That’s a lot of vaginas: the highly adapted reproductive system of the female kangaroo

Kangaroos, they’re Australian icons. They’re on our 50c coins, our QANTAS jets and on the bodies of bogans everywhere, inked with an Australian made tattoo. But how well do you really know them? Do you, for example, know how many vaginas they have?

Well it’s three. Three vaginas. That’s how many passages to parenthood the female kangaroo has. And since we’re on the topic, these vaginas are followed by not one, but 2 uteri which in turn are followed by a pair of ovaries.

But even with all the gonads in the world, the female kangaroo can only produce a joey the size of a gummy bear. So what’s the deal? Why all the vaginas?

Time for a diagram!

Kangaroo reproductive system
No it’s not an alien: The unique reproductive system of the female kangaroo. There are two outer vaginas which sperm travels up and a third central vagina which the baby joey travels down – Source: Anna Gardiner

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.

But what are the benefits of this? Why would the kangaroo evolve this three-vagina-peanut-producing strategy? One hypothesis is that it helps them take advantage of times when there is plenty of food and water, an adaptation especially important in drought prone Australia.

Kangaroo
I think the sun was in their eyes: Mum and joey, hanging out – Source: Anna Gardiner

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.

It helps make the reproductive system of the female kangaroo, highly adaptive to the harsh Australian landscape. When times are good she can have her own continuous production line of little baby kangas and it’s largely thanks to her three vaginas.

Kangaroo 2
Kangaroo mob of three – Source: Anna Gardiner

So I hope I leave you now with a more intimate understanding of our fair dinkem aussie icon, the kangaroo. I do however, also apologise in advance if the word kangaroo is now forever associated with vagina in your mind.

Odd Organisms out xx

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