Indeed, feral cats and foxes have significantly contributed to the extinction of numerous Australian mammals.

 

The unique mammal diversity of Australia has evolved over millions of years of seclusion, resulting in species not found anywhere else globally, including platypuses, koalas, and wombats.

Regrettably, Australia holds the unfortunate title of the highest number of mammal extinctions worldwide.

Since European settlement began 238 years ago, around 40 species have disappeared, with nearly 80 more now at risk. It is critical to comprehend the factors that led to these extinctions and the ongoing decline of mammal populations.

Scientists have accumulated substantial evidence over the years showing that predation by introduced species like cats and foxes has significantly contributed to this issue.

Australian mammals have coexisted with other predators, such as wedge-tailed eagles and dingoes, for thousands of years. However, foxes and cats pose a unique threat as incredibly adept and adaptable hunters, unlike any predators previously encountered by these mammals.

Recently, some scientists have started to question whether these introduced predators are truly to blame. In our latest study, we present clear evidence linking foxes and cats to these extinctions.

For example, the species that have gone extinct are predominantly small to medium mammals, which are the preferred prey of these predators. When mammals are reintroduced to areas that are free from foxes and cats, their populations often thrive.

Controversy in conservation

Last year, studies were conducted that cast doubt on the evidence supporting the claim that feral cats and foxes have played a role in Australian mammal extinctions, which indirectly challenges their contribution to the decline of other threatened mammal species.

These studies were based on three key assumptions concerning both extinct and surviving mammal populations. If cats and foxes were responsible for the extinctions, they suggested the following conditions should be met:

The last known sighting of an extinct mammal should date after one or both of these predators arrived in that area.

Efforts to manage and reduce fox and cat populations should lead to increases in native mammal populations in those areas.

The presence of abundant cats and foxes should correlate with lower numbers of native mammals.

After evaluating these premises, the researchers concluded that the belief in foxes and cats causing extinctions has gained acceptance with insufficient evidence.

This study generated significant discussion within the conservation community, as it challenged well-established knowledge and questioned whether the foundation of the evidence was robust enough to support control measures for feral cats and foxes.

As professionals with extensive experience in safeguarding threatened Australian mammals and other wildlife, we felt it was our responsibility to scrutinize their findings.

Debate and counterarguments are vital in testing, refining, and solidifying scientific understanding, as well as in informing sound conservation practices. Although it may appear to be an academic dispute, it carries tangible implications for the real world.

The preservation and recovery of a large portion of Australia’s native mammal species hinge on the management of cats and foxes. Numerous recent successes in rescuing native species from the verge of extinction can be attributed to the elimination of these predators.

If we abandon this goal due to claims that feral cats and foxes are mere bystanders, we face the peril of swiftly losing many at-risk species.

What actions were taken?

A striking assertion from research conducted last year suggested that certain Australian mammal species might have become extinct prior to the arrival of foxes and cats in the region. If this hypothesis holds true, then cats and foxes cannot be blamed for their extinction.

Cats were brought over with the First Fleet in 1788, with many additional introductions following. By the 1890s, feral cat populations had proliferated throughout the continent. Foxes were introduced later, first arriving in southeastern Australia during the 1830s. Over the following decades, they also expanded their range across much of the continent.

We conducted a re-analysis of historical data and discovered that the last known sighting of a now-extinct native mammal in a given area consistently occurred after the introduction of cats. The timeline for foxes is less defined, but this ambiguity makes sense considering that the earlier presence of cats may have already led to declines.

Moreover, the true extinction date can often take place well after the last recorded sighting, particularly in remote and thinly populated regions of Australia.

Both First Nations peoples and Europeans have observed and documented numerous instances of native mammal species vanishing from regions shortly after the arrival of one or both non-native predators.

Fate offers additional support for this observation. Several mammals have been entirely eliminated from their mainland habitats yet have persisted on islands that were never inhabited by cats and foxes.

For example, all mainland populations of the greater stick-nest rat have vanished. However, this species continues to exist because it had an island population. Conversely, the lesser stick-nest rat lacked a population on an island and is now extinct.

Do control measures for foxes and cats yield results?

The authors contend that controlling fox and cat populations does not lead to an increase in endangered mammals. However, this conclusion may result from a misunderstanding of the data from feral cat and fox management initiatives. Not all control efforts effectively lower cat numbers over extended periods, or they may fail altogether.

Instead, more definitive evidence can be obtained from observing what occurs in safe havens—such as islands or enclosed regions where foxes and cats are entirely barred.

In these protected areas, threatened mammal species typically show marked increases, while similar sites without such exclusions see declines in these species.

Eastern barred bandicoots thrive on Phillip Island in Victoria, which is free of foxes, and hare-wallaby populations are recovering on Dirk Hartog Island in Western Australia after the removal of feral cats.

The assumption that native mammals would generally be less prevalent in areas where cats and foxes are abundant does not always apply.

Following periods of favorable rainfall in inland Australia, populations of both native mammals and feral predators tend to rise. Conversely, during droughts, the numbers of both predators and prey decline.

Challenging realities

The initial evaluation and our updated study exist within a wider framework. Some individuals argue that the effects of non-native species have been exaggerated, claiming they should be considered an authentic component of Australia’s ecosystems. However, scientific data and conservation results do not back this notion.

As one of merely 17 highly diverse nations, Australia is home to roughly 8 percent of the planet's biodiversity. Safeguarding our distinct species poses significant challenges. However, the responsibilities for conservationists and decision-makers will become increasingly difficult if feral cats and foxes are allowed to continue their predation unchecked.

Regrettably, lethal measures are essential for the protection of numerous species that are on the verge of extinction. Such actions must be carried out as humanely as possible and must be publicly defended. Failing to act will result in a greater number of extinctions.