2 - Is there abortion among other animals?

This is Number Two of who knows how many posts regarding what defines as as humans. Go here for the introductory post and previous one.

[NOTE: Heffalumps are VERY unwelcome. I do NOT wish to see any judgemental comments. Express your surprise, your glee, your disgust but not from a moral standpoint please. I am neither advocating nor berating abortion and its ramifications, I am simply presenting facts from animal societies and the kind of pregnancy control mechanisms they use. I know the regulars have the intelligence to see what this post is about; if you don’t, exit now or keep mum. Otherwise you'll annoy the hell out of me and I'll delete you bfr you can say "troll". Or I’ll just tell Danny and he’ll crash your computer. HA!]

Abortion: the voluntary termination of pregnancy

We agree that the purpose of an abortion is to end a pregnancy for WHATEVER reason, right? These are some mechanisms that animals use to control pregnancies and in some cases stop them. I’m including infanticide not because it relates to abortion per se but because abortion is in a broad sense a means of population control - i.e. you are effectivelly preventing natality - and so is infanticide, both having as a consequence the absence of offspring. I'm allowed to do this sort of thing bcs this is my blog you see.


QUICK OVERVIEW:

Monotremes - Egg-laying mammals (platypus and echidna). Reduced placenta. They have mammary glands but lack nipples. Cloaca (common vent for faeces and urine)
Marsupials - also have a cloaca but give birth to live young (vivipary). Reduced, inefficient placenta. Very short gestation period, give birth to poorly developed young.
Placentals - us and most mammals; viviparous, highly developed placenta that allows for exchanges between maternal and fetal circulatory systems. Longer gestation period.


USUAL SEQUENCE:

copulation -> ovulation-> fertilization -> pregnancy -> birth


1 - DELAYED FERTILISATION (DF)

copulation -> females store sperm -> ovulation -> fertilization

Seen in hibernating bats. Copulation occurs prior to hibernation, and sperm (spermatozoon, male gamete) is retained within the female throughout the hibernation period. Ovulation and fertilization occur when the ovum (female gamete) is released from the ovary after the bats arouse in the spring. DF is an adaptation to winter dormancy (males require some time post-hibernation before they produce sperm again) and is related to food availability and other weather-related factors.

Also found in other insect-eating bats, many insects, Gould's goanna (reptile from AU), mink (females store sperm from several males so one litter has more than one father).


2 - DELAYED IMPLANTATION (DI)

copulation -> ovulation -> fertilization-> early development -> dormancy -> implants and finishes development

The fertilised egg (ovum + spermatozoon) remains dormant in the uterus for a while before implantation on the uterine wall. This allows females to give birth around the same time each year when weather conditions (including food availability etc) are optimal. It allows for mating at the ideal time (female and male in their best physical condition) and bearing the young at the ideal time (friendly temperature, food availability). The intervening period is longer than the actual pregnancy.

Found in the bear family (including pandas), Mustelids (European badger, river and sea otters, wolverines, weasels), many bats, kangaroos and wallabies, insectivorans, armadillos, Mustelids, all Pinnipeds (fur and true seals, sea lions, walruses) and two species of roe deer.

The European roe deer is the only artiodactyl (even-toed hoofed mammal) to exhibit DI. After the egg is released from the ovary and fertilised by the sperm it travels to the womb where it remains floating for five months, during which the cells of the embryo divide and multiply slowly. Unlike other species with DI, the unimplanted embryo controls its own growth.


3 - DELAYED DEVELOPMENT

copulation -> fertilization -> implantation -> dormancy -> resumption of development

The fertilised egg implants after fertilization but the development is slow.

In bats of the G. Miniopterus ovulation, copulation and early embryonic development occur normally immediately before hibernation, but the embryo experiences developmental arrest before uterine attachment.


4 - EMBRYONIC DIAPAUSE

This variant is basically a form of delayed implantation found in marsupials. Development of the embryo is delayed as long as there is another infant suckling in the mother's pouch. When the infant leaves the pouch (or if it dies before doing so), the embryo that is in diapause starts to develop and is born soon after. This type of reproductive strategy is advantageous because it allows females to reproduce almost continuously and allows for almost immediate replacement of lost young. (This one is giving me a bit of grief bcs I read an article to the effect that the kangaroo milk from one single female is biochemically different in different teats so as to allow both the already jumping-around Roo and the still-embryonic and very much teat-attached Joey to have the exact milk composition they need. So I'll check further and will update bcs they can't very well have it both ways.)

AH!!! FOUND IT!!! I'm a bloody good detective is what I am!

"Species which have this unusual ability normally mate again soon after the female gives birth. The tiny newly born kangaroo (less than 25 mm long) moves unaided into its mother's pouch and attaches itself to one of four teats. During the early stages of pouch life the young is permanently attached to the teat, but as it matures and begins to grow hair it also develops the ability to release and reattach itself to the teat. In the late stages of pouch life, once it has a thin covering of fur, the young one begins to explore the outside world for increasing lengths of time until eventually it is old enough to be excluded permanently from the pouch. Complete weaning may take a number of months more after the young has permanently left the pouch. If the mother gives birth during this time, the newborn young will attach itself to a different teat to that being used by the older young. It is remarkable that when this happens the mother produces two different kinds of milk for the two different-aged young." I KNEW IT, I KNEW IT!

5 - SPONTANEOUS ABORTION

copulation -> fertilization -> abortion of embryos prior to normal end of gestation

The Bruce effect: when female mice encounter a strange male or his scent and the male who fertilized her is no longer around she aborts or reabsorbs her litter. By aborting her developing litter she’ll be able to mate with him and produce young that will live, rather than waste resources with a litter he will kill (because he didn’t sire them)


INFANTICIDE BY MALES

(I’ve chosen lions as an example because they are extensively documented but they are by no means the only ones)

“When a new male coalition takes over a pride they are often confronted by the cubs of the males they defeated. Males have no time to spare for protecting the offspring of their predecessors because their own time with a pride is limited. Females will not mate again until their cubs are at least 18 months of age; therefore, males kill all the young cubs in their new pride in order to bring the females back to reproductive readiness. Older cubs and sub-adults stand a chance, however, because they can often escape from infanticidal males. These cubs are evicted and must fend for themselves although occasionally their mothers will leave with them and remain apart from the pride until the cubs reach independence.

Female lions are also infanticidal and will kill the young cubs of rival prides; however, they never kill the cubs of other females within their own pride. This differentiates lions from predators such as wild dogs where dominant females prevent their companions from breeding. Females will often fight back when new males attempt to come and kill their cubs. In fact, defending cubs against infanticidal acts by outside males is one of the primary reasons why female lions live in groups. As the following video shows, there is strength in numbers, and groups of females can often defeat infanticidal males and successfully protect their cubs."


Go here for lionesses’ defence against infanticide (Have I mentioned lionesses kick ass? Never mind the tiny infanticide detail.) Go here for primate infanticide

Infanticide seems to be mostly done by males in primates. J. Goodall documented a female chimp, Passion, who, with her daughter Pom, killed and ate several babies in the group. Unlike what happens with males, these killings seemed to be only for the meat. I remember reading abt this duo in books and articles and this behaviour seems to be pathological. Although chimps love meat and will kill for it, their young seem to be safe for the most part. But there's more to chimps than meets the eye, I'll tell you abt it as I move along the list.

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So yes, abortion exists in the animal kingdom as well. And even though it’s not the same thing at all, embryos will sometimes not be allowed to implant/further develop under extreme adverse conditions (for a human equivalent let’s take the pill, an extremely adverse condition because, even though it doesn’t always prevent ovulation, it will almost always prevent implantation of the fertilised egg) (Again, I get away with these comparisons bcs it’s my blog and I just want to have a bit of fun and bring to you some of the wonders of Ethology, Bio-Anthropology and Biology). I just marvel at all these mechanisms and am, as always, in awe of animals and their astonishingly different evolutionary modes (evolution in a Darwinian sense means adaptation and not progress as most people seem to think). (Are you having fun reading all this? Is it too much? Should I make it shorter? Have you had enough?)

Thank you Ron (click on the link, it's fast and v funny!) for reminding me of something: "Strier found that, at different times, muriqui monkeys (Brachyteles arachnoides) of Brazil go out of their way to eat the leaves of Apuleia leiocarpa and Platypodium elegans, and the fruit of Enterlobium contortisiliquim (monkey's ear). The first two plants contain isoflavanoids, which are compounds similar to estrogen. Ingesting the leaves may increase estrogen levels in the body, thereby decreasing fertility. Alternatively, eating monkey's ear may increase the monkey's chances of becoming pregnant because the plant contains a precursor to progesterone (the "pregnancy hormone") called stigmasterol."

Read Wild Health, by Cindy Engels, for more on how animals self-medicate (includes getting drunk and hangover medicine). I promise you it's an absolutely worthy buy.