![]() ![]() But heterozygous black wolves, being only a little less aggressive, do well on balance in areas prone to distemper outbreaks. The disadvantage of low aggressiveness may be too great for homozygous black wolves, despite improved immunity to distemper. ![]() In wolf society, that’s not a good thing, for wolves need to be able to defend their territory from trespassers. Both heterozygous and homozygous black wolves are less aggressive than gray individuals, and homozygous black wolves are the least aggressive. If it’s good to have the mutation on one chromosome, why wouldn’t it be even better to have it on both? It turns out that black coat color is also associated with a behavioral difference. It’s interesting that homozygous black wolves are less successful than gray colored wolves. It seems that black coat color is merely along for the genetic ride through evolution because it is linked to a mutation that improves immunity. The mutated form does confer superior immunity to some infections diseases: Black heterozygous wolves showed higher annual survivorship following 3 distemper outbreaks than gray colored wolves in Yellowstone National Park. In other words, the target of natural selection is probably the difference in immunological activity between the normal and mutated form of the ß-defensin protein, and has nothing to do with coat color.Īnd there is evidence to support that idea. Given the role of ß-defensin proteins in the immune system, scientists think that the mutated form of this particular ß-defensin protein improves a wolf’s ability to fight certain diseases. Since black coat color itself is not a survival advantage, there must be something else about that mutation that benefits the animal. Captured by trail camera at the same site where the two black wolves appeared. This more typically colored Minnesota wolf sports shades of gray, light brown, and cream in its coat. Some directly kill microbes, some influence signaling between different types of immune cells, and some do both. They also play a role in the immune system. But ß-defensin proteins are involved in more than just coat color. A single mutation in a gene coding for a certain ß-defensin protein enables that protein to bind to the Melanocortin I Receptor, and that causes black coat color. Since heterozygous and homozygous black wolves are the same color, there must be something other than coat color that gives heterozygous black wolves a survival advantage.Ĭoat color in dogs and wolves is mediated by a hormonal system called the melanacortin pathway. Homozygous black wolves, on the other hand, are less successful than gray individuals. Black coat color is a dominant mutation in a single gene, and only heterozygous black wolves fare better (live longer and reproduce better) than gray individuals. The answer is no, black coat color in and of itself does not improve survival and here’s how we know this. Why would that be? Does a black coat improve survival in some way other than camouflage? I learned that they aren’t particularly common in Minnesota, but they are more common in North America than in other parts of the world, and especially common in the Yellowstone area, where about half the wolves are black. That is a tiny sample, but I was surprised to get two of them and wondered if they are more common than I expected. I became curious about this when my trail camera stationed in a deer bedding area for a year in Minnesota captured 2 black wolves, out of 5 or 6 different individuals. This one and the other mostly black wolf pictured at the top of the page were captured by trail camera at the same site in Minnesota. ![]() Why would that be? The answer lies in an unexpected connection between wolf coat color variation and the immune system. But then there are black wolves – They are not as well camouflaged as gray individuals, yet they are becoming more common in parts of North America. In this way, survival is improved, increasing the odds of passing on one’s genes, thus enriching the gene pool with well camouflaged individuals. It’s easy to imagine how this evolved: Blending better with the surroundings makes them less conspicuous to prey animals, which makes it easier for them to capture dinner. For example, the white coat of the Arctic wolf allows it to blend better with the snow and ice, and the muted, earthy tones of gray, buff, and reddish-brown common in the coats of most other wolves allow them to blend with the vegetation in milder climates. Coat color varies more in the gray wolf ( Canis lupus) than in most other mammals, and some variations relate to camouflage. ![]()
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