Notes on the fauna of Pulau Bulan, Rhio Archipelago. Records of the Raffles Museum, No. 2
F. N. Chasen, a naturalist attached to the Raffles Museum, published this brief faunal account in 1924 following a ten-day collecting expedition to Pulau Bulan in the Rhio Archipelago in early April of that year. The paper describes three new subspecies of the striped squirrel (Sciurus vittatus) from the island and its neighbours, and provides a checklist of mammals and birds obtained or observed during the visit.
Summary
Chasen’s primary objective was mammal collection, but the animals proved so scarce that he supplemented the work with small collections of other taxa. The ecological context is striking: the entire island was leased by the Netherlands India Government to a rubber company, and by 1924 the landscape had been so transformed by plantation agriculture that Chasen found it “difficult to imagine a more depressing place from a naturalist’s point of view” (p. 59). Only a small remnant of timber remained on the northern slopes of Bulan Peak (approximately 800 ft.), and the western coast jungle could not be visited within the time available.
The taxonomic core of the paper is the description of three new squirrel subspecies: S. v. lighti from Penang Island (type collected 1911), S. v. stellaris from Bintang Island (type collected 1908), and S. v. lunaris from Pulau Bulan itself (type collected by Chasen on 3 April 1924). Chasen frames these as examples of insular degradation, noting that the progressive weakening of the dark lateral stripe by the colour of the underparts represents “the first step towards their disappearance” (p. 58). The mammal list includes the crab-eating macaque, the banded langur (observed but not collected), the small mouse-deer (Tragulus javanicus stanleyanus), the warty pig (Sus cristatus andersoni), and several rats and bats. The bird list, by contrast, is described as unremarkable, representing “mostly the common lowland fauna of the Malay Peninsula and Sumatra” (p. 60).
The paper also incorporates records of specimens previously sent to the museum by Mr. and Mrs. de Burgh Thomas, who resided on the island, and references earlier visits by Dr. W. L. Abbott (1907) and H. C. Robinson and E. Seimund (1908).
Key Findings
- Three new subspecies of Sciurus vittatus described: lighti (Penang, 9 specimens examined), stellaris (Bintang Island, 5 specimens), and lunaris (Pulau Bulan, 7 specimens) (pp. 58–59).
- The warty pig (Sus cristatus andersoni) is described as “very plentiful” on the island, while the large Sus barbatus is confirmed absent (p. 60).
- Scotophilus castaneus is recorded for the first time from the Rhio Archipelago, with three specimens (2♂, 1♀) taken from a roost on the underside of a coconut-palm leaf (p. 61).
- The tiger, though recorded from neighbouring Bintang Island, has never been known to visit Bulan despite the abundance of pigs (p. 60).
- The Java sparrow (Munia oryzivora) had established itself on the island, though the single specimen shot showed “unmistakable signs of having been kept in captivity” (p. 60).
- A straight channel cut through the mangrove at the northern end of the island, known locally as “Selat Acheh,” is attributed to pirate activity, and small cannon of rough workmanship have been found on the island (p. 59).
Conclusion
Chasen’s definitive takeaway is that Pulau Bulan’s fauna, while taxonomically productive in yielding new squirrel subspecies, was already severely diminished by 1924 due to plantation conversion, and the insular squirrel forms represent a clear case of evolutionary degradation in isolated populations.
Context
- Chasen was a staff naturalist at the Raffles Museum (Singapore); the expedition was conducted on the museum’s behalf, and the paper was published as Record No. 2 of that institution.
- The island was under Dutch colonial administration (leased to a rubber company by the Netherlands India Government), placing this work within the broader context of early-twentieth-century colonial natural history in the Strait Settlements and the Dutch East Indies.