat reserves for months at a time and have such a low body temperature (they overheat at more than 10C) that they are almost invisible to infrared cameras.

Clean and sharp, this bear's canine teeth are pristine. A small numerical tattoo is quickly branded in the mouth of the bear which will enable it to be identified in the future, before it is time to check his claws.

Short and stocky, the bear's claws are designed to dig into the ice and are scooped on the underside in order better to equip them to burrow deep into hardened ice.

6. Big head: A skull measurement is taken

7. Marked: The bear's lip is tattooed for identification

Once the final measurements are taken, a large identifying number is painted with temporary paint onto the bear's back, so that it will not be picked up again during the current survey. Then the team quickly pack up and move on to a safe spot.

Polar bear biologist Dr Steven Amstrup says tracking the bears is vital for their survival. Dr Amstrup hopes these pictures will help people to realise how special this species is and how much it needs to be protected.

Back on the ice field, the woozy, paintcovered and newly tattooed bear slowly rises to its feet. After a few tentative steps it is on its way, completely oblivious to the hazardous encounter that has just occurred.