On a collection of mammals from the Anamba Islands, South China Sea
F. N. Chasen and C. Boden Kloss published this account in 1928 of a mammal collection made by Chasen on the Anamba Islands in the South China Sea during August–October 1925. The paper documents twelve new forms for the island group—four of them new subspecies—and establishes that the Anamba mammalian fauna is more closely allied to the Malay Peninsula than to the nearby Natuna Islands.
Summary
The Anamba Islands had previously been known mammalogically only through a single collection made by Dr. W. L. Abbott and C. B. Kloss in 1899–1900, which Gerrit S. Miller reported on in 1900. That earlier work yielded thirteen new forms and established a fauna of sixteen species (eighteen forms when intraspecific variation on three islands is counted). Chasen’s 1925 expedition to Pulau Siantan and Pulau Jimaja was designed in part to recover topotypes from Miller’s original series, and succeeded in obtaining topotypes for nine of the thirteen previously described races. The collection added twelve further forms, bringing the total known mammalian fauna of the group to thirty.
The paper is structured as a species-by-species account, with each entry providing locality data, specimen counts, external and cranial measurements, and taxonomic commentary comparing the Anamba forms with their nearest mainland or island relatives. Four new subspecies are formally described: Tragulus kanchil siantanicus and T. k. anambensis (the first actual specimens of Tragulus obtained from the group), Sciurus tenuis siantanicus, and Rattus validus terempa. Seven genera—Rhinosciurus, Pachyura, Galeopterus, Pteropus, Cynopterus, Miniopterus, and Hipposideros—are recorded from the Anambas for the first time, substantially broadening the known composition of the island’s fauna.
A recurring theme is the degree of isolation evident in the fauna. While the overall affinities point to the Malay Peninsula, the authors note that indigenous mammals are “only rarely inseparable from those of the mainland,” with several forms showing subtle but consistent cranial or colour differences from their nearest continental counterparts. The paper also addresses taxonomic questions left open by Miller, such as whether Rattus rattus sianticus is truly distinct from jalorensis of the Malay Peninsula, and whether Macaca irus pumilus warrants retention as a separate race.
Key Findings
- The 1925 collection added twelve forms to the Anamba mammal list, raising the total from eighteen to thirty forms for the entire island group (p. 28).
- Four new subspecies were described: Tragulus kanchil siantanicus (type: adult male, Raffles Museum No. 2653, collected 22 September 1925), T. k. anambensis (type: adult female, Raffles Museum No. 2713, collected 10 October 1925), Sciurus tenuis siantanicus (type: adult male, Raffles Museum No. 2639, collected 21 September 1925), and Rattus validus terempa (type: adult male, Raffles Museum No. 2504, collected 31 August 1925) (pp. 31–37).
- Rattus rattus sianticus from the Anambas is significantly larger than jalorensis from the Malay Peninsula: head and body 169–191 mm versus 143–170 mm; tail 187–215 mm versus 161–179 mm; hind foot 34–37 mm versus 29–33 mm (p. 36).
- Pteropus vampyrus malaccensis from Siantan has forearms of 195–208 mm and skull lengths of 75–82 mm, clearly larger than natunae from the North Natuna Islands and Borneo (p. 39).
- Galeopterus variegatus natunae is recorded from Siantan with an adult female condylo-basal length of 69 mm, matching the Natuna type (67.6 mm) and confirming the species’ range extends southward to the Anambas (p. 39).
- Topotypes were recovered for nine of Miller’s thirteen originally described Anamba races; the two Rhinolophus bats and Rattus cremoriventer flaviventer (known only from Jimaja) were not obtained on this occasion (p. 28).
Conclusion
Chasen and Kloss conclude that the faunal affinities of the Anamba Islands lie with the Malay Peninsula rather than the Natuna Islands, a pattern consistent with the group’s geographic position. The isolation of the archipelago has produced a fauna in which several resident forms are subtly but consistently differentiated from their mainland counterparts, though none are so distinct as to warrant specific rank. The paper effectively doubles the known mammalian diversity of the Anambas and provides the taxonomic baseline against which all subsequent work on the group’s vertebrate fauna would be measured.
Context
- Specimens are deposited in the Raffles Museum (now the National Museum of Singapore), with catalogue numbers assigned throughout; the paper draws on comparisons with material from the same collection and with published measurements from Miller’s 1900 type series.
- The work represents a significant contribution to the biogeography of the South China Sea island chains, building directly on Miller’s 1900 monograph and Lyon’s 1913 account of the Tupaiidae, and establishing the Anamba Islands as a distinct faunal unit with peninsular rather than Bornean affinities.