A researcher says the long-suspected extinction of the mouse-sized mammal is "another stain" on Australia's environmental record.

In short:

The Christmas Island shrew has been added to an international “red list” of extinct species.

Only four sightings of the mouse-sized mammal have been reported in the past 120 years.

What’s next?

The listing takes Australia’s tally of extinct mammal species to 39 since colonisation.