Bulldog Rat - Rattus nativitatis

A Bulldog Rat by P.J. Smit del et. lith. in 'Christmas Island (Indian Ocean): physical features and geology; with descriptions of the fauna and flora by numerous contributors.' by Charles William Andrews (1900). This image is in the public domain because its copyright has expired. This applies to the European Union, Canada, the United States and those countries with a copyright term of life of the author plus 70 years.

Mus nativitatis Thomas, 1888

According to Thomas (1888), the Bulldog Rat's (Rattus nativitatis) morphology distanced it from other described species of Rattus. This species was listed as the only member of the "nativitatis" group in the subgenus Rattus (Ellerman, 1941), but that placed in the same group with the Maclear's Rat (Rattus macleari) within the subgenus Stenomys (Ellerman, 1949). Chasen (1940) thought that the Bulldog Rat had no close relatives in Malaysia. However, Misonne (1969) placed this species in the subgenusp Leooldamys, close to the Rajah Spiny Rat (Rattus rajah = Maxomys rajah). This was later rejected by Musser (1981) and Musser and Newcomb (1983). According to Wilson and Reeder (2005), four hypotheses about the Bulldog Rat's phylogenetic position require testing: 1) it is most closely related to Rattus macleari, the other endemic on Christmas Island; 2) it is not related to Rattus macleari but to other species of Rattus; 3) it is a member of Rattus but phylogenetically isolated from all other species; 4) it is not even a member of Rattus.(Wilson and Reeder, 2005)

The Ross family in Christmas Island have given this species the name "Bull-dog Rat," and this has been adopted by the Malays (Andrews, 1900; Day, 1981).

The Bulldog Rat was a large rat that had a head and body length of about 25-27 cm (Andrews, 1900). This rat's head was peculiarly small, slender and delicate (Andrews, 1900; Day, 1981). Its dorsal fur had long, thick and course hair and its fur was coloured dark umber-brown or reddish brown all over, the belly was not or scarcely lighter than the back (Andrews, 1900; Aplin 2008). Some individuals were much warmer brown than others, a difference that occurs irrespective of sex and in some individuals there is a small irregular patch of white fur on the belly (Andrews, 1900). The fur of very young Bulldog Rats is coloured bluish black (Andrews, 1900). This species' very thick tail has a length of about 17 cm, which is proportionately short and made it easily distinguishable from the longer tailed Maclear's Rat (Andrews, 1900; Flannery, 1990). The nearly or quite naked tail was coloured uniform blackish brown, however the white skin was showing to a certain extent between the 'scales' (Andrews, 1900). Its weight is estimated at 250-300 gram (Department of the Environment, Water, Heritage and the Arts, 2009). On the upper surface of the body it had a up to 2 cm thick layer of subcutaneous fat (Flannery, 1990). The Bulldog Rat had strong, broad claws (Day, 1981). The hand and feet were very thick and heavy; the claws, especially on the fore feet, were enormously broad and strong (Andrews, 1900). The palms and soles were naked and smooth and the last hind foot pad was elongated (Andrews, 1900).

Images: The skull of a Bulldog Rat in 'Christmas Island (Indian Ocean): physical features and geology; with descriptions of the fauna and flora by numerous contributors.' by Charles William Andrews (1900).These images are in the public domain because its copyright has expired. This applies to the European Union, Canada, the United States and those countries with a copyright term of life of the author plus 70 years.

Table 1: Measurements by O. Thomas (1888) and C.W. Andrews (1900)

The Bulldog Rat's diet has never been recorded (Department of the Environment, Water, Heritage and the Arts, 2009). This species' diet probably consisted of wild fruits, young shoots, and the bark of some trees (Andrews, 1900).

The Bulldog Rat is strictly nocturnal (Andrews, 1900; Tidemann, 1989; Day, 1981), and when exposed to bright daylight it seems to be in a half-dazed condition (Andrews, 1900;Flannery and Schouten, 2001). Its short tail and robust hands and feet demonstrate that it was equipped for life as a fossorial species (Andrews, 1900; Thomas, 1888; Forsyth Major, 1900; Lamoreux, 2008b), meaning it was adapted for digging (Day, 1981). This species is more sluggish than the Maclear's Rat (Rattus macleari), another recently extinct rat species from Christmas Island (Andrews, 1900; Day, 1981). Unlike the Maclear's Rat it did not climb trees (Andrews, 1900).

The Bulldog Rat was endemic to Christmas Island, Australia. This 135 km² large island lies 345 km south of Java (Indonesia) in the Indian Ocean. (Andrews, 1900; Lamoreux, 2008b; Wyatt et al. 2008) Bulldog Rats occurred on the higher hills and in the denser forests of Christmas Island (Flannery and Schouten, 2001;Department of the Environment, Water, Heritage and the Arts, 2009). According to Andrews (1900), "they seem to live in small colonies in burrows, often among the roots of a tree, and occasionally several may be found living in the long, hollow trunk of a fallen and half-decayed sago-palm (Arenga listeri)".

Image: map showing the location of Christmas Island, the former range of the Bulldog Rat Created by Peter Maas for The Sixth Extinction Website. This image has been released under the Creative Commons Attribution Non-commercial No Derivatives 3.0 Licence. This applies worldwide.

In the early seventeenth century, British and Dutch navigators first included the island on their charts. Captain William Mynors of the British East India Company vessel, the Royal Mary, named the island when he arrived on Christmas Day, 25 December 1643. The island first appears on a map produced by Pieter Goos and published in Holland in 1666, in which it is called Mony. (Andrews, 1900; Wikipedia contributors, 2009)

In 1886 the British surveying vessel, H.M.S. "Flying Fish" (Captain Maclear) was ordered to make an examination of the island. A number of men were landed, and collections of the plants and animals were obtained, but, since the island seemed of little value, no serious attempt at exploration was made. In1887 H.M.S. "Egeria" (Captain Pelluim Aldrich)called at the island, and remained about ten days. Captain Aldrich and his men cut a way to the top of the island, and sent home a number of rock specimens obtained on the way, and Mr. J. J. Lister, who accompanied the expedition as naturalist, made extensive collections both of the fauna and flora, but had not time to penetrate to the middle of the island. (Andrews, 1900)

The collections brought back by the officers of H.M.S. "Flying Fish" and by Mr. Lister included two species of rat (Rattus macleari and Rattus nativitatis), a large fruit-bat (Pteropus natalis), and a shrew (Crocidura trichura). All these species have been described by Mr. 0. Thomas in two papers dealing with the collections made by the officers of H.M.S. "Flying Fish" and by Mr. J. J. Lister. (Andrews, 1900)

At the time of the visit of H.M.S. Egeria, the island was found to be entirely uninhabited, and there was no indication that Christmas Island had ever been occupied. Captain Aldrich gathered a large biological and mineralogical collection. The discovery of commercially exploitable deposits of phosphate among Aldrich's collection led to annexation of the island by H.M.S. Impéreuse on 6 June 1888 and placed under the Straits Settlements Government by the British Crown. Soon afterwards, a small settlement was established in Flying Fish Cove by G. Clunies Ross, the owner of the Keeling Islands (some 900 kilometres to the south west) to collect timber and supplies for the growing industry on Cocos. (Andrews, 1900; Wyatt et al. 2008; Wikipedia contributors, 2009)

The endemic rats of Christmas Island, described as “abundant” when first collected in 1887 (Andrews, 1900;Thomas, 1887). The Bulldog Rat was last recorded with certainty by Andrews from his from his 10 month stay on Christmas Island 1897-1898 (Andrews, 1900; Lamoreux, 2008b). At that time, it already appeared to be in decline (Lamoreux, 2008). It is thought that the Black Rat (Rattus rattus) has been introduced in 1899 by the S.S. Hindustan (Pickering and Norris, 1996; Lamoreux, 2008b; Wyatt et al. 2008), eventually resulting in the disappearance of the Bulldog Rat.

Durham visited the island in November of 1901 to March 1902 and collected Maclear's Rats (Rattus macleari) and Black Rats (Rattus rattus), but was unable to obtain Bulldog Rats (Rattus nativitatis), despite offering a reward to the local inhabitants (Pickering and Norris, 1996; Lamoreux, 2008b). In 1904, K. R. Hanitsch who visited Christmas Island for five weeks hoping to collect specimens of the native rats, but was unable to locate either species (Pickering and Norris, 1996; Lamoreux, 2008b).

The extinction of the Bulldog Rat is thought to have been the result of an epidemic disease, or more likely a number of different diseases (Flannery 1990), introduced by the Black Rat that had been inadvertently brought to the island by sailors (Andrews 1909; Aplin 2008, Lamoreux, 2008b).  

A medical officer on the island, Dr. McDougal, recalled frequently seeing "individuals of the native species of rats crawling about the paths in the daytime, apparently in a dying condition" in 1902-1904. These rats were probably Maclear's Rats (Rattus macleari) because the Bulldog Rat (Rattus nativitatis) was the rarer of the two, as evidenced by the fact that Durham was unable to collect any specimens of the Bulldog Rat in 1901-1902. (Andrews, 1909, Day, 1981; Wyatt et al. 2008; Lamoreux, 2008a; Lamoreux, 2008b) One explanation proffered at the time by the pioneering tropical parasitologist H.E. Durham (Durham, 1908; Pickering and Norris, 1996) was that the animals were suffering from a highly infectious and fatal trypanosomiasis, perhaps carried by infected fleas on the Black Rat (Rattus rattus) (Day, 1981; Wyatt et al. 2008).

In 2008, DNA evidence from museum specimens of these rats showed that the endemic rats (Bulldog Rat and Maclears Rat) collected prior to the introduction of Black Rats did not yield trypanosome sequences. However, DNA from the murid trypanosome Trypanosoma lewisi has indeed been found in Maclear's Rat and Black Rat collected after the introduction of the Black Rat on Christmas Island. The introduction of Trypanosoma lewisi, to immunologically naïve endemic rats on Christmas Island around 1900 is consistent with contemporary reports of widespread morbidity and perhaps also extensive mortality that so reduced endemic populations that they collapsed to the point of complete extinction. This evidence represents, for mammals, the first verified correlation in time of novel pathogen introduction and species-level extinction. (Wyatt et al. 2008)

Image: Trypanosoma lewisi (adult form in rat blood), a parasite of rats (e.g. Rattus rattus) transmitted by fleas (Desquesnes et al. 2002). Photographed by Marc Desquesnes. This image was published in a BioMed Central journal. Their website states that the content its open access articles fall under the BioMed Central Copyright and License Agreement (identical to the Creative Commons Attribution 2.0 License).

Two invasive predators had been introduced to Christmas Island and became established by the early 1900s, but these were far too few to rid the island of the rats (Andrews 1900, 1909; Ridley, 1906; Lamoreux, 2008a) and there does not appear to be a direct link between these predators and the demise of the Bulldog Rat (Tidemann 1989; Department of the Environment, Water, Heritage and the Arts, 2009).

There are and were no conservation measures taken for the Bulldog Rat (Lamoreux, 2008). Under Australian Government legislation this species is listed as Extinct under the Environment Protection and Biodiversity Conservation Act 1999 (Department of the Environment, Water, Heritage and the Arts, 2009).

Two specimens were collected by Lister in 1887 (Thomas, 1888), and a further nine specimens were collected by Andrews in 1897-1898 (Andrews, 1900). (Lamoreux, 2008b) All of the few specimens known tot still exist, are housed at just three institutions from the United Kingdom: the Natural History Museum, London (NHML), and Museum of Zoology of Cambridge University (CMZ), and the Museum of Natural History of Oxford University (OMNH) (Wyatt et al. 2008).

The Bulldog Rat was one of the two endemic rat species on Christmas Island. The second species was the Maclear's Rat (Rattus macleari), which became extinct in 1904 (Lamoreux, 2008a).

Bulldog Rat - Wikipedia, the free encyclopedia

Andrews, C.W. (1900). Mammals. pp. 22–37 in Andrews, C.W. (ed.). A Monograph of Christmas Island (Indian Ocean): physical features and geology; with descriptions of the fauna and flora by numerous contributors. London : British Museum (Natural History) xiii 337 pp. Available online: http://www.archive.org/details/monographofchris00brit. 

Andrews, C.W. 1909. An account of Andrew's visit to Christmas Island in 1908. Proceedings of the Zoological Society of London 1909: 101–103

Aplin, K.P. (2008). Bulldog Rat, Rattus nativitatis. In: van Dyck, S. & R. Strahan, eds. The Mammals of Australia. Sydney: Reed New Holland.

Chasen, F. N. (1940). A handlist of Malaysian mammals: A systematic list of the mammals of the Malay Peninsula, Sumatra, Borneo, and Java, including the adjacent small islands. Bulletin of the Raffles Museum, Singapore, 15:1-209.

Day, D., 1981, The Doomsday Book of Animals, Ebury Press, London.

Department of the Environment, Water, Heritage and the Arts (2009). Rattus nativitatis in Species Profile and Threats Database, Department of the Environment, Water, Heritage and the Arts, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed 2009-10-03@07:20:49.

Desquesnes, M., S. Ravel and G. Cuny. (2002). PCR identification of Trypanosoma lewisi, a common parasite of laboratory rats. Kinetoplastid Biology and Disease 1: 2.doi:10.1186/1475-9292-1-2. http://archive.biomedcentral.com/1475-9292/1/2 

Durham H.E. (1908). Notes on Nagana and on some Haematozoa observed during my travels. Parasitology 1: 227–35.

Ellerman, J. R. (1941). The families and genera of living rodents. Vol. II. Family Muridae. British Museum (Natural History), London, 690 pp.

Ellerman, J. R. (1949). The families and genera of living rodents. Vol. III, Appendix II [Notes on the rodents from Madagascar in the British Museum, and on a collection from the island obtained by Mr. C. S. Webb]. British Museum (Natural History), London, 210 pp.

Flannery, T. (1990). The rats of Christmas past. Australian Natural History. 23(5):394-400.

Flannery, T. & P. Schouten (2001). Een gat in de natuur. Amsterdam/Antwerpen: Uitgeverij Atlas. [The original English version: Flannery, T. & P. Schouten (2001). A Gap in Nature: Discovering the World's Extinct Animals. New York: Atlantic Monthly Press.]

Forsyth Major, C.I. 1900. Notes on the osteology of Mus nativitatis and Mus macleari. pp. 34-37 in A monograph of Christmas Island (Indian Ocean). British Museum of Natural History : London. 34–37 pp.

Lamoreux, J. (2008a). Rattus macleari. In: IUCN (2009). IUCN Red List of Threatened Species. Version 2009.1. <www.iucnredlist.org>. Downloaded on 03 October 2009.

Lamoreux, J. (2008b). Rattus nativitatis. In: IUCN (2009). IUCN Red List of Threatened Species. Version 2009.1. <www.iucnredlist.org>. Downloaded on 03 October 2009.

Misonne, X. (1969). African and Indo-Australian Muridae: Evolutionary trends. Annales Musée Royal de l'Afrique Centrale, Tervuren, Belgique, Serie IN-8, Sciences Zoologiques, 172:1-219.

Musser, G. G. (1981). Results of the Archbold Expeditions. No. 105. Notes on systematics of Indo-Malayan murid rodents, and descriptions of new genera and species from Ceylon, Sulawesi, and the Philippines. Bulletin of the American Museum of Natural History, 168:225-334.

Musser, G. G., and C. Newcomb. (1983). Malaysian murids and the giant rat of Sumatra. Bulletin of the American Museum of Natural History, 174:327-598.

Pickering J, Norris CA (1996) New evidence on the extinction of the endemic murid Rattus macleari from Christmas Island, Indian Ocean. Australian Mammalogy 19: 35–41.

Ridley, H.N. (1906). An expedition to Christmas Island. Journal of the Straits Branch of the Royal Asiatic Society. 45:137.

Thomas, O. (1887) Report on a zoological collection made by the officers of H.M. “Flying Fish” at Christmas Island, Indian Ocean. I. Mammalia. Proceedings of the Zoological Society of London 1887: 511–514.

Thomas, O. (1888) [1889]. On the mammals of Christmas Island. Proceedings of the Zoological Society of London, 1888:532-534.

Tidemann, C. (1989). Survey of the terrestrial mammals on Christmas Island (Indian Ocean). Forestry Department, Australian National University.

Wikipedia contributors (2009), "Christmas Island," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Christmas_Island&oldid=317536758(accessed October 3, 2009).

Wilson D.E. & DeeAnn M. Reeder (editors). (2005). Mammal Species of the World. A Taxonomic and Geographic Reference (3rd ed), Johns Hopkins University Press, 2,142 pp. Available online: http://www.bucknell.edu/MSW3/.

Wyatt K.B., Campos P.F., Gilbert M.T.P., Kolokotronis S-O., Hynes W.H., et al. (2008) Historical Mammal Extinction on Christmas Island (Indian Ocean) Correlates with Introduced Infectious Disease. PLoS ONE 3(11): e3602. doi:10.1371/journal.pone.0003602.