And then there were none: Australia’s only shrew declared extinct | John Woinarski for the conversation

It’s official: Australia’s only shrew is no more.

The latest edition of the International Union for Conservation of Nature’s Red List, the world’s most comprehensive inventory of extinction risk, declared the Christmas Island shrew extinct.

The news may not seem momentous. After all, most Australians know nothing about shrews and are unaware that this species is part of our native wildlife.

But the extinction of the shrew brings to 39 the number of Australian mammal species that have disappeared since 1788. This is far more than for any other country. These losses represent approximately 10% of all land mammal species in Australia before colonization. It is a deplorable record of destruction of an extraordinary heritage.

So, what are shrews?

Shrews are small, long-nosed insectivorous mammals, many species of which are widely distributed in Asia, Africa, Europe, and the Americas. In mainland Australia, similar roles are fulfilled by small, unrelated marsupials such as dunnarts, antechinus, planigales and ningauis, which themselves are not widely enshrined in our national consciousness.

Many people only know about shrews from Shakespeare. Mixing misogyny and zoophobia (an intense fear of animals), he uses the name of this harmless animal to describe a garish, always plaintive and grating caricature of women. The offensive term has spanned the ages, draining sympathy and interest in the animal.

The story of the Australian shrew

It must have been a grueling journey. Tens of thousands of years ago, a small family of shrews (or a pregnant female) sailed on floating vegetation from the islands of what is now Indonesia. By chance, they landed on uninhabited Christmas Island, now an Australian territory about 1,500 km west of the mainland. These pioneers, lucky or reckless, gave birth to Australia’s only species of shrew.

For many years, the Christmas Island shrew thrived. When European naturalists first visited Christmas Island in the 1890s, at the time of its colonization, they noticed:

This small animal is extremely common throughout the island, and at night its high-pitched, bat-like cry can be heard on all sides.

Change came quickly thereafter. In 1900, black rats were accidentally introduced as stowaways on hay bales. Worse still, these rats were infested with trypanosomes, a cellular parasite. These trypanosomes quickly spread to the island’s two native rat species (and probably to the shrew).

Christmas Island’s long isolation had cocooned its native mammals, leaving them with no resistance to new diseases. Within a year, island residents began seeing many dying rats stumbling across the forest floor.

By the time naturalists next visited the island in 1908, both native rat species and the Christmas Island shrew were thought to be extinct. Subsequently, many other endemic animals also became extinct or suffered severe declines due to the introduction of cats and invasive species of ants, snails, plants, giant centipedes, birds and snakes.

This is a trend that has happened repeatedly in islands around the world. Introductions of plants and animals have disrupted island ecosystems, and as a result, endemic island species account for a disproportionate number of extinctions worldwide.

Defying extinction?

But the shrew survived. After going unnoticed for more than 50 years, two survivors were captured in the 1950s as bulldozers cleared a patch of rainforest for mining. The shrews were released and the discovery was not reported until several years later.

Then, nothing for another 30 years. In December 1984, biologists Hugh Yorkston and Jeff Tranter were clearing a trail in the rainforest and came across a live female shrew in a clump of fallen bird’s nest ferns. They kept the shrew in a terrarium for 12 to 18 months, diligently catching grasshoppers to feed it.

At the time, they did not view this as a final opportunity to conserve the species through a captive breeding program. When, by extraordinary coincidence, a male shrew was found alive a few months later, in March 1985, he was kept in a separate terrarium. The female was docile but the male was aggressive. He also seemed ill.

Whatever the reason, there was no introduction, no consumption, and no baby shrews. The male died about three weeks after his capture while the female lingered alone.

No more shrews left

Since 1984, no sightings have been recorded. This means only four Christmas Island shrews have been reported in more than 120 years.

Almost no information on the biology of this species has been published, apart from the single sentence written by the naturalist Charles Andrews in 1900:

It lives in holes in rocks and in tree roots and appears to feed mainly on beetles.

There are few photos. However, insights into the nature of the last known shrew can be seen in a beautiful sketch by park ranger, naturalist and artist Max Orchard.

Nearly 40 years after the death of the last known individual, two recovery plans have been developed, outlining the actions needed to conserve the species. Targeted searches were carried out. But no shrews came to benefit from these plans.

The most telling evidence of their extinction is the absence of shrews in the stomach contents of hundreds of wild cats shot over the past few decades.

While the shrew clearly survived until the 1980s, this decade saw the arrival of another threat, the Asian wolf snake. This snake quickly spread across the island, most likely causing the extinction of the island’s endemic microbat, the Christmas Island pipistrelle, in 2009, as well as most of the endemic lizards. The arrival of the snake probably also sounded the death knell for any remaining shrews.

We must redouble our efforts to prevent extinctions

Extinction can be difficult to prove, especially for a species as enigmatic as the shrew. It is dangerous to categorize a species as extinct when it still survives. This misclassification has been called “Romeo’s error”, in which the formal recognition of a species as extinct can result in the withdrawal of funding or protection, and therefore increase the likelihood of actual extinction.

In 2022, the Australian Government, through then Environment Minister Tanya Plibersek, committed, admirably, to preventing further extinctions. Although official recognition of the shrew’s extinction came after this commitment, the last shrew probably died one to two decades earlier.

The loss of the shrew reminds us of the enormity of the challenge of preventing further extinctions, the diverse ways in which these losses can occur, the need to seize opportunities to protect rare species, and the importance of national and political commitment to prevent extinction.

I hope the Christmas Island shrew is not extinct; after all, he defied previous calls for his demise. Maybe somewhere, a small, furtive family of shrews is hanging on, elusive survivors, sure of their own existence and waiting to prove the pessimists wrong.

Hugh Yorkston, Jeff Tranter and Paul Meek contributed to this article.

• John Woinarski is Professor of Conservation Biology at Charles Darwin University.

• This article was originally published in Conversation