The natural habitat of the white bear is a remote, desolate place, defined by extreme weather and ice-cold temperatures. No wonder then, that it can be hard to keep track of individual polar bears, which have been known to roam for thousands of kilometres, and even embark on epic swims that can last for days.
But in 2014, scientists made a breakthrough in their efforts to follow the activity of polar bears across the Arctic; rather then get closer to the animals, the solution was to monitor them from afar.
So far away, in fact, that they have begun to track bears from space.
Traditionally, scientists study polar bears by capturing and tagging them or by conducting surveys from the air, using low flying aircraft to spot the animals.
Such methods can provide a wealth of important information, but they can be disruptive to the bears and are often not possible in extreme weather or remote locations.
Satellite technology has the potential to open vast, remote regions of the Arctic to regular monitoring
So a team of scientists led by Dr Seth Stapleton of the University of Minnesota at St Paul, US explored a new technical approach.
Modern satellite imagery is now so good, seeing objects at a resolution of less than 0.5 metres, that it is possible to spot individual animals from space.
Previous studies used satellite imagery to estimate abundance at Weddell seal (Leptonychotes weddellii) haul-outs and emperor penguin (Aptenodytes forsteri) colonies in Antarctica.
In July 2014, Dr Stapleton’s team team published research in the journal PLoS One showing how polar bears could also be counted this way.
They secured images from a DigiGlobe satellite that imaged Rowley Island, in Foxe Basin, Nunavut, located in a seasonal ice region of the eastern Canadian Arctic.
Large numbers of bears aggregate on this island when the surrounding ice has melted.
Two independent observers scoured the satellite images for bears, both needing to agree on a sighting for a bear to be counted.
They then compared the sightings of polar bears from space with those conducted using conventional methods; including an aerial survey of the bears using a helicopter.
The different techniques consistently counted a similar number of bears, suggesting that counting polar bears from space could be an accurate, as well as convenient way, to estimate their numbers and movements. On occasion the space-based survey spotted bears that aerial surveys did not (see yellow circles in images above and below).
Both cloud cover and the conditions of the sea water can hamper the detection of bears from space. For example, foam can form on the surface of the sea, forming white dots that can appear much like a bear from such a distance. But overall, the technique seemed to work well.
“We think satellite technology has the potential to open vast, remote regions of the Arctic to regular monitoring. It has tremendous potential to aid the circumpolar management of polar bears,” Stapleton told the US Geological Survey, which helped facilitate the research.
By taking images at different wavelengths, the researchers also hope to improve the accuracy of the technique, as white polar bears look different to ice and snow at shorter wavelengths.