But since 1985, there have been no confirmed records of the species, \u201cdespite surveys and many studies,\u201d notes the species\u2019 latest conservation assessment. That assessment, for the IUCN Red List, concludes the species is now officially extinct<\/a>. It was last assessed in 2016<\/a> as critically endangered (possibly extinct).<\/p>\n The shrew\u2019s decline on the island likely started in the early 20th century when a visiting ship accidentally introduced black rats<\/a> (Rattus rattus) within bales of hay.<\/p>\n Two of the island\u2019s endemic rat species, found nowhere else on Earth, were soon wiped out, likely from a blood-borne parasite transmitted by the black rats. Maclear\u2019s rat (Rattus macleari) and the bulldog rat (Rattus nativitatis) were last recorded before 1908.<\/p>\n The parasite also likely played a role in decimating populations of the Christmas Island shrew, researchers say. There are just four confirmed records of the shrew in the 20th century: two in 1958, one in 1984, and the last in 1985. These observations suggested that \u201ca very small proportion of the shrew population must have survived\u201d the parasite outbreak, the IUCN assessment notes.<\/p>\n \u201cHowever, this small population is likely to have been highly vulnerable to the many other widespread threats that accompanied or followed settlement of the island, including feral cats, clearing, black rats, yellow crazy ants and wolf snakes,\u201d the assessment adds.<\/p>\n Some of these invasive animals likely also wiped out the Christmas Island pipistrelle<\/a> (Pipistrellus murrayi), a tiny bat species last recorded in 2009 and declared extinct in 2017.<\/p>\n Blyth\u2019s flying fox<\/a> (Pteropus melanotus), a fruit bat, is the last remaining native mammal species on Christmas Island. However, it, too, is under threat from growing settlements, agriculture and invasive species.<\/p>\n Woinarski writes that the case of the Christmas Island shrew is \u201ca reminder of the enormity of the challenge of preventing further extinctions.\u201d<\/p>\n \u201cI hope the Christmas Island shrew is not extinct; after all it has defied previous calls of its demise. Perhaps somewhere, a small furtive family of shrews are hanging on, elusive survivors, secure in the knowledge of their own existence and waiting to prove the pessimists wrong,\u201d he adds.<\/p>\n Banner image: View of Christmas Island, Australia. Image by David Stanley via Wikimedia Commons<\/a> (CC BY 2.0<\/a>)<\/p>\n <\/p>\n