Fitbit and other ‘activity trackers’ can be used to calculate the energy you use walking to work, climbing stairs and (quite often) just sitting still. They are the latest generation of wearable tech encouraging us to expend more and consume less energy. By attaching similar devices to polar bears, scientists have observed how they divide their time and energy in the Arctic, an environment where every calorie is crucial.
‘Polar bears are spending as much as 70 per cent of daylight hours resting,’ says Anthony Pagano, research biologist and principal investigator of the study by the US Geological Society. ‘Another 15 per cent is spent walking and the last 15 per cent on all other activities such as hunting, eating, swimming and socialising with other bears.’ The results were collected in Alaska over spring 2014 and 2015 by fitting seven adult polar bears with a small camera and locator device. The footage was used to deduce averages for time spent doing certain activities.
While 70 per cent may seem like a lot of time to rest during the day, the downtime is crucial for the polar bears. They hunt approximately every ten days, so their energy has to last. ‘They also have unusually high energy demands compared to other mammals,’ says Pagano. ‘This is probably down to a combination of factors. Firstly, they’re big – the biggest terrestrial mammal on Earth – and energy demands increase with body size. Secondly, they have to navigate a varied topography – they swim in cold water, haul themselves up onto the ice and walk long distances to find prey.’
The study highlights the survival issues polar bears face in a changing Arctic landscape. ‘Ideally, polar bears “still hunt” on the ice,’ says Pagano, ‘using as little as energy as possible, they sit on the ice and wait for seals to come up to breathe.’ However, as Arctic ice breaks up sooner, the bears are forced to walk longer distances following its retreat northwards, or to chase less energy-dense foods such as birds and their eggs on land. ‘It is likely that declining ice is causing them to expend more and consume less energy,’ says Pagano. ‘Not meeting their high energy demands could be part of their decline.’
Pagano will resume his study in spring this year when he hopes to also use accelerometer devices to observe the animal’s night-time behaviours.