I was watching a nature documentary where a crab produced several dozen babies, and then turned around and started eating them. If she needed the nutrients so badly, why not just have fewer kids? From a thermodynamic standpoint that would preserve more calories.
I’ve also seen footage of birds brooding, laying, and then hatching multiple eggs, only to push half of the chicks out of the nest. That’s such a huge investment of time and energy. Why not just lay fewer eggs?
In other situations it is more understandable: A male lion might kill another male’s offspring to make room for his own. Cuckoos push other baby birds out of the nest so they can be adopted by the parents. But many cases of infanticide in the wild just seem time-consuming and wasteful.
In: Biology
They’re not falling for the sunk-cost fallacy. Sure it took a lot of time and resources to hatch all those eggs, but it also takes a lot of time and resources to actually raise those chicks to adulthood. If they have limited resources, they’re going to save themselves the effort of feeding all of their chicks in order to make sure the strongest ones get the best chance of surviving and reproducing.
A lot of animal behavior comes down to passing on their genes, and raising a bunch of weak chicks who will either die or fail to get a mate if they do survive isn’t conductive to that goal.
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