Most animals don’t actually fall into the “pure herbivore” or “pure carnivore” categories. Majority of all herbivores will occasionally eat meat to get some extra protein into their diet. It’s actually a scale. You have pure carnivores on one side and pure herbivores on the other side and most animals falls near the middle. That’s why it’s recommended that if you have rabbits and they have babies, you should separate them so the rabbits don’t eat their babies. Another reason why animals would kill their own child is because baby animals make sounds to alert their parents that they need food or something else and if a threat is present, parent animals will kill the baby so that the baby doesn’t get the parent killed. The animal kingdom is absolutely brutal and most people live their whole lives unaware of this. Deer and creatures we consider “herbivores” actually eat baby birds that fall out of the nest. Similarly, carnivores will occasionally eat vegetables and fruit in order to get vitamins that they don’t normally get in their diet. Dogs are descendants of wolves and cats are descendants of wild cats but still both of them eat vegetables and grains in order to get a balanced diet. It’s actually seriously rare to find a pure carnivore or a pure herbivore. Majority of all animals are opportunistic and will eat whatever food is available.
I’m pretty sure spiders do this. Like I know some species where the mum bites off the head of the dad after she gets pregnant then she gives birth and dies and her babies hatch then either fly away in the wind or eat her dead corpse. Not all spiders do this but some do. I also know that a lot of animals including bunny rabbits will kill their own babies and eat them if food is scarce or if the babies are just being annoying and needy that day. You’ll find a lot of parricide or prolicide in the animal kingdom so technically he’s not being really really messed up but that the world is messed up enough that it happens anyways(?) but mainly the author is just straight up a psychopath cause even though I know the word to describe killing someone’s own parent or child, I would never in a million billion years think of adding it to a book. Just straight up craziness.