One in every ten thousand or so human males either kills other human beings for pleasure or would if they could. This may be specific to humans, but I wouldn’t

One in every ten thousand or so human males either kills other human beings for pleasure or would if they could. This may be specific to humans, but I wouldn’t be too surprised to find that there are serial killers in other species. Or rather, would-be serial killers, because without tool use an animal would have to be a freakish outlier not only in terms of “psychopathy” but also in size and strength to be able to afford expending energy to kill another member of their species for no good reason.