The polar bear that killed a British teenager and seriously injured four others was starving and underweight, experts say.
An analysis of the bear's 250kg carcass revealed that it hadn't eaten for a long time.
The survivors of the attack, who are now in a stable condition, have been airlifted back to Britain from Spitsbergen, Norway.
Scott Bennell-Smith, 17, from Cornwall, and Patrck Flinders, 16, from Jersey were taken to hospitals in England by air ambulance.
Meanwhile, team leaders Michael "Spike" Reid, 29 and Andy Ruck, 27, who were also mauled by the bear are set to fly out later today.
Reid, who was seriously injured around the face and neck after coming to assist the boys, shot and killed the bear.
He has been hailed a hero by the group, but tragically, he was unable to save 17-year-old Horatio Chapple, who was killed by the bear.
Liv Asta Odegaard, spokeswoman for the Governor of Svalbard, who examined the bear's body said: "It had a very thin fat layer and little content in its stomach,"
Experts say that the trip-wire set up around the teenagers' camp did not warn the campers about the presence of the bear – or create "bear flares" which normally would scare off animals, like polar bears.
"They were all sleeping in their tents. It took them by surprise," Ms Odegaard said. "It is now clear that the bear had entered the tent camp at Von Postbreen glacier unnoticed."