Christmas Island shrew: one of Australia’s most enigmatic animals

Name:  Christmas Island shrew (Crocidura trichura)

Size: Length head-body 70mm; tail 70-80mm. Weight 4-6g.

Diet:  Invertebrates

Habitat/range:  Occurs (or occurred) only on Christmas Island in the Indian Ocean; mostly in rainforests.

Conservation status: Critically Endangered.

Superpower/fun fact: Shrews are oddballs. One quirky feature is that if a mother shrew wants to move her young from their nest, she orders them into a ‘shrew caravan’ or long conga line of interconnected shrews. The mother leads off with the first young biting her tail, with each successive young clamping its jaws on the tail of the one in front of it.

Christmas island shrew.
The Christmas Island Shrew was featured in an Australian stamp series in 2011.

The Christmas Island shrew is one of Australia’s most enigmatic animals. The world has many shrew species, but this is the only one that occurs in Australia. This happenstance is largely due to a juxtaposition of colonial history and geographic quirk – Australia owns an island which is partly Asian in its biodiversity.

Most shrews are very small (mouse-size or smaller), with a pointy snout and small eyes. Mostly, they trundle through the forest floor at night, snuffling for invertebrates. On mainland Australia, the marsupial planigales fill a comparable niche.

Shakespeare gave shrews a bad name, with ‘shrewish’ becoming a metaphor of meanness and ill temper (misogynistically, mostly in women). More so, they are feisty.

Our only shrew may be no more. If so, it is an extinction that has been little recognised or mourned. It was exuberantly abundant when Christmas Island was first discovered and settled in the 1890s. At that time, naturalists remarked ‘this small shrew-mouse was very abundant in the woods, and their short shrill squeak was often heard all round as one stood quiet among the trees’ and ‘this little animal is extremely common all over the island, and at night its shrill shriek, like the cry of a bat, can be heard on all sides’: a strange cacophony of shrews.

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But the forest is no longer filled with shrew squeaking. Within a few years of settlement, black rats were accidentally introduced to the island, and the fleas they brought with them carried a pathogenic trypanosome that very quickly wiped out Christmas Island’s two strange endemic rats, and killed off the shrews.

By 1909 (just a decade after their discovery), they were considered extinct. But they weren’t. In 1958, nearly sixty years after the preceding sighting, two shrews happened to be found. Then no more (and they were thought extinct again) until more than 20 years later, two more turned up (in 1984 and 1985). None have been seen since. Over the past 30 years, many people have looked; but if the shrews still exist, they have proven elusive. It says something of the mystery of this species that only four individuals have been reported in the last 120 years. How rare can you get? This little-known Australian mammal has been hovering on the tightrope above the abyss of extinction for more than 100 years now.

Some sources consider them, again, as extinct. But the Christmas Island shrew has clearly shown some resilience, persisting in tiny numbers at least 80 years after almost all its population was extirpated, and re-appearing after two periods when it was considered extinct.

Are they still there? I hope so.

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