Koala Reproduction

 

Koala mother
carrying a joey
(baby) on her
back

  photo of a koala mother carrying a joey (baby) on her back
       

Koalas have a comparatively short gestation period of 34-36 days.  They usually have only one baby (known as a joey) per year.  Their newborn are 3/4 inch (1.9 cm.) long and less than 1 gram in weight.  They appear to be still at an immature fetal stage.  They are pink, hairless, blind, and deaf (they have no ears at this time).  However, they have a good sense of smell, a sense of direction, and strong hands which they use to crawl unaided from the birth canal to their mother's abdominal downward facing pouch.  There are two nipples inside the pouch.  The joey usually remains more or less anchored to a nipple for half of a year.  Milk is the only food during this period.  The nipple swells in the joey's mouth, which helps it remain anchored there.  The mother also contracts the opening of her pouch to prevent her baby from falling out.

By 6 months, joeys are fist size and look like an adult in their proportions.  They now have fur as well as functioning eyes and ears.  They periodically leave the pouch beginning at this time to explore their immediate surroundings but return to hide and sleep.  They also transition to being carried on their mother's back.  Their teeth are starting to erupt, which allows them to gradually switch to a diet of eucalyptus leaves.  This begins by the joey eating the mother's "pap" which comes from her cecum (a small pouch between the small intestine and the colon).  This soft, runny "pap" is a specialized form of protein rich feces containing bacteria that allow koalas to digest what would otherwise be toxic eucalyptus leaves.  The bacteria become permanent residents in the joey's digestive system.  When weaning is complete by around 12 months, the mother leaves her joey to fend for itself.

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Copyright 2011-2012 by Dennis O'Neil. All rights reserved.
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