Australia is home to millions of kangaroos, the iconic marsupials that symbolize the country's wilderness. But these animals are also facing a major environmental challenge: a population boom that could lead to mass starvation and ecological damage.
Why are kangaroos booming?
Kangaroos have a "boom and bust" population cycle, meaning that their numbers can fluctuate dramatically depending on the availability of food and water.
When conditions are favorable, such as during wet seasons or La Nina events, kangaroos can breed rapidly and increase their numbers by tens of millions.
According to Dennis King from the Kangaroo Industry Association of Australia, the country is on the cusp of another kangaroo boom after three years of La Nina right down the east coast.
He said that the breeding cycle really speeds up when there is plenty of fodder for the animals.
However, when conditions turn unfavorable, such as during droughts or El Nino events, kangaroos can face severe food shortages and starvation.
Ecologist Katherine Moseby said that during the last drought, 80 or 90 percent of the kangaroos in some areas died.
She described how they were starving to death, going into public toilets and eating toilet paper, or lying on the road while their joeys were trying to feed, as per Phys.org.
What is the solution?
Moseby said that the kindest way to save kangaroos from this fate was to shoot them and harvest their meat, as a way of keeping their numbers in check, as per South China Morning Post.
She said that this would prevent the welfare issues that arise when kangaroos starve to death, and also help manage them as a resource.
Kangaroos are protected in Australia but the most common species are not endangered, which means they can be shot and killed in most jurisdictions with government permission.
Each year, as many as five million kangaroos are shot as part of a homegrown industry, which uses their carcasses for meat, pet food, and leather.
However, this solution is not without controversy. Animal rights activists have denounced the commercial culling of kangaroos as a "cruel slaughter" and pressured global sportswear giants such as Nike and Puma to phase out the use of kangaroo leather.
They argue that kangaroos are native animals that deserve respect and protection and that shooting them is inhumane and unsustainable.
Some politicians in Oregon, where Nike was founded, introduced a bill earlier this year that would outlaw the use of any part of a dead kangaroo.
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What is the history of kangaroo evolution?
Kangaroos are among the most recognizable animals in the world, but they also have a unique evolutionary history.
They belong to a group of mammals called marsupials, which give birth to underdeveloped young that complete their development in a pouch.
Kangaroos are thought to have evolved from tree-dwelling ancestors that came to live on the ground about 20 million years ago.
Some of these ancestors grew to become giant kangaroos weighing over 250 kilograms, but they went extinct about 40,000 years ago. Others evolved into the modern kangaroos we see today.
One of the most distinctive features of kangaroos is their hopping locomotion, which allows them to move fast and efficiently across open landscapes.
However, it is still not clear why they started hopping in the first place. Some researchers have suggested that hopping evolved as a response to changing climate and vegetation patterns in Australia, while others have proposed that it was a result of competition with other herbivores or predators.
A recent study by Aidan Couzens and Gavin Prideaux from Flinders University challenged the conventional view that kangaroos diversified in response to drying during the Miocene epoch (23-5 million years ago).
They analyzed over 1600 marsupial tooth specimens dating back 25 million years and found that kangaroos had short teeth throughout the Miocene, indicating that they ate soft leaves and shrubs.
It was not until the Pliocene epoch (5-2 million years ago) that they evolved teeth with higher crowns, suitable for eating tough grasses. This suggests that kangaroo diversification was driven by grassland expansion rather than aridity.
The study by Couzens and Prideaux also revealed that kangaroos underwent a rapid adaptive radiation during the Pliocene, giving rise to the modern groups of red kangaroos, grey kangaroos, wallaroos and wallabies.
They found that these groups diversified in different regions of Australia, adapting to local environmental conditions.
For example, red kangaroos are adapted to arid and semi-arid habitats, while grey kangaroos are more common in temperate and coastal areas.
The study also showed that kangaroo diversity declined during the Pleistocene epoch (2 million-10,000 years ago), coinciding with the arrival of humans and the extinction of many large mammals in Australia.
The researchers suggested that human hunting and habitat modification may have contributed to the decline of kangaroo diversity.
The study by Couzens and Prideaux provides a new perspective on kangaroo evolution and highlights the importance of fossil evidence for understanding the history of life on Earth.
It also shows that kangaroos are not only a symbol of Australia's wilderness, but also a product of its dynamic and changing environment.
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