Wildlife down under!

Australia is an incredible place where animals of all shapes and sizes can thrive. It is the only continent that still has all three major groups of mammals: marsupials, monotremes and placentals. The three types of mammals each have their unique way. Monotremes are egg-laying mammals, there are only five species in the world and two of these live in Australia [1], examples of these include Platypus and the Echidna (shown below). Placentals are your “normal” mammals, they birth live young that are nourished in the womb by the placenta and out of the womb by the mother’s teats [2]. Marsupials give birth to a tiny, less developed foetus with only a mouth, digestive system and small arms that they use to climb into a pouch or skin flaps where they latch onto their mother’s teat for weeks while they develop [2].

Over half of Australia’s mammal species are marsupials and they have no hoofed mammals, monkeys, cats, dogs or bears are native to Australia [2], even the dingo only arrived from Southeast Asia 4000 years ago [3]. 84% of land-dwelling mammals in Australia are endemic, meaning they aren’t found naturally anywhere else in the world except for Australia, New Guinea and neighbouring islands [2]. What’s interesting about Australian placentals is that all of them must have flown or swum there [4], these include bats, seals, sea lions, dugongs, whales and dolphins [3]. The only placentals that couldn’t have flown to swum to Australia are the rodents (which arrived only 5 million years ago) and other mammals that were brought by humans (who arrived 60,000 years ago) [4]. This potentially suggests that the only mammals that originate entirely from Australia are marsupials. But ancient marsupials are actually from North America, but they didn’t last very long because a lot of the niches were already filled by placental mammals [5]. So they went to South America and filled the same niches that were full up North and they thrived and diversified [5]. They then worked their way round to Australia via the Antarctic (as these three were connected back then). In Australia they thrived even more than they had in South America, it’s unclear why but some suggest it’s because their young had a better chance of surviving in their pouch than the placental mammals’ babies who were either carried around on their mother’s backs or in hiding while their mother used up her resources on her young [5]. Also, as previously stated, it’s very unlikely that there were many (if any) placental mammals in Australia for the marsupials to compete with meaning they could exploit every niche available and thrive [5]. However, a fossil tooth from a placental mammal was discovered in Australia 55 million years ago meaning there was the presence of at least some placental mammals, but not enough to outcompete them because they are still found there today [5]. An easy way to see where the marsupials are suited best, just look at the figures; in North America, there are only one species of marsupial- the Virginia opossum-, in South America there are 120 marsupial species and in Australia, there are 250 marsupial species [5].

My favourite marsupials

A Kangaroo with her baby

A Wombat

However, the introduction of one of my least favourite placental mammals to Australia 45,000-50,000 years ago (humans) has caused one-quarter of all native Australian mammals to disappear [4]. Some of the most incredible marsupials such as the giant rat kangaroo, the thunderbirds and the giant goannas are all gone, these guys lasted years of natural change in Australia but couldn’t survive humans [4]. Some species did survive the humans, such as the red Kangaroo, dingoes, emus and wombats [4], but we want them to stay that way!

Australia currently has the worst mammal extinction rate in the world with loss of habitat from tree clearing and the pressure of invasive species and diseases, on top of that, last summer’s bushfires caused the death of 1.25 billion animals [6]. If you click the link here you can find out how to help protect these amazing species.

Animals have thrived and lived well without us before, and they will do after us but we have to do our part to help them now. Our presence has caused the loss of so many incredible species and we need to do more to protect the ones that we have left.