And because of the dedication of zoo curator Kylie Elliott and general manager Matt Radnidge,  it looks set to have a  happy ending.

The young koalas have been on a delicate journey for the last three months, defying the odds to survive with the help of much tender loving care.

International interest started in June when the story of a young joey named Imogen and her mother, Kelly, went viral on social media when a video of Imogen’s first appearance from her mother’s pouch was captured by zoo staff and posted online.

Soon after, however, the mother of another younger koala named Harry died unexpectedly.

The tiny, orphaned joey was vulnerable and a tough decision needed to be made.

Harry had not yet emerged from his  mother’s pouch and weighed only 250 grams.

Imogen was about 30 weeks at the time, weighed about 500 grams and had emerged from her mother’s pouch.

Ms Elliott and Mr Radnidge consulted industry specialists about hand-rearing Imogen and attempting to  cross surrogate Harry into Kelly’s pouch. 

Koala surrogacy is thought to have only happened a handful of times so the  mission was watched with great interest by the zoological industry.

All went well with Kelly  taking over the role of nurturing mother and adopting Harry as her  own.

For Ms Elliott and Mr Radnidge,  hand-rearing Imogen involved taking her everywhere as well as many sleepless nights.

‘‘Hand-raising Imogen has been the most challenging and rewarding thing we have ever achieved,’’ Ms Elliott said.

‘‘It hasn’t been an easy journey raising a joey with nocturnal habits and sharp claws. I definitely have a new respect for koala mothers.’’

Thanks to their care and dedication this story looks set to have a  happy ending.

Harry  now weighs in at nearly 900 grams and has started exploring the  wider  world.

And as she approaches her first birthday, Imogen has grown to 1800 grams and is spending more time climbing around her branches and slowly learning how to become  independent.