Over the past few weeks, two different mother bears at Brooks River have killed cubs that weren’t their own. So what would drive mother bears to kill another’s cub? If this mingling continues, an unrelated cub can end up nursing, seeking protection, or otherwise drawing on resources meant for the mother bear’s own cubs. During times of scarcity, mother bears might become increasingly intolerant of adopted cubs intermingling with their own. When the food supply dwindles, mother bears look out for their own.