Are humans the only species that intentionally abort pregnancies?

 Are humans the only species that intentionally abort pregnancies?

Nope, although we are one of the few that has to intervene because we have evolved to hang on to pregnancy tooth and nail. The human fetus is surprisingly hardy: the womb is not a “nice, warm, safe” place, and it washes out anything that is not useful after a month (hence why we are one of the few species with menstruation). So the zygote has to hurry up and latch to the uterine wall (which is why we sometimes have out-of-womb pregnancies, like in a Fallopian tube), and then the mother’s body might try to reject this foreign body with antibodies and white cells. The embryo might be harmed by anything the mother consumes, so it makes certain smells unappealing and certain others (often in weird combinations) completely delectable so the mother will eat exactly what the embryo needs. On top of that, the embryo secretes “attachment hormones” such as oxytocine directly into the mother’s bloodstream, to ensure that she will put up with 9 months of ordeals.

It’s a delicate balance that might be thrown off by hormones or even violent movements.

Animals, on the other hand, have relatively “easy” contraception methods. Armadillos can “pause” their pregnancy if food becomes scarce. Some mammals (such as rats, mice and cats) can reabsorb the fetuses if there’s too much danger to raise them (excessive population, not enough food, too many predators around). Birds can push excess eggs out of the nest before they hatch.

Infanticide is more common, however; new-borns with something wrong (this is often a mystery to humans, who then care for the baby themselves) can be rejected or even outright killed by the mother. For instance, Tasmania Devils only have 4 teats, so the first 4 babies to make it to the pouch and latch on will grow, and the others (which can be up to 30) will be eaten by the mom to stimulate milk production. Some male animals, such as walruses, seals and lions will kill pups that are not theirs, to force the mother into heat again and mate with her so his babies are the only ones that survive. Sometimes, the “alpha” hyena and, in some situations, wolves, will kill any other females’ litters; this means that everyone will be busy making sure her cubs and her cubs alone survive.