Calling species ‘invasive’ – and culling them – isn’t done lightly. But it matters to Australia’s threatened species

by bpckle | Oct 27, 2026 | In the Media

It may sound abstract, but distinctions between “native”, “introduced” or “invasive” species can often be life or death. Species considered invasive in Australia – such as European rabbits and feral pigs – are often culled, while most native animals are generally left alone.

Debate over these terms doesn’t usually go mainstream. But this month was different. On October 13, independent Senator David Pocock brought a motion in federal parliament calling for a long-term plan to “protect Australia’s landscapes and wildlife from invasive species”.

In response, Greens Senator Mehreen Faruqi took aim at the term “invasive”, saying:

There’s no need for labelling introduced species as invasive in a way that
blames animals for the man-made problems raised by this motion. Language matters. Animals are not villains to be shot or obstacles to be poisoned to death.

As an ecologist and conservation scientist, the debate spoke to me about how important it is to explain why “invasive” species are given this title, the damage they can do and why many need to be eradicated or their numbers greatly reduced.

If we stop trying to control some invasive species, we risk condemning even more native animals to extinction and worsening Australia’s environmental decline.

Every Australian knows common myna birds are bad, rabbits are worse and feral cats kill native animals unchecked.

But how do we decide what makes an introduced species “good” or “bad” – and will we ever concede that some species are here to stay?

Our new series on invasive species explores these questions.

Why do these terms matter?

Conservationists and authorities commonly use four words – introduced, feral, invasive and pest – to describe species present in Australia. Definitions can differ and there is debate over their exact meaning. But their broad meanings are clear:

Introduced species (also known as alien, exotic or non-native)

An introduced species has been moved by humans to areas outside their known natural historic range. This can be accidental (think black rats on ships) or intentional (deer species introduced for hunting). Native species – such as the superb lyrebird – can also be considered introduced when moved to new locations in the same country.

Feral

This term refers to introduced domesticated species that now have wild populations independent of people. Feral cats, goats, horses, pigeons, pigs and camels are common examples in Australia.

Invasive

Invasives are introduced species whose presence is concerning, either due to their clear (typically negative) impact on ecosystems or their rapid spread after introduction. Not all introduced species are considered invasive, but all invasive species are introduced.

Pest

A species is considered a pest if it damages things humans care about, such as crops. Typically, pest species are relatively abundant. Both native and non-native species can be pests.

While these terms have some overlap, they are generally not interchangeable. They help inform environmental decision-making and guide conservation efforts – including culling or biological controls.

Native species matter

For millions of years, Australia was relatively isolated. This shaped the evolution of the continent’s extraordinary array of native species. Most plants, animals and other lifeforms here are found nowhere else on Earth.

These species have a right to persist in the face of European colonisation, land clearing and waves of introduced species.

Native species are vital to healthy, functioning ecosystems. They support our economy and national identity, bring us immense joy and have deep cultural meaning for First Nations peoples.

Why do we need lethal control?

In her response, Faruqi stated:

Protecting our precious environment does not require inhumane treatment and cruelty to sentient animals, whether they’re native or introduced species. […] For decades, successive governments have culled and killed introduced species, and yet native species are in a worse position today.

She isn’t alone. Some people feel uncomfortable with killing some species to save others.

The problem with this is that if we do nothing, more and more native species will face extinction.

Globally, ecologists consider introduced and invasive species to be one of the greatest threats to nature’s wealth of species, alongside destruction or alteration of habitat, climate change, disease and pollution.

Two invasive predators – foxes and feral cats – have been implicated in the recent extinctions of many native Australian mammal species. Invasive rabbits are pests on farms, devastate many native plants and can bolster cat and fox populations.

Conservationists seek to do the least harm, maximising animal welfare while still keeping native species and ecosystems intact. But this brings a difficult choice. Sometimes, there’s a need to kill some species to save others.

If we have to make these decisions, we must ensure they have strong scientific justification. Any lethal control program must be able to clearly state its objectives prior to commencing, and measure and report its outcomes, so we can see if it worked or not, and why.

No control, no numbats

The numbat was once widespread across Western Australia. But predation by cats and foxes, habitat destruction via land clearing and changes in fire management drove the charismatic termite-eater to the brink of extinction in the 1970s.

But their numbers have now rebounded. Numbats are no longer endangered.

What saved the numbat was the difficult decision to use poison baits and traps to cut the numbers of feral cats and foxes in areas where numbats still survived, alongside establishing predator-free, fenced sanctuaries and breeding programs.

Conservationists have had many similar successes across Australia. Scores of fenced sanctuaries and islands are helping many native species recover in the absence of non-native predators.

After the last foxes were removed from Victoria’s Phillip Island, little penguin numbers rose, while eastern barred bandicoots and bush stone-curlews were successfully brought to the island after being wiped out by predators and other pressures elsewhere.

When invasive species pressure lifts, native species can rebound

Faruqi’s claim that native species are in a worse position today is inaccurate, as Australia’s threatened mammal index shows.

Where authorities control invasive predator numbers and take other management actions, native mammals do far better. Populations of these species fell about 20% and largely stabilised between 2000 and 2022. By comparison, populations of threatened mammals without this management intervention fell more than 50% over the same period.

It’s true Australia’s overall conservation trajectory is dire and deteriorating. But that’s not a reason to stop controlling invasive species – quite the contrary.

Invasive species are only trying to live. But their success comes at a potentially very real cost to the survival of native Australian species.

We have a responsibility to try and solve the problems caused by the introductions of species by earlier generations. Letting cats, deer, foxes, horses, pigs, and other invasive species run riot is no answer.

Euan Ritchie receives funding from the Australian Research Council, the Department of Energy, Environment and Climate Action, and Natural Hazards Research Australia. Euan is a councillor with the Biodiversity Council, a member of the Ecological Society of Australia and the Australian Mammal Society, and President and Fellow of the Australian Mammal Society.

The power of poo: why conservationists love animal scat

by bpckle | Oct 26, 2026 | In the Media

I never thought my shoelaces would get stolen.

As a wildlife researcher, I’m used to early alarms and long days out in the field. But one morning, before my team headed out to trap and monitor Tasmanian devils, I woke up to find my boots destroyed and stripped of their laces.

It didn’t take us long to find the culprit. In a trap not far from our campsite sat a cheeky older devil – and her scat that had several inches of shoelace curled up in it.

Scat is the scientific term for wild animal poo. Scat comes in all shapes and sizes, from the cube-like droppings of wombats to the tiny round pellets that rabbits leave behind.

Studying scat may help identify a shoelace thief, but it is also a vital part of species conservation. Let’s unpack why.

Searching for scat

While conducting research into the diet of Tasmanian devils, we have spent countless hours searching for scat, in order to pull it apart and study its contents.

Traditionally, researchers find scat by conducting systematic grid searches. This involves setting up transects, a type of narrow path, that stretch across a study area and allow scientists to pick up any scat they see.

More recently, researchers have enlisted the help of scat detection dogs. With their millions of olfactory receptors – the reason for dogs’ superior sense of smell – these dogs are trained to sniff out scat. In one study, these dogs found about 53% more koala scat than their human counterparts.

Why scat matters

But why are researchers searching for scat in the first place?

Scat is a waste product that most people would steer clear of. But for scientists, scat is a rich reservoir of information, particularly about our most vulnerable animals.

Population size

Threatened species exist in low numbers and can be quite elusive. This makes them difficult to find, let alone monitor.

However, studying scat allows scientists to not only determine if a species lives in a certain area, but estimate how many of them are present.

Gut health

Scat also gives us clues about what animals are eating and how healthy their gut microbiome is.

The gut microbiome is the collection of bacteria and viruses living inside an animal’s digestive system that supports digestion and immunity. An animal’s gut microbiome can change depending on where they live. For example, captive Tasmanian devils have significantly fewer bacteria in their scat than wild devils. But when released, these captive animals are able to gain new bacteria quickly and adjust to living in a wild environment.

An animal’s gut microbiome is largely shaped by what it eats. In the case of Tasmanian devils, that includes just about everything. From shoelaces and wetsuit zippers to frogs, fish and even sheep, devil scats are practically their own ecosystem. By tracking what devils eat, scientists can meet the nutritional needs of captive animals. They can also identify which species devils most commonly eat, including wallabies and birds, and take measures to protect these prey species, such as setting up exclusion fences.

Disease risk

Scientists most commonly monitor the spread of disease by trapping individual animals and taking blood or swab samples, similar to COVID tests for humans. But this type of testing can be uncomfortable for animals.

Studying scat is an easy way to detect infectious diseases. Scat collection is an alternative, non-invasive way of detecting any harmful bacteria, viruses and parasites. That’s because, like humans, animals’ bodies shed infectious material in multiple ways, including by producing scat. For instance, researchers can identify koalas with chlamydia just by examining their scat. The results are just as accurate as invasive swab samples.

Genetic health

As scat moves through an animal’s body, it collects cells that line its gut. Researchers can extract DNA from these cells to see how diverse that animal’s genes are. This variation is known as genetic diversity and is why no two animals – or humans – look and behave exactly the same.

In general, the more genetic diversity an animal or species has, the better. That’s because genetic variation allows animals to adapt to threats, such as disease and climate change, and ultimately survive.

Using scat DNA, researchers have successfully assessed the genetic diversity of the greater bilby, studied the breeding and movement patterns of ghost bats across remote northern Australia and identified that snow leopards do not travel across breeding sites in the Tibetan plateau.

The power of poo

Scat is a powerful, and perhaps unlikely, conservation tool. There is no other substance that can tell you so much about an animal you may never actually see.

However, studying scat does have limitations. When exposed to the elements, the DNA in scat can quickly degrade, making it harder to extract reliable data from it. Researchers are investigating ways to keep scat fresh out in the field. However, more work is needed before scientists can rely on scat collection alone, instead of blood and tissue samples.

Studying scat may not appeal to everyone. But for researchers like us, it is a fascinating and uniquely hands-on way of protecting our precious wildlife.

Elspeth McLennan receives funding from the New South Wales and Australian governments.

Carolyn Hogg receives funding from the Australian Research Council, including through the ARC Centre of Excellence for Advanced Peptide and Protein Engineering, the New South Wales government and the Australian government. She is affiliated with the Biodiversity Council.