What is a spirit bear?

How these pale-pelted mammals turn their colouring to their advantage

Image credit: Maximilian Helm

Species: Kermode bear

Ursus americanus kermodei

Size: Weight: 80–200kg, Length: 1.2–1.9m

Habitat: Found only in the Great Bear Rainforest, these bears build their winter dens beneath the forest’s dense canopy.

Diet: A spirit bear’s main source of food is fish, in particular Pacific salmon. Like all black bears, spirit bears are omnivores and therefore will eat fruits, nuts, plants and even carrion (rotting flesh) when fish is in short supply. Scientists think their white coats act in their favour when hunting for fish during daylight as they are harder for the fish to spot above the water.

Lifespan: 25 years in the wild

Threats: The biggest threat to this unique bear is disruptions in the coastal ecosystem. Declining salmon populations, tree logging and migrating grizzly bears could threaten this isolated species.


 

If you go down to Canada’s Great Bear Rainforest, you’re sure for a big surprise. Located at British Columbia’s northwestern coast, Canada, are dense forests spanning 21 million acres. Aptly named the Great Bear Rainforest, this Amazon of the north is home to some truly unique bears. American black bears are among the most common species, however only in the Great Bear Rainforest have these bears evolved with a different coloured coat. They are known as Kermode, or ‘spirit’, bears.

Traditionally sporting black fur, it’s estimated that there could be as few as 100 left. The change in colour is thanks to a rare genetic variation in a gene called MC1R, which codes for a protein that sits on the surface of melanocytes, cells that produce melanin for colouration. This mutation in the gene is what causes the melanin to appear white instead of black. Though these bears are often mistakenly thought of as being albinos – when there is a lack of melanin in the fur and eyes – this is not the case, as like black bears, they have a dark nose and paws.

Researchers have found that thanks to their unusual appearance they are 30 per cent more effective in hunting during the daytime compared to their darker counterparts. This efficiency may have been one of the reasons they have maintained their genetic lineage since the mutation was first expressed. It is thought that due to the isolated nature of the forests the gene has not spread further than the bears residing in Great Bear Rainforest. Another explanation for their continued presence has been selective mating, meaning that spirit bears have a preference for other spirit bears and so the genetic mutation is passed down from generation to generation.

Creating a spirit bear

What is the likelihood of a bear cub being a black or spirit bear?


This article was originally published in How It Works issue 122


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