New research made on wolves in North America showed that black wolves have antibodies for canine distemper, meaning they had the disease and survived. In wolf populations that suffer from canine distemper, the gray female wolves tend to pick black male wolves for mates, giving their cubs a chance of surviving canine distemper by receiving the gene from their father.
Photo by: https://www.pexels.com/photo/black-wolf-in-blurred-background-7715438/