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
In the case of birds, it is natural selection getting an early start. The parents kick the weakest or least likely to survive out of the nest. The initial egg production is a fraction of the energy cost of keeping a chick alive through fledging, so they are cutting their losses by focusing on the ones likely to survive. By having more eggs initially, they raise the chances of getting at least a couple strong chicks. The crab thing may be similar, I have no clue.
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