It’s one of evolution’s most brutal parables: male lions that displace a rival from his pride more often than not kill his cubs. Leonine logic and instinct dictate that energy is better spent preserving the genetic line of one’s own cubs than those of a dethroned adversary. Quickly dispatching his heirs speeds along that process by bringing their mother into estrus sooner.
Though it might seem counterintuitive in light of the infanticidal ways of other animals, gray wolves (Canis lupus) tend to do the opposite. New research out of Yellowstone National Park highlights an intriguing wolf behavior: When males take over a pack, either killing the dominant male, exiling him, or forcing him into a subordinate role, they usually adopt the existing cubs. Killing them would not prime their mothers for breeding — wolves come into estrus only once a year regardless — and the pack as a whole benefits from increased numbers, as the saga of the Wapiti Lake pack dramatically illustrates.
