There are many dangerous animal species in the world. Some are dangerous because they transmit diseases, such as mosquitoes that cause malaria. Others are dangerous due to their lethal venom.
Interestingly, Australia has only 66 venomous species, while Mexico has 80 and Brazil has 79. However, Australia is home to the most dangerous and lethal venomous species. The inland taipan, box jellyfish, stonefish, blue-ringed octopus, and cone snail are among the top 10 most venomous animals in the world, all residing in Australia.
Inland Taipan – The most venomous snake in Australia. (Photo: Elliot Budd).
Even more impressively, Australia is home to 20 of the 25 most venomous snake species in the world, including all the species in the top 11. The most venomous land snake in the world, the inland taipan (Oxyuranus microlepidotus), is found nowhere else on Earth except Australia. It is also known as the fierce snake and carries enough venom in a single bite to kill 250,000 mice at once.
But why does Australia have so many highly venomous animal species? Theconversation will explain this question, so let’s take a look.
180 Million Years Ago…
First, we need to turn back the clock to 180 million years ago. At this point in history, Africa, South America, India, Australia, and Antarctica were all connected (known as the supercontinent). This landmass gradually separated: Africa and South America drifted apart first, followed by India and Madagascar 40 million years later. Australia and Antarctica finally split about 100 million years ago.
Today, venomous snakes are found in all these areas—except Antarctica, which is too cold for them to survive. On the original combined landmass, it is believed there was a population of ancestral venomous snakes living on the supercontinent. They gradually separated as the landmasses broke apart.
Venomous snakes found all over the Earth, except Antarctica. (Illustration: Raúl Gómez / Scitechdaily).
While other continents have various snake species, snakes in Australia mostly belong to one group, called elapids. This group of snakes specializes in injecting venom into their prey through fixed hollow fangs.
Other continents have some ancestors that may or may not be venomous, but all 140 species of land snakes and 30 species of sea snakes in Australia evolved from a venomous ancestor.
Some species that were already venomous simply became trapped in Australia when it became an isolated landmass. Venomous arthropods found there include trap-jaw ants (genus Odontomachus), which can deliver a painful bite, but these insects also exist in other tropical and subtropical regions around the world, not just in Australia. Similarly, the Australian bulldog ant (genus Myrmecia) can both sting and bite simultaneously; it is among the most dangerous ants in the world and is believed to have killed 3 people since 1936, according to the Guinness World Records. These venomous ant species were present in Gondwana at the time of the split and remained in place as Australia became its own continent.
As for spiders, the funnel-web spider (genus Hadronyche and Atrax) is the only species in Australia that can kill a person with its venomous bite. According to the Australian Museum, the male Sydney funnel-web spider (Atrax robustus) is believed to have killed 13 people, although no human fatalities have been recorded since the antivenom was introduced in 1981. An Australian widow spider, the redback spider (Latrodectus hasselti), can also kill with its venomous bite.
Similarly, venomous cephalopods, including squids, octopuses, and cuttlefish, have existed for up to 300 million years.
Evolution to Survive
Imagine a snake using venom to kill its prey. If all snake species had the same venom, they would only be able to kill prey of a certain type or size.
However, there is often a difference in the potency of venom among snake species. This diversity is similar to how humans have different heights or foot sizes.
Clockwise from left: Blue-ringed octopus, box jellyfish, cone snail, and stonefish – The top 10 world “killers” with strong venom, all in Australia. (Photo: Internet)
Thus, a snake with slightly stronger venom can kill prey (more varied in size) that other snake species cannot. It will be able to eat more food—enough to survive and reproduce, passing strong venom to its offspring. These snakes will have a better chance of survival than those with weaker venom, making strong venom increasingly common. This is what we call evolutionary process.
Since every meal is valuable, especially because some snake species live in hot, dry environments where prey is scarce, the venom must be extremely effective to ensure that prey does not escape or harm the snake.
And as prey develops ways to resist the effects of venom, snakes are forced to evolve ways to make their venom even stronger.
It seems that Australia has the most dangerous animals because their unique ancestors were also dangerous, albeit not as potent (they have become stronger through evolution to adapt to their living environment).
However, very few Australian animals actually cause death to humans. So, while Australia has many of the deadliest venomous animals in the world, it is unlikely that you will be harmed by them, especially since they only bite humans when they feel threatened.
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