Remarkable footage of polar bears captured by the Arctic mammals on GPS collar-cams has given scientists a very rare glimpse into the bears' daily life.
The video gives a bear's-eye view of the world as they hunt for seals and has been released as part of a wider study into the impact of climate change on polar bears.
United States Geographical Survey researchers found melting Arctic ice caps may have bigger repercussions for polar bears than had previously been thought.
Scientists discovered the bears have higher metabolisms than was believed and they are finding it harder to find enough food to keep up their weight in their changing environment.
Using the cameras, researchers tracked nine female polar bears during 10 days in spring over three years.
They also took blood samples from the bears at the beginning and end of the study.
The data found polar bears need to eat at least 12,000 calories a day, which means capturing a seal every 10 to 12 days.
Of the nine bears the scientists followed, more than half lost weight. Four of the bears lost at least 10% of their body fat.
The study found the problem was compounded by the considerable amount of energy the bears used walking. The camera-wearing bears were shown to spend up to a quarter of their time trekking across the Arctic.
With more sea ice thinning earlier in the year, seals are becoming harder to find in spring - the bears' prime hunting season. As a result of the earlier melts, polar bears are being forced to walk even further and so burning more calories.
George Durner, United States Geological Survey said: "Things are likely to get worse before they're going to get better."