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
There’s a couple of possible situations where this becomes an evolutionarily stable strategy (if I may use jargon to hide from the squeamishness).
One is if the animal doesn’t know, at the point of conception, what resources will be available later. In that case, an animal that holds back and fertilises only a few eggs will miss out if conditions are good later; on the other hand, the one that fertilises a lot of eggs at least gets some of the calories back.
Another is that if the animal lays and hatches more eggs than they can support, then they can pick and choose the most promising ones to survive. If they lay just enough, they are leaving that to the genetic lottery, and might end up with fewer adult offspring than would be optimal.
Latest Answers