Bornean Rainbow Toad
Rediscovery of one of the world’s top 10 most wanted “lost” frogs, Ansonia latidisca, the Bornean Rainbow Toad, on Gunung Penrissen, Western Sarawak, Borneo Ansonia latidisca, is an endangered species of tropical bufonid (Inger et al. 2004), currently known from two locations in the northwestern corner of Borneo. Prior to our discovery, this species was known from only three individuals. The holotype, an adult male, was collected by Johann Gottfried Hallier (1868–1932), a botanical assistant at the Buitenzorg (at present Bogor) Herbarium, from the summit of Gunung Damus (Kalimantan, Indonesia), the paratype, a female, taken by Robert Walter Campbell Shelford (1872–1912), entomologist with the Sarawak Museum, from Gunung Penrissen (Sarawak, Malaysia), in addition to a third specimen from the latter locality, collected by Eric Georg Mjöberg (1882–1938), Curator of the Sarawak Museum. Listed as one of the ‘World’s Top 10 Most Wanted Lost Frogs’ by the IUCN SSC Global Amphibian Specialist Group and Conservation International, A. latidisca has not been sighted since the late 1920s (see Inger 1966; Inger et al. 2004). The only published literature is the original description of Inger (1966), who referred to it as a montane species, with the holotype collected at about 1,200 m asl and the paratype at 1,300 m asl. The species is considered valid (see Manthey and Grossmann 1997; Matsui et al. 2009), and is listed as Endangered in Stuart et al. (2008) “in view of its extent of occurrence of less than 5,000 km2 and area of occupancy of less than 500 km2, with all individuals in fewer than five locations, and a continuing decline in the extent and quality of its habitat”.
The 1,329 m Gunung Penrissen (Fig. 1) dominates western Sarawak, and forms the boundary between Malaysia’s Sarawak State and Indonesia’s Kalimantan Barat Province, and is drained mainly by Sungei Semadang and the headwaters of the Batang Kayan. The geology of this sandstone massif has been investigated by Wilford and Kho (1965), and comprises a matrix of sandstone and karst features, rising to the rugged ridges of the Penrissen range. The first and till now only multitaxic biotic inventory was conducted by Robert Shelford, on behalf of the Sarawak Museum, starting 5 May 1899 (described in Shelford 1916). Although Shelford’s own interest was entomology (see Shelford 1901b), significant herpetological material was collected, which formed the basis of a couple of papers (Shelford 1901a; 1905), and others appear in list of material examined (e.g., Smith 1925; Inger 1966). Early collections of Shelford and his successors continue to form the mainstay in terms of material for research on various taxonomic groups of plants and animals of Gunung Penrissen.
Figure 1. View of summit of Gunung Penrissen, Sarawak, type locality of Ansonia latidisca.
Penrissen lies outside the protected area system of Sarawak, but is listed among the Important Bird Areas of the world by BirdLife International (www.birdlife.org). Threats to the area include resort development, poaching and habitat fragmentation (Anon. 2010a). The area has a long history of agriculture, especially rice, although rubber and pepper are also grown in all except the steepest terrain. Extraction of metallic and non-metallic minerals may also comprise a threat to the landscape in the future. Major development projects commenced in the Gunung Penrissen area in the last decade, with the view of promoting ecotourism and golf-tourism, the environmental effects of which remain largely unstudied. The 2,071 hectare resort, now operational close to the summit (at ca. 1,000 m asl), was planned by a Hawaii-based consortium (Tongg Clarke & McCelvey), and included an ambitious plan of development, including removal of most of the native vegetation, which was replaced largely with an 18-hole golf course and a 25 acre area of ‘flower garden and theme parks’ (Anon. 2010b). Baseline information on Penrissen’s biodiversity is, however, meagre, the existing information stemming from Shelford’s collection based on a single visit to these mountains (described in Shelford 1899).
We have initiated field work on Gunung Penrissen since August 2010, in a project initiated by The Search for Lost Frogs campaign, to discover populations of Ansonia latidisca, employing standard inventory techniques appropriate for forest-dwelling bufonids. We have located three individuals of A. latidisca on three different mature trees (ca. 2 m above ground) near forest trails (Figs 2–3). Prior to this, no photograph of live A. latidisca was available.
Figure 3. Head in lateral view of adult female Ansonia latidisca.
Of the three A. latidisca encountered, OJJ-0009 is a juvenile, measuring 30.14 mm in snout-vent length (SVL). OJJ-0010 and OJJ-0011 are male (SVL 42.6 mm) and female (SVL 51.8 mm), respectively. The single male found show a distinctive vocal sac and developed testes. The female carries unripe ova, suggestive of reproduction later in the year. The description by Inger (1966) of A. latidisca match our specimens, with the male being smaller with a vocal sac and nuptial pads not visible. Our sample agrees further with the original description in showing large body size (in the female), exposed tympanum, dilated finger tips, elongate limbs and lack of tarsal fold. We consequently announce the rediscovery of Ansonia latidisca after its last collection in 1924.
In a recently published molecular phylogeny of the genus Ansonia (see Matsui et al. 2010), we did not include A. latidisca for lack of genetic material. However, an examination of its morphology indicates that the relation of this taxon may ultimately lie with another group of bufonids (including the bright dorsal pigmentation, elongate limbs, spatulate digit tips, and arboreal habits). Another Bornean bufonid, Ansonia anotis Inger, Tan, and Yambun 2001 and Pedostibes maculatus (Mocquard 1890), have been shown to be the same biological species, and has been allocated to a new genus- Sabahphrynus Matsui et al. (2007). Ansonia latidisca shares may characters with this taxon, differing in showing a tympanic annulus. Thus warrant further systematic work, including reevaluation of both its generic assignment (Ansonia) and consequently, of its suggested common English name (“stream toad”).
Prior to the establishment of the Borneo Highlands Hornbill Golf & Jungle Club in 2000, the low and mid-elevation of Gunung Penrissen was extensively logged, restricting intact vegetation largely to the upper montane habitats. Although these forests have since been maintained as a reserve and as catchment area, habitat fragmentation may threaten the long-term survival of A. latidisca. The species is listed as Endangered in the IUCN Red List (see Inger et al. 2004), but is not protected under the Sarawak Wildlife Ordinance 1998. We refrain from divulging the exact site of observation, owing to the intense demand for brightly-coloured amphibians by collectors who supply the pet trade, locally and internationally (see Stuart et al. 2006 for justification).
Funding support for field research came from The Search for Lost Frogs campaign of Conservation International, in partnership with the IUCN SSC Amphibian Specialist Group and the Global Wildlife Conservation, as well as a grant from Shell Chair (SRC/05/2010), administered by the Institute of Biodiversity and Environmental Conservation, Universiti Malaysia Sarawak. We are grateful to Robin Moore, Don Church, and Nicolette Roach for support. For institutional support, we thank the Institute of Biodiversity and Environmental Conservation, Universiti Malaysia Sarawak, and our Director, Andrew Alek Tuen. Bernard Tiang, Cynthia Baring-Gould and Ramona Ngalih, of the Borneo Highlands Hornbill Golf & Jungle Club, provided us logistic support. We also thank David J. Gower for images and data associated with the long-preserved BMNH specimens of “Ansonia” latidisca. Finally, we thank the Sarawak Forest Department and Sarawak Forestry Corporation for permission (no. NCCD.907.4.4(V)-202) to conduct research.
By Pui Yong Min, Ong Jia Jet and Indraneil Das
For more information please contact Indraneil Das: firstname.lastname@example.org. This article was originally published in FrogLog 97.
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