A single base pair. The stunning white Spirit Bear stands next to its pedestrian cousin.

What Makes a White Bear White

The brilliant white coat of the rare British Colombian Spirit Bear has long inspired wonder among those lucky enough to catch a glimpse of it. Now researchers have shown that a change in a single DNA base pair differentiates the famous bear from its ordinary black relatives. The gene analysis, reported in Current Biology, could help the Canadian government preserve the animals, only 100 to 200 of which remain in the wild.

The Spirit, or Kermode, Bear lives in island rain forests off British Columbia's coast and in adjacent areas of mainland Canada. Although its coat is almost entirely white, the Spirit Bear belongs to the same species, Ursus americanus, as the ordinary black bear.

To study the bear's genetics, Kermit Ritland and his colleagues at the University of British Columbia in Vancouver collected bits of hair that 22 white animals and 198 black animals left on trees and small traps in western British Columbia. Using forensic techniques, they isolated DNA for several known pigmentation genes from the samples. The team's focus soon turned to a gene for the melanocortin 1 receptor (mc1r), which tells certain cells to manufacture black and yellow pigments. A single base pair distinguished the gene in black bears from the gene in white ones. The change alters the mc1r protein, which stops the production of both pigments and leaves the animals white. Although the "white" version of the gene is recessive, black bears with one white gene and one black are uncommon. This may indicate that same-colored bears prefer to mate with each other, Ritland says.

The results should help the government protect the rare bears, says wildlife biologist Tony Hamilton of the British Columbia Ministry of Water, Land and Air Protection in Victoria. He says that the ministry will convene a group of conservation biologists to discuss the findings, which might be used to understand how newly proposed parkland for the Spirit Bear will affect its population.

Related sites

British Columbia government press release about the proposed Spirit Bear protection area
Ritland's Spirit Bear home page
Web site on the Spirit Bear, with many links

Posted in Biology