The three explorers taking part in the Catlin Arctic Survey have found their first polar bear tracks.

The team, which is co-sponsored by Green Guardian, came across the tracks of what they believe to be a big, adult bear on Friday.

Despite the dangers posed to them by the bears, the discovery boosted morale.

The trio has been battling for days to cross an ice rubble field, dragging their sledges up and down massive chunks of ice amid winds of 30 knots.

Martin Hartley, the team’s photographer, has also been struggling with an open blister on his foot. He has had to treat the wound every few hours – not an easy task at -35C.

“Our spirits were lifted (and the hairs on the back of our necks stood up!) when we saw evidence for the first time that We Are Not Alone out here,” wrote Pen Hadow, the expedition leader on his blog.

“We are visitors in a very special place.”

But morale dipped again on Sunday when the first flight to resupply the team had to be abandoned. The pilot could not see the airstip they had identified due to cloud cover.