Article

Rodentia

From Munshipedia, the MBRAS digital historical encyclopedia

Rodentia

Rodentia, the order of rodents, has been a subject of sustained zoological investigation across the Malay Peninsula and Borneo since the late nineteenth century, encompassing work that ranges from single-specimen taxonomic notes to broad epidemiological surveys of plague vectors. The order’s significance in the region is twofold: ecologically, it includes species of considerable altitudinal and geographic diversity, from lowland house rats to highland forms found above a thousand metres; and practically, several species have been identified as vectors of bubonic plague, making their accurate identification a matter of public health concern. The literature preserved in the Society’s journals reflects both dimensions, with early contributions focused on range extensions and nomenclatural clarification, and later work increasingly oriented toward the applied question of which species matter for sanitary control [1], [2].

Taxonomic Scope and Nomenclatural Revision

The earliest contribution in the present corpus is a brief note by A. L. Butler recording the first confirmed occurrence of Mus surifer, G. S. Miller, in Perak [1]. Butler drew attention to Miller’s 1900 description of seven new rat species from the mountains of Trong, Siam, and noted that M. surifer was recorded from the Larut Hills, Perak, adding that at least some of the other new species probably follow the main range down the Peninsula [1]. His own field experience illustrates the difficulty of securing such specimens: he first trapped an individual near the Hut on Maxwell’s Hill in February 1898, only to lose it to a small carnivore, and then successfully trapped a live specimen the following year, which he kept briefly before it escaped in Kuala Lumpur [1]. A damaged specimen obtained from coolies was sent in spirit to Oldfield Thomas, who confirmed its identity as M. surifer [1].

By the 1920s, the taxonomic work had shifted from single-specimen confirmations to systematic revision of entire faunal assemblages. Chasen and Kloss (1928), working on material collected by H. C. Siebers during the 1925 Middle-East Borneo Expedition, addressed a gap in mammalian knowledge of Eastern Borneo, a region previously worked only sporadically by Lumholtz (1914–1915) on the Boelongan River and Abbott (1908–1909) south of Balik Papan Bay [3]. Although Siebers was primarily an ornithologist, his mammal collection proved taxonomically productive, yielding material from the Telen River drainage in the Samarinda division, extending from Tenggarong at sea level to Punt D at 1,172 metres, supplemented by a few specimens from the Melawi River in Western Borneo [3].

A significant portion of Chasen and Kloss’s paper is devoted to resolving nomenclatural confusion. For the palm civet, they argued against recognising two size-based races (sabanus and baritensis) in Borneo, contending that Viverrids show too much individual variation in size for dimensional subspecies to be reliably proposed on small samples [3, p. 39]. Similarly, for the short-tailed mongoose, they rejected Thomas’s distinction between a lowland rajah and a mountain dyacorum, attributing the rufous appearance of old dyacorum skins to deterioration rather than genuine colour difference, and adopted rajah as the prior name for all Bornean forms [3, p. 40]. Although these concerns fall outside the strict boundaries of Rodentia, they establish the methodological framework within which the rodent determinations were made.

Bornean Rodent Fauna and Altitudinal Variation

The rodent section of Chasen and Kloss’s paper is the most extensive, covering squirrels, rats, and a shrew-mouse [3]. Among squirrels, the authors noted that Sciurus notatus dilitensis from the east of Borneo is consistently paler below than western specimens, and that Sciurus tenuis jentinki represents a distinct altitudinal form occurring at 1,172 metres at Long Petak [3, p. 42]. This record represents the highest altitude yet documented for this altitudinal form, which co-occurs with S. brookei at the same locality [3, p. 42].

Among rats, Chasen and Kloss confirmed Rattus surifer bandahara from Kina Balu in the Telen drainage and identified Rattus argentiventer from a single specimen at Moeara Antjaloeng [3, p. 47]. The latter identification was made despite a damaged skull, relying on diagnostic cranial features: a longer toothrow, larger bullae, and a broader infraorbital plate, which distinguish it from the rattus group [3, p. 47]. In the flesh, the specimen measured 174 mm in tail length against 157 mm in head and body length, with a hindfoot of 34 mm [3, p. 47].

The authors also described two new subspecies of pygmy squirrel: Nannosciurus melanotus pallidus (type: adult male, Long Poehoes, 10 August 1925, Buitenzorg Museum No. 1178; condylo-basilar length 21 mm) and N. exilis sordidus (type: adult female, Long Temelan, 26 August 1925, Buitenzorg Museum No. 1189; condylo-basilar length 19 mm), both distinguished from their western counterparts by duller, greyer upperparts and reduced rufous suffusion [3, pp. 43–44]. In a related taxonomic move, they rejected Nannosciurus exilis as a Sumatran species, reassigning the type locality to the Kapuas River basin in Western Borneo on the grounds that no reliable record exists from Sumatra and the species’ presence in the Sulu and Philippine groups makes a southwestern Malaysian origin improbable [3, p. 44].

A single Chiropodomys specimen from Long Petak was noted as distinct from all described Bornean forms in having fawn-coloured underparts rather than white, but no new name was proposed given the single example [3, p. 48]. The insectivore section records a range extension of Tupaia glis salatana northward to the Melawi River, beyond its previously known range along the south coast from Pangkallahan to Kendawangen [3, p. 48].

Plague Vectors and Applied Zoology

The most extensive treatment of rodents in the corpus is C. B. Kloss’s 1911 review, “Rats and plague,” which assessed the zoological foundations of Indian plague research and applied its findings to the rat fauna of the Malay Peninsula [2]. Kloss, a naturalist working in the Straits Settlements, argued that while Indian plague commissions had correctly identified the epidemiological importance of rats, their taxonomic work was riddled with errors stemming from overreliance on outdated classifications and confusion between normal variation and distinct species—errors that would mislead any Malayan sanitary officer attempting to replicate the investigations locally [2].

Kloss reviewed two major Indian publications: Dr. W. C. Hossack’s illustrated account of Calcutta’s plague rats and Surgeon-Captain R. E. Lloyd’s “The Races of Indian Rats.” Both works, while valuable in their epidemiological observations, were faulted for resting on Oldfield Thomas’s 1881 monograph on the genus Mus without acknowledging the substantial taxonomic revisions that had accumulated over the intervening three decades [2]. Lloyd in particular was criticised for mistaking colour “sports” (abnormal variants) of Mus rattus for distinct species, and for failing to recognise that the non-rattus rats with bicoloured tails and spiny coats are rural animals never found in towns—a basic ecological fact that, had it been grasped, would have prevented much of the confusion in his species determinations [2, pp. 159–161].

The article then pivots to the practical question of which rat species matter for plague control in the Malay Peninsula. Kloss identified the principal vectors as Mus decumanus (the ship rat, confined to major ports), Mus griseiventer (the common house rat of the southern Peninsula), Mus concolor (a small, spiny-coated form of Mus rattus found in both town and country), and the bandicoot-rats Gonomys varius and G. varillus (introduced species, probably carried in rice-ships from Burma) [2, pp. 163–166]. He provided detailed morphological keys—pelage texture, tail colouration, skull architecture, molar structure, and a previously unnoted feature of the jaw bone—to enable field identification by sanitary officers who may lack zoological training [2, pp. 163–166].

A comparative analysis of species proportions drawn from Indian and Burmese plague investigations revealed striking regional differences. In Calcutta’s northern native quarter, Nesokia bengalensis and Mus decumanus were caught in ratios of 60 and 26 per cent respectively; in the central European quarter these were reversed to 37 and 51 per cent, while Mus rattus formed only 15 per cent of the total [2, p. 159]. In Rangoon, by contrast, Mus rattus plus Mus concolor constituted 72 per cent of plague-related rat specimens, Gonomys species 21 per cent, and Mus decumanus only 7 per cent—sharply contrasting with Indian proportions [2, p. 162]. Kloss noted that Mus concolor formed at least 50 per cent of Rangoon’s total rat catch and at least 75 per cent of its true house rats, and had not been recorded from India [2, p. 161]. He suggested that the Malayan situation, closer to the Burmese pattern, would present a different epidemiological profile from that of India [2, pp. 161–162].

Gonomys varius and G. bengalensis overlapped in Rangoon in a ratio of three to two; G. varillus was recently taken in large numbers there and had probably been carried to Penang in rice-ships [2, pp. 162–163]. Mus decumanus was described as one of the most dangerous plague species owing to the large number of parasites it harbours, and was confined in Malaya to the major ports of Singapore, Penang, Malacca, and Port Swettenham, with a few individuals recorded from Johore Bahru [2, p. 163]. The rat-flea Pulex cheopis was identified as the sole known disseminator of plague, making rat destruction the simplest method of eliminating the flea vector [2, p. 163].

Research and Documentation

The Society’s literature on Rodentia reveals a clear trajectory from descriptive natural history toward applied taxonomy. Butler’s 1901 note represents the earliest phase: a single-specimen confirmation, dependent on the authority of Oldfield Thomas for final identification, and framed by the broader question of how far Miller’s Siamese species extend down the Peninsula [1]. Kloss’s 1911 review marks a decisive shift in purpose: the rodent is no longer an object of curiosity but a public health concern, and the taxonomic work is explicitly subordinated to the needs of sanitary officers in the field [2]. Kloss’s distinctive contribution lies in his dual role as practising naturalist and critic of the Indian plague literature; his article is as much a taxonomic correction as an epidemiological review, written to equip colonial sanitary officers with the zoological literacy the Indian reports had lacked [2].

Chasen and Kloss’s 1928 paper represents the most systematic treatment in the corpus, combining range extension, altitudinal documentation, and nomenclatural revision within a single framework [3]. The work sits within the broader programme of the Indisch Comite voor Wetenschappelijke Onderzoekingen, whose 1925 Middle-East Borneo Expedition was published in 1927, and represents one of the first systematic mammalogical treatments of the Mahakam–Telen drainage system [3]. The primary material derives from the Buitenzorg (now Bogor) Zoological Museum collection, with determinations made at the Raffles Museum, Singapore; the authors also consulted comparative series from Sarawak and the Malay Peninsula held in their own collections [3].

Across the three contributions, a consistent methodological concern emerges: the difficulty of distinguishing genuine taxonomic entities from individual variation, colour aberrations, or artefacts of preservation. Butler’s reliance on a single confirmed specimen, Kloss’s critique of Lloyd’s species determinations, and Chasen and Kloss’s rejection of size-based subspecies in Viverrids all reflect the same underlying problem—how to draw reliable boundaries in a fauna that is still being mapped, often from small and imperfect samples [1], [3], [2].

MBRAS Sources

References

  1. A.L. Butler (1901). On the occurrence of Mus surifer, G.S. Miller, in Perak JSBRAS 36: 137.
  2. C.B. Kloss (1911). Rats and plague JSBRAS 57: 157–166. Read on JSTOR
  3. F.N. Chasen and C.B. Kloss (1928). On some Carnivora, Rodentia and Insectivora principally from Eastern Borneo JMBRAS 6(1): 38–49. Read on JSTOR