Of the eight satellite tags the BBC saw attached to walruses in April, seven now appear to have stopped working.

Project leader Erik Born said the tags were probably expelled as the walruses' hides began to heal or they could have been knocked off by the thick sea ice.

The remaining working tag is attached to a female who has a calf in tow.

There is a chance that some of the tags may start sending data again, but I am not so sure about this Erik Born, project leader

So far, she has remained close the area where she was tagged.

Dr Born, a biologist at the Greenland Institute of Natural Resources, said: "There is still a lot of ice in this area, and she will probably stay there until the ice begins to retreat.

"But we hope she begins to move soon while the tag is still working. She should begin migrating any day now, but we could be unlucky if the ice remains."

Dr Born said he was a little disappointed that the rest of the tags had stopped working.

He said: "This year we tried a new smaller tag that we were hoping would last for longer, but this does not seem to be the case.

"Walruses have a very rapid healing process, and I think the tags are being expelled as their hides are starting to mend. They might also have been knocked off as the walruses were hauling out o­n to the ice.

"There is a chance that some of the tags may start sending data again, but I am not so sure about this."

The tagging study is being run by the Greenland Institute of Natural Resources, in cooperation with the Danish National Environmental Research Institute and the Technical University of Denmark.

MIGRATION MAP Walrus 1: Male, 4-5 years Walrus 2: Female, 10-12 years - has yearling calf in tow Walrus 3: Anomalous data Walrus 4: Male, 5-6 years Walrus 5: Male, 18-20 years Walrus 6: Female, 5-6 years Walrus 7: Male, 5-7 years (No data yet received from a tagged female and her son)