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
It is actually rather efficient for certain species.
If a species regularly has batches with multiple offspring or if they reproduce a couple of times in a year – then yes, infanticide makes sense in that there will be more resources for the surviving babies. You want to have viable offspring, but if a couple turn out sickly or weaker ones, or ones who aren’t able to thrive as quickly then its better they are sacrificed than the stronger ones having to struggle for resources. Things I’m talking about here would be alligators/crocodiles, some birds, some mammals, etc.
It’s also strategic to have as many as possible in certain cases because of a higher die off rate. Again crocs/gators are a great reference. Not all of the eggs will hatch. Plus, their young are prey for other animals. Thus, higher numbers are good to start with. But if resources aren’t available then infanticide may be necessary.
It would be rare to seen infanticide among, say, elephants, deer, cats, etc. The first two rarely have multiple offspring per birthing.
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