A recent study of 45 years of observational data about polar bears shows the animals hoard the bodies of kills, burying them in the snow or dirt so they can return to them at a later date.
The behavior, called caching, is relatively common in other bear species, especially brown bears, from which polar bears evolved around 500,000 years ago.
The behavior is exceptionally rare among polar bears, but Ian Stirling of the University of Alberta and the Scientific Advisory Council for Polar Bears decided to investigate after receiving an intriguing photo from a friend.
A team of scientists reviewed observational data of polar bears taken between 1973 and 2018, and found just 19 instances of a bear burying its kill after being unable to eat it in one sitting, a rare behavior observed in just 0.5 of bears
‘My curiosity about short-term food caching was re-activated by receiving a photo from a friend of a male polar bear lying on the ice with a mostly snow-covered harp seal,’ Stirling told Polar Bears International.
‘I had seen this kind of behavior only once in over 40 years of research on polar bears.’
For his study, Stirling reviewed observational data of polar bears taken between 1973 and 2018 in Svalbard, Greenland, and the Canadian Arctic, finding just 19 instances of kill caching from just 0.5 percent of the bears observed.
Polar bears live on a diet of mainly seal meat and can eat between 10 and 20 percent of their own body mass in one sitting.
The average adult polar bear weighs around 1,200 pounds, while adult harp seals weigh between 265 and 300 pounds.
The data reviewed consisted of video, photographs, and logs of bear behavior taken in the Canadian Arctic, Greenland, and Svalbard, a Norwegian archipelago in the Arctic
In rare instances when a polar bear was unable to finish eating a seal t had recently killed, it would sometimes bury it in the ground and guard the site from other predators, a common behavior among other bear species but one that’s rarely been documented among polar bears
This disparity means a polar bear couldn’t, or wouldn’t, eat an entire seal in one sitting only in rare circumstances.
When those rare circumstances do occur, polar bears will burrow into the snow or dirt to hide their kill, then cover it with snow or more dirt to make it difficult for any other bears who may happen by to pick out by sight.
Some bears were observed lying over their buried kills, unwilling to let them out of eyesight but also unable to eat them fully.