Mammal extinction by introduced infectious disease on Christmas Island (Indian Ocean): the historical context

Abstract

Two endemic rat species, Rattus macleari and R. nativitatis, went extinct on Christmas Island more than a century ago, contributing to an unenviable record of mammal extinctions in Australia. This paper provides the historical context for the extinctions, and shows they were inextricably linked to the expansion of the island's nascent phosphate industry. The endemic rats were killed off by a disease introduced with black rats R. rattus, which according to the mining company manager Captain Samuel Vincent, were bought to the island by the SS Hindustan that arrived in December 1899. However, historical sources including a photograph held in the National Archives of Australia, together with newspaper shipping intelligence and archival correspondence, all suggest that Captain Vincent was actually referring to the SS Hindoustan that visited the island in early September 1900. This shortens the period between alien introduction and endemic extinction from five years to four years. At the time, the arrival of black rats was noteworthy not for their impact on the native rats, but because they frustrated attempts at growing fresh food and were implicated in the appalling death toll of Chinese coolies during an outbreak of beriberi. This research corrects and adds to the century-old and widely reported account of these extinctions, and places the introduction of R. rattus in a broader historical context.

Molecular identification of the Trypanosoma (Herpetosoma) lewisi clade in black rats (Rattus rattus) from Australia

“…Recent research has confirmed Durham's initial reports and concluded that the rapid decline and extinction of the two endemic rat species was correctly attributed to infections with T. lewisi (Wyatt et al 2008). A review of historical records demonstrated a rapid extinction event following the arrival of black rats on the island in September 1900 and an absence of native rat sightings by October 1904 (Green 2014). While there is strong support for the placement of the trypanosome species responsible within the T. lewisi clade, the nature of the ancient DNA study by Wyatt et al (2008) using museum specimens meant that only a short fragment of the 18S rRNA gene was amplified.…”

“…A recent study by Dybing et al (2016) have also been carried out at North Head by the Australian Wildlife Conservancy. While there is no evidence of spill-over of trypanosomes within the T. lewisi clade to native species to-date, ongoing monitoring of populations is encouraged given the historical significance of this parasite with respect to native animal declines (Wyatt et al 2008;Green 2014).…”

Molecular identification of the Trypanosoma (Herpetosoma) lewisi clade in black rats (Rattus rattus) from Australia

“…In addition to being home to endangered populations of long-nosed bandicoots (Perameles nasuta) and little penguins (Eudyptula minor), reintroductions of native fauna species, such as bush rats (Rattus fuscipes), eastern pygmy possums (Cercartetus nanus) and brown antechinus (Antechinus stuartii), have also been carried out at North Head by the Australian Wildlife Conservancy. While there is no evidence of spill-over of trypanosomes within the T. lewisi clade to native species to-date, ongoing monitoring of populations is encouraged given the historical significance of this parasite with respect to native animal declines (Wyatt et al 2008;Green 2014).…”

Endemic species of Christmas Island, Indian Ocean

“…Ixodes nitens is known only from a few individuals collected from the last specimens of Rattus macleari, before it became extinct between 1901 and 1904 (Durham 1908;Green, 2014), so the tick presumably became extinct at the same time (Mihalca et al 2011;Colwell et al 2012). Ariadna natalis has not been recorded since the type collection in 1897-98.…”

“…The last specimens of the endemic Maclear's rat Rattus macleari were collected by Durham in 1902(Durham 1908Pickering and Norris 1996;Green 2014). Fleas collected from these specimens were described as a new species, Xenopsylla nesiotes (Jordan and Rothschild 1908).…”