Infanticide in Nature: Why Animals Hate Their Babies

welcome to the lovely study of Zoological infanticide which explores why animals kill the young of their own species from fish Birds microscopic organisms and lots and lots of mammals infanticide is a horrifyingly common theme across the animal kingdom and unsurprisingly it's a relatively under research a guy who would know much more about this than I would once said that infanticide has not received much study because it's a repulsive subject many people regard it as reprehensible to even think

about it but I've been thinking about it and not because I'm some child murdering psycho but because studying it means exploring the limits of how far an animal will go to raise its evolutionary Fitness in the right circumstances it might also give insight about underlying reasons for similar human behaviors like child abuse so I'm gonna talk about it in this video uh if you don't want to hear about it or don't want to think about it that's fine I understand feel free to click off but if you're

still here let's talk baby killing infanticide is a a common enough behavior for it to be considered non-random which in the case of biological traits usually means it's the result of an adaptation so it almost definitely has some evolved purpose that can lead to reproductive benefits or Fitness in the right situations for some it's as simple as cannibalizing their young for food male salmon will protect their clutch of eggs until hundreds of them hatch in which they chase after them as if they

're small prey mantids have no problem eating their young which isn't too strange considering they eat their mates too but even rats and monkeys have shown this Behavior other times it's not for the food itself but to reduce competition for food we see this in prairie dogs don't be fooled these cute faces belong to one of the most ruthless baby killers on the planet with still pet though but yeah these guys are insanely infanticidal and even kill the young of close relatives for what we think is

so that they can have more food to provide for their own children and it's easier to get close to the children of your own relatives making them easier targets but it gets a lot more complex than food and that's because in a lot of species it has to do with sex sex is a really complicated thing in the animal kingdom so generally animals act to produce as many offspring as possible and what you often get in mammals are males killing children that aren't their own in order to mate with their moth

er and generate new Offspring the incredibly messed up rationale being that if the mother is taking care of the other kids they're not going to want to raise theirs so if they get rid of those other kids they effectively reset the fitness of the female incentivizing them to reproduce with the offending male it's really messed up when you think about it but it does work in a lot of animals we see females in a bunch of species induced into estrus or heat as a response to their babies dying it's cr

azy but yeah so in Lions males will kill young cubs so that they can mate with their mothers about 25 percent of lion cubs that die in their first year are victims to infanticide we think that the reason these numbers are so high is because male lion have really short reproductive windows and female lions only reproduce once every two years in the wild meaning that the selective pressure to have your own offspring is very high thus encouraging harsher methods in order to make that happen in Hanu

man langers which are monkeys found in India social groups consist of a dominance hierarchy where one dominant male has control over mating with all the females if you're interested in why dominance hierarchies occur I made a video about this that you should check out later but what it means is that all the other males are subordinates in order to reproduce they might have to take over the dominant role this usually leads to a very aggressive battle and in the case where the original dominant is

overthrown the new dominant will kill the infants of the previous male most males being subordinate and thus unable to mate is another example of a strong selection pressure leading to these harsher Solutions this is basically the pattern that we see in infanticide is males having high selective pressure to reproduce but while we see that the vast majority of infanticide is committed by males in some species is we do see it done by the females this is seen in a lot of species where males are cr

ucial in raising the young and if males are a limited resource females will kill other females kids in order to acquire them so in waddled dracanas these beautiful South African birds the males brewed and helped the eggs hatch while the female defends the territory an experiment saw that removing the females of a nest caused other females to enter and kill the children where the male then fertilized the offending female and ended up raising their young we find the exact same thing in water bugs

where males will care for masses of eggs with their bodies same thing happens female comes in kills all the eggs the male ends up copulating with the female and starts caring for her eggs so this is a common pattern of killing other Offspring in order to create your own in both males and females depending on the particular pressures that the corresponding Sexes both face but what this doesn't explain is filial infanticide a very special type of infanticide that probably means what you're thinkin

g the killing of one's own children now all of us a sudden the explanations for evolutionary Fitness don't seem to make any sense because it can't be beneficial to kill your own progeny at least not for Reproductive Fitness there are some cases where it kind of makes sense like the bass eating their own offspring for food the thing is is that there are times where this doesn't make sense to us pigs are commonly known to be very aggressive to their newly born Offspring sometimes killing a lot of

them it's called savaging and it's common enough that places that raise pigs will often separate their mother from their newborn until the behavior won't happen anymore but we also see this in rabbits and hamsters and burying beetles a lot of animals really want to kill their own babies and we don't fully understand why but it's clear that there are multiple reasons why species commit infanticide as well as various types of it but do you know which group of animals does it the most well that'd b

e the order that we belong to good old primates we've talked about the Hanuman langers but a lot of other monkeys do this too and chimps are also very notable and ruthless when it comes to infanticide the other ruthless with a lot of things but if our closest relatives do it and our extended family tree does it why don't we why don't humans kill their young well the thing about that is we have a long long historical record of infanticide it's been used to control population size in response to c

hildren born of unwanted pregnancies or physical deformities it was also seen in a lot of old cultures for sacrificial rituals we've also seen humans display in fantaside to female children when they wanted a male the most common practice of infanticide even today which by the way this sex specific infanticide is unique to us good old humans expanding the scope of behaviors in all ways especially the bad ones so why are you and I so horrified by the idea of infanticide right like from my underst

anding it's pretty socially and ethically unacceptable to kill kids well that's because so far I've only talked about the situations where infanticide is beneficial but it isn't always the case that the benefits outweigh the cost because yeah there's a really big cost not everyone is happy after infanticide as you might imagine mothers of their young aren't the biggest fan of being on the receiving end of their children being killed believe it or not and remember how I mentioned that male infant

icide can actually induce estrus in certain female species well in some of them including humans females can actually enter a false estrus after infanticide we think it's to trick the male into thinking that he succeeded in reproduction effectively ruining the fitness prospect that he got from the advanticide in fact several species show countermeasures in response to infanticide punishing it as a viable Fitness strategy so I mentioned false estrus you know if you think your girl's faking it may

be make sure you don't kill their child there's also the Bruce effect in which a female will terminate a pregnancy internally also ruining the benefit of the male committing infanticide but one of the most efficient countermeasures is paternal uncertainty by mating with multiple males individual males can never be sure if a kid is theirs causing them to not kill any Offspring in risk that it is so a lot of animals are polygenous and paternal uncertainty actually plays a massive detective role fo

r females of these species but yeah Mori would be these animals worst nightmare in Social species infanticide is an especially more problematic Behavior to allow because if it's just left on the table then this doesn't bode well for anyone having children like I'd be pretty scared if I knew that people could go around harming my child and not be punished so we do punish these behaviors through social discouraging or sometimes just to forming coalitions to group up on the perpetrator exiling them

or killing them this plays in with Prestige where being kind is an attractive trait both sexually and socially infanticide would almost definitely ruin your reputation thus lowering your reproductive potential significantly so there are plenty of reasons to be against infanticide evolutionarily which explains why we probably aren't the biggest fans of the idea at least not at this point in history we've evolved a social structure that really doesn't allow for anyone to get away with such terrib

le things anymore but what about child abuse humans might not be able to outright commit infanticide but a lot of abuse of young children physically mentally or emotionally is still done and gotten away with a lot more than we realize could it be that the reasons behind infanticide in nature are the same ones that motivate child abuse well we don't actually know at all some scientists suspect that it does play A Part since we see animals having a much higher chance of killing young that aren't t

heir own and in human child abuse we see the well-documented Cinderella effect where step parents are more than 10 times likely to harm their child than biological ones I'm not trying to say that because these behaviors make sense naturally that they're in any way okay we are much more complex and better than how we evolved and we have a responsibility above that at this point but keeping it in mind might help us circumvent it on a large scale these mechanisms might not affect you but we don't k

now if that's the case for people of all different kinds humans and other animals are incredibly complex so complex that they sometimes kill their own babies but that's just a testament to how complicated animal behavior is it's not a support of that behavior but anyways yeah um I'm not sure how a video like this will go down but I hope you enjoyed it um and if you don't support infanticide you should subscribe I have a small anti-baby killing community that would love to have you but yeah take

care bye