I have been fascinated by Australian fauna since our first trip to the remote yet huge continent island 7 years ago. Having a great colleague taking us to visit Healesville Sanctuary was an amazing way to spend a chilly Saturday. Started in the 1920s, this is a natural zoo set on a bushland environment, that has a long story of conservation being one of the two places that has successfully bred a platypus.
To get there, we took a train from Southern Cross station in Docklands and then were driven from there. If you plan to visit this area during your trip to Melbourne - highly advised as this can be combined with lunch at a lovely winery we'll talk about in a another post - maybe best is to rent a car.
Look carefully at the kangaroos legs, definitely not quite ours right?
The relationships among the three extant divisions of mammals: monotremes, marsupials, and placentals is quite interesting specially given that 2 out of these 3 divisions are nearly endemic to Australia. The detailed reason remains under discussion, but under the agreement that the ancestors of marsupials were living in different parts of Pangea millions of years ago, but eventually they became extinct in nearly all of them, except Australia.
Summarizing:
- Mononotremes: Echidnas and Platypus featured in the video below are only found in Australia, the only surviving members of the order Monotremata i.e. mammals that lay eggs. Echidnas evolved between 20 and 50 million years ago, descending from a platypus-like monotreme, which was acuatic even though they have adapted to life on land.
- Marsupials: Koalas and kangaroos you probably knew, but also wombats, wallabies, possums and tasmanian devils. All species endemic to Australia, except for the opossum which is also found in Central America. Their more distinctive feature is to carry the young inside a pouch and their common lack of knees on behalf of epipubic bones, which you can observe in kangaroos legs whose function is to stiffen the body during locomotion. Females give birth typically to a single joey, born while at the embryonic stage with relatively well-developed lips, forelimbs and shoulders, as well as functioning respiratory, digestive, and urinary systems. The joey crawls into its mother's pouch to continue the rest of its development.
- Placentals: Our common conception of mammal is actually only one of the three main groups - anything from elephants to whales through cats and humans.
Koalas
These cute animals are my absolute favourite and amazed since we visited Currumbin, 7 years ago. They live on Eucalyptus leaves, which are extremely low calorie. Typically steady as they sleep about 20h per day, they have huge heads but filled with liquid inside of which a really tiny brain is floating. They are asocial animals who spend just 15 minutes a day on social behaviours. Koala joeys are born a month old, but will stay in the pouch for 26 weeks before crawling out and tasting the eucalyptus. Hence, it was really cool to see them so active in a rainy and chilly day. They were jumping around, climbing and moving, something extremely rare.
Monotreme gang: Echidnas and Platypus
Mammals that lay eggs but nurse their babies with milk. Echidnas and Platypus featured in this video are the only surviving members of the order Monotremata.
While at first sight, echidnas may be confused with a plain hedgehog, they are not. If you look carefully, you will note a thin beak-like mouth - which they use to feed in ants, on the fashion of the platypus. This is because echidnas evolved between 20 and 50 million years ago, descending from a platypus-like monotreme which was acuatic, even though they have adapted to life on land. Their reproduction is very interesting. 22 days after mating, the female lays a single and deposits it directly into her pouch. 10 days after, baby echidna called puggle, opens the leather shell with a reptile-like egg tooth. The baby is something between a larva and a foetus, sucks milk from the pores of the two milk patches (monotremes have no nipples) and remains in the pouch for 2 months more, when it starts to develop spines. Mamma echidna digs a nursery burrow, deposits the young and returns every five days to suckle it until it is weaned at seven months. Puggles will stay within their mother's den for up to a year before leaving. If you look at their back feet, you can see the toes point "backwards" in a strange way. This helps them bury themselves quickly when they feel endangered, so the spines are the only thing showing. They sometimes curl into a ball also using their spines as shield.
Where to start with the platypus, an animal so weird that the first European visitors assumed to be a hoax.
They look cute, but watch out with the males! One of the few species of venomous mammals, they have a spur on the hind foot that delivers a venom capable of causing severe pain to humans.
Platypus are the only mammals (apart from another species of dolphin) known to have a sense of electroreception, to locate their prey in part by detecting electric fields generated by muscular contractions. The platypus can determine the direction of an electric source by comparing differences in signal strength across the sheet of electroreceptors. This explains the side-to-side motion of the animal's head while hunting - seen also in the Hammerhead shark. When they dive, their eyes, ears and nose remain closed. The electroreceptors in the bill detect tiny electric currents, making it possible to distinguish between animate and inanimate object.
Their reproduction is also rather convoluted. First the females lay 1 to 3 eggs, which are developed in-utero for 28 days and incubated externally for 10. The incubation period has 3 phases, during the first one the embryo lives on the yolk sac, the digits develop during the second one and the egg tooth appears in the third to facilitate the hatching. Just like with echidnas, the platypus are very vulnerable after hatching the egg and will remain in the pouch for 3-4 months. The tooth drops during this period, leaving the plates it uses to grind food.
The one featured in the video is a female, which is not poisonous and therefore very safe for the caretaker who was clearly her best friend.
Healesville Sanctuary [WEB]
Everyday: 9-17
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