Marsupial Reproductive System Marsupial's 3 Vaginas and 2 Pronged Penis

All female marsupials, such as a koalas, kangaroos etc., have three vaginas and two uteruses. Male marsupials, except the macropods such as kangaroos and wallabies, have a two-pronged penis.

Baby marsupials are not born in the mother's pouch. Instead, they are born through the mother's birth canal and crawl their way up her body to her pouch. Many die trying.

All marsupial females carry their underdeveloped young in a pouch or a depression on her abdomen equipped with nipples to supply milk. Male marsupials don't have a pouch or nipples.

Marsupials do not have separate openings for intestinal, urinary, and genital tracts. Instead, they have a single opening, called a cloaca, in which all these functions are served.

Related Article: What is a Marsupial?

Male Marsupial Reproductive Anatomy Look at the Koala's Two-Pronged Penis

Male marsupials, such as the koala, have a two-pronged penis (bifurcated penis). The end of the penis is split into two prongs (see photo). This means that each prong enters the corresponding left and right vaginas of the female. The shape of the end of the penis varies between the various marsupial species. (Note: Macropods such as the kangaroo and the marsupial mole, which are also marsupials don't have a two-pronged penis.)

Also, a marsupial's penis is located behind its scrotum. (Most animals have the penis located in front). When flaccid, the marsupial's penis is withdrawn and safely tucked away inside its cloaca.

Most male marsupials have a fur-covered non-pendulous scrotum, which means their scrotum (balls) are held close against their bodies. Macropods, like the kangaroo and wallaby, however, have pendulous scrotum. They dangle below the animal's body but are retracted when hopping or engaging in coitus. The Tasmanian tiger did one better; it had a special scrotum pouch in which it tucked away its scrotum and testicles for safekeeping.

Because sperm production is energy-intensive, marsupial males have tailored their sperm production to deal with Australia's harsh environment. They have adopted three strategies. Adult kangaroos, wallabies, and rat-kangaroos produce sperm continuously and are therefore always fertile. However, in periods of extreme stress, such as a drought when food is in short supply, their bodies shut down sperm production to conserve energy. Greater gliders only produce sperm during the mating season, and at other times sperm production is shut down. An extreme strategy is that of the antechinus, which makes sperm only once in its lifetime, synchronised with the female's oestrus period (fertility period). After copulating as many times as possible during this time, the male dies in a few days.

Female Marsupial - 3 Vaginas & 2 Uteruses Female Marsupial Reproductive Anatomy

The female marsupial has three vaginas and two uteruses (uteri). The two outermost vaginas are used for sperm transportation to the two uteruses above them. Babies are born through the middle vagina. By contrast, female placental mammals have only one uterus and one vagina. (See photo).

In some marsupials, such as the macropods (kangaroos, wallabies), this unique reproductive system results in a female being in a continuous state of pregnancy, with a fertilised egg in one uterus waiting to be released, a baby growing in the second uterus, one in her pouch and another hopping outside but coming to its mother for milk. Another unique feature of these animals is that during extreme drought and starvation, the female marsupial can practice birth control by putting the babies growing in her uteruses "on hold", stopping their future development until conditions improve. This is called embryonic diapause. Then, when the mother's pouch becomes free, the next baby will be born, and the fertilised egg will start developing into a new foetus.

Marsupial Pouch? Not All Marsupials Have a Pouch

Marsupials are mammals that give birth to embryonic babies that continue their growth attached to nipples on the mother’s lower belly. Many marsupials, such as the kangaroo and koala, have pouches in which their babies grow. Others, such as the antechinus and Tasmanian Devil, merely have a fold of skin to keep her litter in place. Some marsupials, such as the American short-tailed opossum, have only nipples onto which their young attach themselves.

Only female marsupials have a pouch or a depression in her abdomen in which she carries her offspring. A male marsupial does not have a pouch. A female marsupial isn't born with a pouch, but instead, her pouch develops as she begins to reach sexual maturity.

The female marsupial's pouch is located on the front of her body. It has an opening that can be drawn shut by powerful muscles when required. The marsupial's pouch is lined with muscles and ligaments expand to accommodate the growing joey inside.

The inside of the pouch is warm, nearly fur-less, with four teats that supply milk with different nutrient levels. Because kangaroo babies are born underdeveloped, her pouch acts as a second womb to permit her young to grow into viable offspring.

Marsupial Sex How Marsupial Mate

Various marsupials have different breeding cycles and durations. Kangaroos, for example, usually have one young per year from October to March. The koala breeding season is between September and March, and they have one offspring per year. Antechinuses breed only once in their lifetimes and then die.

Marsupial Egg

The marsupial egg descends from an ovary into a uterus, where it is fertilised. Once fertilised, the egg is encased in a fragile shell similar to that of birds and reptiles. This shell is just a few microns thick and disintegrates when the egg reaches the third gestation phase.

Marsupials only develop a very 'primitive' choriovitelline placenta where the egg, with its embryo inside, is attached to the mother's uterine wall for a very short period and doesn't develop into a chorioallantoic placenta like in placental mammals. (The only exception is in bandicoots). The gestation period for a marsupial is between 10.5 to 35 days depending on the type of species.

Marsupial Birth & Development How the Baby Joey Gets to the Pouch

Before the birth of marsupial young, the female cleans out her pouch by sticking her head into her pouch, licking the inside clean. It then takes up a "birthing position" and licks its birth canal opening to stimulate the birth.

The young marsupials, ranging in size from no larger than a grain of rice to about the size of a jelly-bean, soon emerges from the birth canal. It is born blind, hairless, with stumpy forelimb and hardly any trace of its hind legs. Even though it is still underdeveloped, the young newborn has an excellent sense of direction, knowing which way is up and down, and an acute sense of smell. Using its little forelimbs in a swimming motion, the young joey crawls laboriously to its mother's fur to the pouch. This journey takes about three minutes. The joey's journey is made entirely by itself. The mother does not assist in any way. Once inside its mother's pouch, the joey quickly attaches itself firmly to a nipple in the pouch.

Once it has attached itself to its mother's nipple, the young joey will stay hidden until it is ready to venture outside. Then it will start to tentatively pop its head out of its mother's pouch and observe the world around it. Finally, after having gained enough confidence, it will venture out of the pouch.

A baby marsupial is called a "joey".

Marsupial Milk

Marsupial babies are nourished with milk supplied by their mothers through nipples. Because their young are born relatively underdeveloped, these young animals lactate for a very long time compared to equivalent placental animals.