I am told that there are some species, like fish or rabbits, that if let, will eat their own children. If this is true, how does a species like this exist? Shouldn't the fact that they kill their own lineage make them nonviable?
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$\begingroup$ Just keep the offspring away from the hungry adult. $\endgroup$– theforestecologist ♦Commented Mar 27, 2017 at 17:42
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1$\begingroup$ You assume there are many chances the parents individuals can even meet their offspring. This doesn't hold true in a variable environment like the one most species in Nature normally live in. I will give you one simple example. When I was a child I had an aquarium with little tropical fishes in it. In this closed space (non-natural environment) the very parents ate their own children when they were still very yound and no child fish could get to adulthood. However, if these very same fishes were living in Nature-like in some small river or marsh or any other natural pond, $\endgroup$– Yordan YordanovCommented Mar 27, 2017 at 17:48
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1$\begingroup$ their youngsters wouldn't even had the chances of meeting their parents (and being eaten by them) because immediately after hatching the small fishes would have gone into hiding among the vegetation in this natural pond and because they re small enough to hide easily they would most likely never have met with their parents (and thus avoid being eaten by them). There are many other similar cases with other animals where the hatchlings are so small they virtually live in other environment then their parents live in. $\endgroup$– Yordan YordanovCommented Mar 27, 2017 at 17:52
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2$\begingroup$ Rabbits (at least in captivity) will only eat their young if there is a protein shortage. Obvioulsy, any aminal that eats its young doesn't eat all of them. $\endgroup$– anongoodnurseCommented Mar 27, 2017 at 18:59
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Yes, it is true.
Prairie dogs
Prairie dogs for example are known for frequent infanticides.
Many other species kill their babies too
But of course, such behaviour also exists in other lineages such as grey langurs, gerbilles, lions, giant water bugs and Bottlenose dolphins (just to cite a few examples).
How does that evolve
It will be impossible to provide a complete universal explanation to this behaviour because the evolutionary processes causing this behaviour varies from lineage to lineage. For examples, in lions, only males kill young of the females that are still nursing and they do so when taking over a new harem only. In prairie dogs, mothers cause infanticide preferentially on others' babies but also on their own babies.
Going into the details of how such behaviour evolves in every specific lineage would probably require writing an intro on kin selection and other fields of evolutionary biology which is way too much for a single post. You may want to have a look at the wikipedia article infanticide for a start.
Shouldn't the fact that they kill their own lineage make them nonviable?
Of course, they don't kill all the babies. Only a fraction of them!
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"In prairie dogs, mothers cause infanticide preferentially other babies but only its own babies."- Could you rephrase that? I'm having trouble understanding which infants the prairie dog mothers tend to kill. $\endgroup$– HarrisCommented Mar 29, 2017 at 13:58 -
$\begingroup$ @HarrisWeinstein Thanks for noticing the typo. Fixed! $\endgroup$– Remi.bCommented Mar 29, 2017 at 15:26