A few posts back (Morality vs. Liberty), I stated that "abortion is different - a species should not kill it's own". It's funny that looking at that statement by itself makes me look pro-life - which I am. But I'm also pro-choice. Some things are not so cut and dry.
So anyway, I made that statement which I really didn't give much thought to - but today I started thinking about certain cases in the animal kingdom where species DO kill their own, and I'm not just talking about adults killing adults (for instance, where the female praying mantis consumes the male while copulating with him, or where the dominant hippo kills a younger male who challenges his right to a territory). No, I'm talking about adult animals killing young, powerless members of their own species. From a human perspective, many pro-lifers equate abortion of an unborn child to the killing of a young child, so the following list of animals that commit infanticide may come as a shock to them. In other words, it is a more common practice than you might think.
--> Many rodents show infanticide, including rats, ground squirrels, lemmings, hamsters, mice, voles, muskrats, gerbils, prairie dogs and marmots.
--> Rats and mice: When populations of mice and rats rise rapidly, the hungry and stressed survivors may kill and eat young. Ratbehavior.org goes into detail about infanticide in Norway rats. This is usually directed towards newborn rats. A mother pet rat may eat her own offspring. Mothers tend to kill deformed or wounded infants, which may allow her to allocate resources to the healthy pups, which are more likely to survive. Mothers may also kill litters when they are stressed, perhaps because she perceives the environment as too hostile for pup survival, or if she cannot to rear the litter successfully. She recuperates some her energetic investment by consuming the young. Malnourished mothers, and mothers who have an abnormal birth experience, may also become infanticidal. An unrelated adult male rat may kill young to bring the mother back into estrus sooner, so he can sire a litter of his own. Maternal aggression after the birth of a litter may reduce infanticide. Unrelated females may kill young rats to gain food and take over the nest.
--> Eastern grey squirrels: This website states that some males kill the young so that the females re-enter estrus. The Tennessee Animal Biogeographic System website states that captive, stressed females may kill their young.
--> Belding's ground squirrels: When Belding's ground squirrels fail to attend their territories, unrelated females or one-year-old males may arrive and kill pups. Yearling males usually eat the carcasses, so their infanticide may be motivated by hunger. When a predators kill a female's young, the female often emigrates to a new, safer site and kills the young there before she can settle. By removing juvenile females who may remain in the preferred area, infanticidal females reduce further competition for a nest site. Mothers with close relatives as neighbors lose fewer young to infanticides than females without neighboring kin. This is because groups of females detect marauders more quickly and expel them more rapidly than individuals acting alone, and because a female's relatives defend her young when she is away from home.
--> African hunting dogs: I remember a documentary about hunting dogs, where a dominant female tried to kill all the pups of another female. The documentary crew retrieved the last pup and named it Solo. Eventually Solo was reintroduced to the pack.
--> Lions: The University of Michigan zoology website and others state that when new adult lions take over a pride, they often kill the young and thus eliminate the chance of any rivalry against offspring he later fathers. This often causes the females to enter estrus after 2-3 weeks, much more quickly than if a female came into estrus after her cubs have become independent. The males mate with the female and help protect the females and their offspring, rather than protecting the young sired by the previous males. Lions may occasionally eat the cubs. Successful males that takeover a pride have about 2 years before another younger, stronger coalition will replace them. This is the same time a male would have to wait before nursing females entered estrus after their cubs became independent – by this time, a new male would probably take off the pride and the ‘patient' males would not longer be able to mate. Killing the cubs means that the males have a chance of leaving offspring, although females vigorously defend their cubs during a takeover.
--> Butterflies: The caterpillars of Monarch and Queen butterflies often eat the eggs of the species.
--> Bottle-nosed dolphins: The Polperro Dolphin Swims website states that adult bottle-nosed dolphins kill the young of their own species. This may be because competing adult males may be killing the offspring of their rivals so that the dead dolphin's mother will be receptive to mating. Researchers believe that females remain sexually inactive for years when raising their young, but become active again soon after their loss. This murderous behavior is not an uncommon feature within the animal kingdom. Large terrestrial carnivores, such as bears and lions, have been known to perform similar acts of infanticide to help start up their own dynasties to compete with their rivals.
--> Baboons: Ryne A. Palombit, of Rutgers University, studies male infanticide in chacma baboons, where a social relationship between males and lactating females leads to a decrease in infanticide. Similar relationships occur in olive baboons, where male infanticide is much less common.
--> Langurs and other primates: The males of several primate species, including the common langur, practice infanticide. Bands of male langurs will attack a mixed troop, driving off the males and killing the offspring before mating with the females. Baboons also kill their young and occasionally even eat them. Dominant male gorillas and chimpanzees may kill the young of their species, but infanticide does not seem to occur in bonobos.
--> Gulls and other birds: This strange website states that many species of gull that nest in large colonies eat eggs and young. This may be a response to crowding, but male gulls, which lack young of their own, are more likely to eat the eggs and young of their own species. Some parent birds may eat the young when populations become dense, or food scarce. Crows may eat eggs and chicks of rivals to improve their own chance of successful breeding.
--> Kangaroos: Kangaroos can have three young at different stages of development. One inside the body, one in the pouch and one that lives outside the pouch for much of the time, but still suckles from the mother. In severe conditions, the mother may not have enough energy to feed the older young, so this is left to its own devices. If conditions deteriorate, the mother will remove the pouch young. This means that the embryo in the body develops and soon occupies the vacant pouch. Whether this course of action counts as infanticide is debatable, but if the mother died, so would the young.
Naturalists have identified dozens of species that kill their young, including the animals listed above, as well as hippos, bears, wolves, hyenas, herring gulls and more than 15 types of primates other than man. Humans are not alone. Like these animals, we are not non-maleficent robots that live for the group and kill only to eat. Instead, we are programmed for selfish, even murderous acts when survival and propagation are threatened. Luckily for all of us, survival and propagation are not as difficult to achieve as humans. Maybe this is why some view abortion as such a heinous crime - it is usually done for only selfish reasons. Then again, I think we can afford to be, given that humans are one of the most successful species this planet has ever seen.
