Grizzly Bear

Photograph by John Eastcott and Yva Momatiuk

There's no getting around it: Male grizzly bears make bad dads. Male grizzlies take no part in the rearing of their offspring, which would be excusable if it weren't for another trait: They will kill any grizzly bear cub they find within their range on the off chance that the baby is not their own. Theories abound, but scientists are at a loss to explain this infanticidal behavior.