On Etorofu Island and Kunashiri Island in the northeastern part of Hokkaido, the only white brown bears in the world have been confirmed to inhabit.However, it is not known why white brown bears exist only on these two islands.A research group at the Research Institute for Humanity and Nature, Hokkaido University, who was investigating the cause of this, discovered that brown bears on Etorofu Island eat salmon more than three times as much as brown bears in Hokkaido.It was published in the academic journal "Biological Journal of the Linnean Society" of the Linnean Society of London.
White brown bears were found on Kunashiri Island in 2009, and only two islands, Etorofu Island and Kunashiri Island, have been confirmed to inhabit in subsequent surveys.It is also known that brown bears on Etorofu Island are larger in size than brown bears in Hokkaido.
A study of white American black bears, once conducted in Canada, found that white bears are less likely to be found in underwater organisms during the day and have a higher salmon capture success rate than black bears.From here, it was expected that eating a lot of salmon might be related to the body color and size of brown bears on Etorofu Island.
Therefore, the research group analyzed the elements that make up the skull of brown bears on Etorofu Island in the first half of the 20th century, which are stored in the Botanic Garden Hokkaido, Hokkaido University.I estimated what I was eating from there and compared it with the bears in eastern Hokkaido.As a result, it was found that the ratio of salmon to the food of brown bears in Hokkaido was 8.2%, while that of brown bears on Iturup Island was 27.3%, which is a food habit that strongly depends on salmon.
However, no white brown bears have been identified in North America, where there are as many salmon-eating brown bear populations as Etorofu Island.Therefore, the reason why white brown bears inhabit cannot be explained only by "eating a lot of salmon", but it is possible that individuals with a body color that is advantageous for catching salmon were more likely to survive.In the future, in order to completely unravel the mystery, we will proceed with research on the food ecology of brown bears and population ecology research such as what kind of genetic background there is.