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CLIL > Natural Sciences

Kangaroos and koalas

tv icon Erna Walraven is the senior curator at Taronga Zoo, in Sydney. Among the native Australian fauna they keep there, maybe the two most well-known animals are the kangaroo and the koala. Both of them are marsupials, which means that they keep their babies in a pouch until they grow up and become independent. Erna explains the amazing reproductive system of these unique animals, how they are born and the dangers they have to face until they reach their mother's pouch.

 

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This is Taronga Zoo, my name is Erna Walraven, I'm the senior curator at Taronga Zoo. The scientific group name for kangaroos is macropods, and that means "big foot". So there's a big family of them and there are some... close to 50, I think 40 something species. So they're different, there's a grey kangaroo, and a red kangaroo, and a red neck wallaby, and many many different ones, a wallaroo, and they're all different, they're whole different species. They've got a fascinating reproductive system in that they have a pouch, so their offspring is born tiny tiny, it's like a tiny little embryo, and it makes its way from a part of the body called the cloaca, which is where all the external exits are from the body for wee, for poo, and for reproduction and for birth they all come together in one opening which is called the cloaca and the baby makes its way from the cloaca all the way to the pouch and attaches itself to a nipple there and it stays there, depending on the species, for months and months. The amazing thing is that kangaroos can have two babies, so whilst they have one that are just about... is just about coming out of the pouch, it starts to hop around but it still sticks its... er... head in the pouch for milk, it can activate its other ovary, where they've had a dormant little pouch young, that then develops and is born, and at one point a kangaroo will have a young at heel, as it's called, or at foot, so still sticking the head in the pouch and drinking milk, and it can have a tiny little baby on the other nipple, so they've got two nipples in the pouch mostly, and the interesting thing is, they make two different types of milk for different stages of development, for those... for those youngsters, so absolutely fascinating creatures. And they call that primi... primitive! I think it's such a good system of reproduction and they're... they're a wonderful group of animals and so interesting.

Koalas are known to sleep all day and that is true. They probably sleep some 22 hours per day. It is because they have a very fine energy balance. There isn't an awful lot of nutrition in eucaliptus leaves, and they also have a degree of toxicity in the eucaliptus leaves. So, it is important that they don't spend too much energy by jumping around and running around and being awake, because they haven't got the nutritional backup to do that. So their energy balance is fine, therefore they rest and sleep a lot. And so it's a privilege when you get to see a koala that's awake and active.
Koalas are marsupials too, they give birth to a tiny tiny little embryo for offspring, and like the kangaroos the little offspring needs to make its way all the way from the birth canal and then through the hairs of mum's tummy it makes to pull itself up and to get into the pouch, and attach itself to a nipple. Obviously things go wrong sometimes when that happens, it's a long journey for a tiny little animal. They're about that size, the size of your pinky nail really, and from the birth canal to the pouch they need to travel about that far, so that's a long way. Only their arms are developed at that stage. They're really really tiny, just like a jelly bean with arms, and the arms are strong because they need to pull themselves up. There they attach themselves to the pouch and they stay completely in the pouch for about five months, and from that time little bits of time the head will start to come out, and then obviously this one is a little bit bigger and it's fully emerged. It's probably just over a year old. They still ride on mum's back most of the time when she travels and right now she's still attached to mum all the time. But this little one is already starting to eat some eucaliptus leaves.

How long do koalas live normally?

Koalas live about 12 to 14 years. They are possible... they can possibly reproduce till about the age of 10. Most females once they're 9 years old that's probably their last offspring but males can be reproductively active until they're 10-11. Mostly the females find it harder to bring up the joey when they're advanced in age.

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