Bear question...

[caddisguy]

Hmm I was unaware there were more color phase in the west. Is there a major difference between north and south?

My understanding was that it was about open terrain. Brown phase bears are tougher to spot, at least where I hunt. That could mean they are more successful as predators (catching fish, deer, etc) as well as evading predators ... I wonder if temperature could be a factor too. I can't imagine wearing a few winter jackets in the summer let alone a black one. But east/west? I figured there is more open terrain in the east.

[boxhitch]

Many species of wildlife have signs of genetic separation linked back 10's of 1000s of years to the ice ages and how various mini freeze-thaw cycles caused migrations and isolations

[James52]

I'd say it all has to do with Natural Selection. In the east there is more thick, dark timbered areas (a generalization).....therefore some sort of selective advantage in being a darker colour (ie: black). Over time bears with black coats have a selective advantage over others with lighter coats and leads to a population with mostly black coats. In the west the same can be said....but for a lighter brown coat. Less dark, more open country (in general) produces a selective advantage for lighter coloured bears with a brown coat in certain areas. Over time and many generations this leads to a population with more brown phase bears. It would be interesting to compare brown phase populations within BC. I think there would be more brown phase bears in the interior than on the coast or island......but I do not know.

[Pemby_mess]

The theories proposed so far make some sense. However I think it's important to acknowledge that there is always a lot of genetic variability within a species that exists in spite of natural selection, and not because of it. That variability is present simply due to randomness in the process of sexual reproduction. If there was some period of isolation, we can expect these random variables to concentrate in one population over an other, as we know to be the case with the ice sheets in NA, but that is not necessarily due to a selective advantage. Not every stable genetic trait has yet been subject to a species-wide selective pressure. Nearly every mutation has the ability to serve as an advantage however, given the right circumstances.

[Pemby_mess]

I'd say it all has to do with Natural Selection. In the east there is more thick, dark timbered areas (a generalization).....therefore some sort of selective advantage in being a darker colour (ie: black). Over time bears with black coats have a selective advantage over others with lighter coats and leads to a population with mostly black coats. In the west the same can be said....but for a lighter brown coat. Less dark, more open country (in general) produces a selective advantage for lighter coloured bears with a brown coat in certain areas. Over time and many generations this leads to a population with more brown phase bears. It would be interesting to compare brown phase populations within BC. I think there would be more brown phase bears in the interior than on the coast or island......but I do not know.

I'd expect that as well, just based on my experience. But there are still geographic boundaries in place that create some level of genetic isolation. The two Coastal mountain ranges are significant ones. Any geographic boundary is going to increase the probability of population specific genetic differences.

[kootenaihunter]

I don't know about the credibility of the site, but it sounds like it's similar to what has been discussed so far...

https://www.bear.org/website/bear-pa...or-phases.html

East of the Great Plains, nearly all are black. These were the first bears early settlers saw, hence the name. The melanin in black fur makes the fur resistant to abrasion in the brushy understory of eastern forests. In forested states that border the Great Plains, 5% to 25% are shades of brown rather than black. About 5% are brown in Minnesota. Blond or white individuals are rare in Minnesota, but a young white male was seen near Orr, MN, in 1997 and 1998.
In western states that have mountain meadows and open park-like forests, over half the black bears (Ursus americanus cinnamomum) are brown, cinnamon, or blond. Light colored fur reduces heat stress in open sunlight and allows the bears to feed longer in open, food-rich habitats. The lighter colored fur may also camouflage them from predators in those open areas. Ice Age predators undoubtedly used to kill black bears in open areas where the bears couldn’t escape up trees. Grizzly bears still do that in some areas today.

[Fella]

I’ve heard it’s correlated with precipitation. More rain means larger population of black coloured bears, and more colour phase in dryer climates. Black bears would do better in wet areas as they would blend in better with the dark forests while phase bears would blend in better with drier areas due to being more open and brownish/gold vegetation.

[wideopenthrottle]

I would have said due to geography, ie population pockets in the mountains, there would be less genetic diversity allowing recessive traits to come out....

[James52]

I'd expect that as well, just based on my experience. But there are still geographic boundaries in place that create some level of genetic isolation. The two Coastal mountain ranges are significant ones. Any geographic boundary is going to increase the probability of population specific genetic differences.

I agree about your comments on geographic isolation and its relation distinct phenotypes within a species........(I am drawing on stuff I have not thought about in about 30 years....knocking off a lot of rust and dust....lol)

[j270wsm]

I’ve heard it’s correlated with precipitation. More rain means larger population of black coloured bears, and more colour phase in dryer climates. Black bears would do better in wet areas as they would blend in better with the dark forests while phase bears would blend in better with drier areas due to being more open and brownish/gold vegetation.

What about the " spirit bears " that inhabit a coastal island?