The Chive published a post that said,
Kangaroos have three vaginas—which means they can be perpetually pregnant.
Uhhh…what? Really? I usually take the “facts” that are posted on The Chive with a grain of salt. First of all, THREE VAGINAS? And secondly, the notion that those poor does (female kangaroos) could be pregnant ALL THE TIME…yikes!
A little research proved that yes, not only do kangaroos have three vaginal canals, but that this is the norm for marsupials. Koalas, wombats, and Tasmanian Devils all have this plumbing that seems very complicated in relation to ours.
According to Odd Organisms:
Strangely enough, not all three vaginas do the same job. Sperm travels up the outer two only, and expectant baby joeys travel down the central one. All vaginas however, are incredibly thin and narrow which means mechanically speaking, a baby larger then a peanut wouldn’t be able to fit through anyway.
Because baby joeys aren’t able to develop much inside the mother due to size allowances, her pregnancy lasts a breezy 33 days, and as soon as she gives birth she’s ready to mate again. After mating, she also has the magical power of embryonic diapause, where she’s able to delay the development of her next baby joey until the one currently suckling has left the pouch.
This means a kangaroo mother can be perpetually pregnant (gasp), the whole thing working like a factory production line. She can have one joey outside the pouch close by, one joey inside the pouch suckling and a third joey inside her waiting to develop further.
Is having two uteri something uniquely weird about kangaroos?
No. Having a single uterus is weird. Only anteaters, sloths, some bats, and higher primates (i.e. apes including humans) have a single uterus. In the apes, this seems to be a further development of the ‘bicornate’ uterus of monkeys, which developed from the more conventional pair of uteri found in most mammals.
In conclusion, The Chive was indeed correct, and I learned something new about kangaroos (and marsupials in general) today!