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You are here: Home / Animals / Why do Kangaroos and Marsupials have Short Gestation Periods and How Big is a Baby Kangaroo when it’s Born?

Why do Kangaroos and Marsupials have Short Gestation Periods and How Big is a Baby Kangaroo when it’s Born?

April 13, 2020 by Karen Hill

A baby kangaroo is a little larger than a lima bean, but smaller than a full-size peanut when it’s born.

And it’s not very cute, unless you’re the kind of person who finds slimy pink animal babies irresistibly adorable.

baby kangaroo and dog

Kangaroos are marsupials, as are most of the mammals that are native to Australia. Besides looking pretty weird, how are marsupials different from the others?

Most mammals are placental, meaning the fetus develops in the womb and is fed directly from its mother’s bloodstream by a placenta. Hundreds of millions of years ago, though, marsupials went down a different evolutionary path.

Instead of giving birth to well-developed young after a long gestation period, marsupials give birth to tiny, hairless, helpless, blind, nearly larval young after a much shorter gestation.

Looking like undeveloped fetuses, the young are instinctively capable of only two things after being born: crawling up the fur of their mom to the safety of her marsupium or pouch, and finding a nipple there to suck upon.

In the case of a kangaroo, gestation is only thirty to forty days, and then the little joey attaches itself to the mother’s teat for six or seven months. After that time, the baby finally grows into a miniature version of its parents. It begins leaving Mom’s pouch for short hops before returning for food, rest, and safety.

Other marsupials have similar developmental patterns involving short gestation, a long time in the pocket, then gradual integration into the world.

These New Parents Are Really Jumpy.

Related Facts

  • How many Marsupials Mammal Species Live in America and How did they get here From Australia?
  • Why Does the Kangaroo Have a Pouch?
  • Do all Kangaroos and Marsupials have Pouches for Babies to Live and Hide until they are Old Enough to Leave?
  • How do Marsupials Mate and Reproduce with Forked Penises and Two Vaginas to Separate Uteruses?
  • How did the Kangaroo Rat get its Name, Where does it Live, and is it a Native of Australia?
  • Which Animals Besides The Platypus And Kangaroo Live In Australia And Nowhere Else In The World?

Filed Under: Animals

About Karen Hill

Karen Hill is a freelance writer, editor, and columnist. Born in New York, her work has appeared in the Examiner, Yahoo News, Buzzfeed, among others.

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Next Post: Why do Kangaroos Hop Instead of Walking or Running and How Fast can they Hop? »

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