Close your eyes and think of the first few things that pop into your head when you think about Australia. Chances are, one of those things is an image of the kangaroo. They’re ubiquitous in Australia, and you can’t find them anywhere else outside of zoos, but why?
The Kangaroo in Australia
Kangaroos are marsupials, and they specifically belong to the macropod family. It’s easy to see why – the word macropod means “big foot.”
Marsupials are a type of mammal. These animals have tiny babies that finish their development in a pouch that contains mammary glands for the young to nurse. Kangaroos have a forward-facing pouch for their young, known as joeys.
Kangaroos come in several different forms. Some of these species include:
- The red kangaroo
- The eastern gray kangaroo
- The western gray kangaroo
Other related species include wallabies, tree kangaroos, and quokkas.
A Kangaroo’s Natural Habitat
So, we now know what a kangaroo is, but did you know they only live in Australia and Papua New Guinea? Unless in a zoo, you will not find it anywhere else.
Within Australia, kangaroos live in many different habitats, so there’s no one place you’ll find them. Each species has a different place they prefer to live.
- Tree-kangaroos prefer to live in trees within rainforest-type environments, like in Queensland.
- Red kangaroos tend to live in arid areas of Australia, mainly flat plains.
- Eastern and western gray kangaroos like to live among dense vegetation.
- Rat kangaroos make nests on the rainforest floor, hiding amongst the foliage.
How Did Kangaroos End Up in Australia?
The answer is a bit convoluted and involves Pangea. While we tend to think of marsupials as being mainly from Australia, that’s not true, even though the most famous ones are living it up as Aussies. Their origins are more along the lines of what is now North America.
At one time, there was a giant supercontinent that scientists refer to as Pangea. The tectonic plates on which the Earth’s land masses exist shifted and slid. They gradually moved the one big continent into the seven continents we know today: North America, South America, Europe, Asia, Antarctica, and Australia.
As the continents broke apart and drifted more to their current locations, Australia became isolated from the rest of the world. The animals and plants on the land began to evolve independently from those in other places, where land was more connected with nearby islands or even land bridges.
That doesn’t tell us where the marsupials came from, now does it? Well, some of the oldest evidence of marsupials is from North America.
These North American marsupials traveled to what is now South America. Scientists aren’t sure how: they either moved via island-hopping or a narrow land bridge that disappeared when the continents moved into their current locations.
Within South America, marsupials went wild and exploded into different habitats. There were saber-toothed carnivorous marsupials; there were tiny, shrew-like possums.
Eventually, over millennia, some of these species moved into Australia. Scientists used genetics and genotyping of various species, as well as the fossil record, to help prove the evolutionary relationships between marsupials in Australia and those in South America.
According to Robin Beck, a biology lecturer with the University of Salford, there were marsupials in the Americas for at least 70 million years before they ended up in Australia!
Marsupials began to evolve, fitting into different ecological niches. They had less competition from placental mammals in Australia, which are more common on Earth. Over millions of years, we ended up with a range of marsupials: Tasmanian devils, possums, Tasmanian tigers, wallabies, and, yes, kangaroos.
The Evolution of the Kangaroo
There’s more to the development of kangaroos in Australia. Some of these furry macropods can be 90 kilograms – about 200 pounds! And they evolved from tiny predecessors that weighed less than a few pounds.
The fossil record in Australia suggests that an ancestor similar to the musky rat-kangaroo came down from the trees that covered much of Australia. Many of these proto-kangaroos began to grow larger and thrive in various niches. For instance, the Procoptodon goliath was a giant ancestor of the modern kangaroo, weighing hundreds of pounds.
The red and gray kangaroos thrived in Australia for several reasons compared to their extinct ancestors. First, they were likely faster than their larger brethren and less likely to get caught by hunters. They also developed specialized teeth that allowed them to graze continuously on somewhat abrasive plant life in the grasslands of Australia.
Kangaroos are fascinating animals, and their evolution is only part of the story. Suppose the continents hadn’t separated when they did. Who knows what kinds of animals would have established themselves as essential parts of the landscape of Australia?