Invasive Species

Comprehension Activities


Cute little bunnies. Fluffy cats and tiny mice. They seem sweet and harmless, but these animals are causing havoc all over Australia. This is your invasive species Squiz Kids Shortcut—the podcast where we dive into the who, what, when, where, why and how of the big news stories. I’m Amanda Bower.

And I’m Bryce Corbett.

We’ve been hearing a lot in the news lately about a mouse plague in New South Wales, and feral pig problems all over the country. But Bryce, did you know that more than 3,000 species of animals have been introduced to Australia?

Cripes, that’s a lot!

Yep, and many of them threaten our delicate ecosystem. Today we’ll explore WHAT exactly an invasive species is, HOW they came to cause so much trouble, WHO is affected, and WHAT we can do about it.

Listen carefully – there’s a S’quiz at the end!


First of all, we’d better get our vocabulary straight. What exactly is an invasive species? Maybe you want to hit pause and brainstorm, or you can keep listening for some clues.

Whenever I come across a word I don’t know, I see if I can break it apart, or if it sounds like another word that I know. What does ‘invasive’ sound like to you, Bryce?

It sounds an awful lot like invasion, or invade. Like when one country invades another in a war, they basically march in and take it over.

Nailed it. How many of you thought that an invasive species might be a kind of animal that goes into a new ecosystem, and starts to take over? Well, you were right!

Now you’ve done it. You’ve introduced another word! “Ecosystem.”

I have a feeling we’ll be learning a lot of expert words today. I bet most of the Squiz Kids have learned about ecosystems in science already. “Eco” comes from ‘ecology’, which is the study of the relationships between living things and their environment.

So an ecosystem is made up of all the living and non-living things native to a specific area.

Exactly. And when an invasive species comes in – one that isn’t native to the area – it can cause BIG trouble. I know what you’re going to ask next…


How on earth can a cute little cat, for example, cause trouble?

Well, cats were introduced to Australia when English settlers came. And when some of those cats escaped and survived in the wild, they went from being purring pets to official problem pests.

I’ll bet they did! Cats are carnivores, meaning that they eat meat, and once they are out in the wild, they have to find a source of meat.

Exactly. And so they hunt native animals… causing more than 20 different Australian mammals to become extinct. Another 124 other species of birds and mammals are under threat from feral cats. Feral, by the way, is a word that describes domestic animals that have gone wild.

The Australian government says there could be up to six million feral cats all over the country, and they’re the single biggest threat to our native mammals. But they’re definitely not the only troublemakers.

Definitely not. One of the most infamous examples – infamous means famous for a bad reason – is the cane toad. Cane toads were intentionally introduced to Queensland in 1935, because sugar farmers hoped they would eat up the beetles that were chowing down on the sugar cane. Problem was, the beetles lived up high in the stalks, and the toads lived down low.

So they didn’t help at all?

Not even a little bit. And then they caused much bigger problems. Cane toads are apparently delicious to other animals, but also extremely poisonous. The Australian native animals didn’t know to avoid them, so cane toads spread all over the top end of Australia, leaving dead native animals in their path.

Oh, no. Why didn’t the Australian natives know to steer clear?

Well, they’d never seen a cane toad before, and didn’t know they were trouble. Part of the reason invasive species are a terrible problem is that 80% of Australia’s plants and animals do not exist anywhere else in the world, and so they don’t have any defences against these introduced animals.

Poor Australian animals. But humans are animals, too. Do invasive species cause problems for us?

Sure do. Let’s find out who cops the worst of it.


Hear that? It’s the rather horrifying sound of the mouse plague currently threatening farmers in New South Wales. It’s the worst mouse plague the state has seen in decades. Plagues – which describes an unusually large number of animals infesting a place – tend to follow droughts. Mice survive while it’s dry, and as soon as it starts to rain, they get to breeding. A single pair can produce 500 babies in one season!

Uh oh. Every parent knows that babies need to eat. What do all those mice munch on?

Our farmers’ crops. Mice eat the seeds, the fully grown plant, they’ll even invade the storage silos to munch on grain that has already been harvested. Even if they don’t eat everything that’s been stored, farmers have to chuck the rest, because the mice have pooed all over it.

That is disgusting.

Oh, that’s not the half of it. People have found mice in their homes, ceilings, and rubbish. Mice have overrun schools and interrupted Naplan exams. They are in the stuffing of armchairs, and even biting people in hospital beds.

NSW Farmers say the mouse plague may end up costing them $1 billion in lost winter crops for this year.

And let’s not forget the effect on their mental health, because they have mice around them. All. The. Time.

Are there other invasive species causing problems for humans?

Heaps. We reported recently on Squiz Kids Today that the behaviour of feral pigs puts the same amount of carbon dioxide into the Earth’s atmosphere as 1.1 million cars. Australia has 24 million of them.

Then there are Indian myna birds, which were introduced to Australia to control locust plagues, and are now on the World Conservation Union’s list of the world’s 100 worst invasive species. The birds spread mites and disease to humans, while also forcing native birds from their nests.

And there are rock pigeons, whose poo is so acidic that it damages human property, including historic buildings.

Crumbs, this is all sounding a bit awful, isn’t it? What can we DO about it?


Well, the first thing is to make sure that no more invasive species get into Australia. That’s why we have such a strict quarantine system.

Ah yes, I remember that before coronavirus, quarantine meant that we couldn’t bring fresh fruits and veggies into Australia, or even between some states, and that any animal coming into the country had to spend time in quarantine, being checked by vets.

Exactly. That kind of quarantine is an important defence.

And there are really simple things that cat owners can do, like keep their cats inside at night, and put a bell around their neck, so they can’t sneak up on native animals.

The government also has programs to try to control animals that have become feral, such as cats, pigs, mice, and other creatures. Those programs do include poison, but they have to be very careful, in case native animals or domestic animals like dogs and cats eat either the poison, or, say, the poisoned mice.

Clever scientists are also looking into lots of other inventive ways to deal with invasive animals… but that’s the subject of another podcast.

The S’Quiz

1. What type of animal was introduced to try to get rid of beetles eating sugar cane?
2. Why do NSW farmers have to chuck out their stored crops?
3. What simple thing can you put around your cat’s neck to help save local wildlife?