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AN INITIAL BIODIVERSITY ASSESSMENT OF KABAENA ISLAND

INTRODUCTION

Kabaeana Island lies 56km to the west of Buton Island in SE Sulawesi.  The island is more mountainous than Buton and has the 1500m Gunung Sambopolulu as the centre-piece of the island. It also boasts a large limestone crag, Batusangia, 1000m, which adds to the impressive vista, and the island is home to many cave systems.  The geology is different to that of Buton with large areas of ultra basic rock.

Most importantly from the biological perspective, there have been virtually no surveys of the wildlife of this substantial island.  In 1999 an Operation Wallacea bird survey team visited the island for 2 weeks.  This initial survey revealed the presence of a species of ground thrush (Zoothera sp.) that appeared markedly different from previously described species.  In 2002 an Operation Wallacea bird survey team returned to Kabaena to mist net the ground thrush and make detailed drawings, take photographs and make recordings of the calls for comparison with the ground thrush species on Buton and the mainland of Sulawesi.  This work appeared to confirm that the Zoothera species on Kabaena may be new to science.

Birds are the best studied taxonomic group worldwide and if a species new to science could be found on Kabaena Island, then the possibility for the discovery of new species in other groups was very high indeed.  Moreover, the earlier visits by the Operation Wallacea survey teams had shown that much of the island was already de-forested and the remaining areas appeared to be under threat.  There are no protected forest areas on Kabaena island, yet if the early indications from the bird work proved to be correct, then the island may contain a number of unique species.

The objectives of the 2001 survey therefore were to undertake rapid assessments on a range of other taxonomic groups in addition to birds and to identify the best remaiining areas of forest on the island which may contain these unique species.

In September 2001 the following scientists participated in the survey;

Dr Boeadi, Institute of Environmental Sciences (project leader and taxonomy of mammal species)

Dr Graeme Gillespie, Arthur Rylah Institute, Melbourne (herpetofauna surveys)

Dr Tigga Kingston, Boston University (bat surveys)

Dr Dave Kelly, Trinity College Dublin & Julia Robinson-Dean, RSPB (birds)

Dr Dave Bird, University of West of England (fish)

Andy Jennings, Durham University & Nicola Grimwood, Manchester Metropolitan University (small mammal surveys)

Graeme Cooper & Phil Stanier, Operation Wallacea (macaques)

In addition Evette Stevens and Mike Hawkins, University of Birmingham completed final year Honours dissertations on aspects of the macaque survey.

This year’s base camp was in the village of Enano, a very hospitable and culturally active village, with satellite camps in Tangkeno, Pongkalero, Dongkala and Rahadopi and far reaching flying camps in Batusangia, Gunnung Sambopululu, and in the forests downstream from Tangkeno. With up to 60 volunteers and staff present on the island at any one time, in up to four different locations, logistics were complex. Two ports serve the island, Sikeli on the west, and Dongkala on the east with a single road connecting them. Enano is slightly nearer Dongkala than Sikeli, and most movements, people and supplies from Bau Bau used this port, however the local market in Sikeli was more appropriate for local supplies of fresh fish and vegetables. There is also a driveable road from Sikeli to Tangkeno which was used for moving equipment and supplies; people tended to walk the old road, now a wide trail, direct from Enano, 2hrs as opposed to the 2.5hr drive, as it was much more comfortable. Kabaena’s road is more of a dirt track than a road, so two 4x4s with experienced drivers/mechanics were shipped from Bau Bau for the length of the expedition; an additional vehicle was hired when necessary. Accomodation in Enano, and other satellite camps was in local houses, as agreed by the Kepala Desa (head man), and all flying camps were simple hammock and tent arrangements.

We were there in late August, September, Kabaena’s dry season with an average daily temperature of 35 degrees in the shade, so most work survey work was done in early morning and late afternoon, though general trekking, caving and waterfall/river activities took place throughout the day. Due to our experience of the local porter availability during the recce in 2000, we brought some key local staff from Buton who not only had experience of working with the scientists, but had logistical awareness of what was required in expedition circumstances. Local porters were hired in addition when necessary, and the balance created by this was a good one; but for future reference, local "guides" often know less about the lay of the land than a well armed volunteer with a compass, map and GPS!

Medical facilities on the island are concentrated in Teomokole, near Sikeli, where there is a good clinic and supportive staff, and in Dongkala with a smaller clinic. Any expedition that comes here in the future should come medically prepared, with at least two medics on site at all times.

Radio communications with Bau Bau were conducted on SSB radios, and all satellite and flying camps were linked to Enano by VHF, the exception being Pongkalero where it was necessary to set up an additional SSB due to the distance between Pongkalero and Enano (20km). A radio operator is essential, as this is a remote island with no pre existing systems.

GEOLOGY

Kabaena is, geologically speaking, one of the least well known of the medium-sized Indonesian islands. No detailed geological map has been published, although the island appears on the 1:1,000,000 Ujung Pandang sheet (Sukamto et al.), which shows it to consist of two belts of ophiolitic rocks, in the north and south, separated by an east-west trending belt of metamorphic rocks exposed in an irregular strip of lower ground that cuts across the island from Sikeli to Tolitoli. Work during the 2001 visit was confined to the ‘lateral valley’ and the adjacent higher ground, utilising Enano as the base of operations. The outcrop pattern shown on the published map was confirmed and explained. It seems that the ophiolite rests on a sub-horizontal thrust sheet which is generally a few tens to a few hundreds of metres above sea level. Outcrops in the lower ground, and hence below this thrust, are of metamorphic rocks which become more deformed as the thrust plane is approached. Outcrops at higher levels, in the cental mountain range, are of ophiolitic rocks. It is assumed that the same is true of the northern hills, although these were not visited. In the vicinity of Enano, the ophiolitic rocks are dominantly gabbros.

The lateral valley was evidently below sea level in the not too distant past, since coral reef knolls west of Enano now rise to heights of over 100 m above the plain. These are assumed to be Quaternary, although no dates have been reported. Near Sikeli, on the west coast, there is an area of low rounded hills which support only a poor grassland vegetation. These are formed of probably fluviatile coarse sands and gravels, which may be contemporaneous with the reef knolls.

As outlined here, the geology of Kabaena appears very simple. Almost certainly, this is due to the fact that work on the island was limited to a period of only five days. Even within that time, two anomalies were apparent. The river immediately east of Enano, despite being remote from any significant areas of high ground and close to roadside exposures of metamorphic rocks, is full of ophiolitic float and there is a possible outcrop of basic rock in the river bed just to the north of the grid. Also, the spectacular crest of Batusangia, at a height of well over 1000m, appears (from a distance, at least), to be formed of a coral reef knoll similar to those seen at much lower level in the median valley. One possible explanation for both these observations is that there has been strongly differential uplift of individual blocks now forming Kabaena.

Geologically, Kabaena seems very similar to much of eastern Sulawesi, especially those parts north of the Lawanopo Fault, where ultramafic rocks are most plentiful. Despite recent publications (e.g. Maury et al.), many problems remain in East Sulawesi geology. It is not clear whether the ophiolites all have the same provenance or are members of two or more ophiolitic suites. Opinions differ as to whether they formed in a back-arc basin or a supra-subduction zone (forearc) environment. The history of metamorphism is also unclear, and there is little or no geobarometric control. Although blueschists have been reported from the nearby Rumia Mountains of the Sulawesi mainland, the majority of the metamorphic rocks of Sulawesi have been described as greenschists, indicating relatively normal pressure-temperature relationships. Further work on Kabaena should be directed towards shedding further light on the evolution of the East Sulawesi block. A certain amount of straightforward mapping work is required, but the most important results will come from the laboratory.

HERPETOFAUNA

Kabaena is characterised by a mountainous terrain, dominated by ultrabasic marine sediments, whereas Buton is dominated by more recent limestone deposits. Although the annual rainfall of Kabaena is similar to that of Buton, the wet and dry seasons are more pronounced on Kabaena. Collectively these factors have produced markedly different forest types and habitats on these islands. These differences, combined with the relative isolation of the two islands may have resulted in the development of markedly different faunal assemblages. This may be most strongly reflected in the herpetofaunal assemblage, which is potentially most sensitive to local altitudinal, climatic and forest structural differences, and least able to disperse across sea barriers. Knowledge of the herpetofauna of Kabaena Island is therefore an important component of characterising the herpetofaunal component of the biodiversity of this region of Sulawesi.

The survey was based in the vicinity of Enano in central Kabaena Island. Sampling was conducted between late August and late September 2001. A variety of methods were employed to sample the herpetofauna.

BIRDS

Four weeks was spent assessing the bird fauna of the forests and farmland areas of Kabaena Island.  Mist netting was performed at Tangkeno and Enano to supplement the observations.  The avifauna of coastal areas was excluded from this intial survey. Table 1 in the Appendix lists the species identified from the 2001 survey.

The aim of the Kabaena 2001 small mammal project was to carry out a baseline biodiversity survey of the small mammal fauna. The small mammal fauna of Kabaena has not previously been studied, and it is important to begin to establish the range of species present. A large proportion of Sulawesi small mammals are endemic, and therefore of high conservation value.

The survey took place between the 5^th and the 20^th September, and was based predominantly in disturbed forest located around the village of Enano in the central region of Kabaena. Some additional trapping was also carried out from the 12^th to the 15^th September in disturbed forest adjacent to Pongkalaero, a village on the south-west coast of the island.  Four sites were selected at Enano; two were located on the south face of a ridge to the north of the village, and two to the south. Of the sites to the south, one was located on a river terrace, and the second on the north face of a ridge. Traps were also set at one site at Pongkalaero, at the base of a ridge approximately one to two kilometres east of the village.

Twenty wire cage Tomahawk traps, and 30 Longworth traps were available for use on Kabaena. The Tomahawks were set to trap the larger rodent species, and the smaller Longworth traps used for the smaller rodents and shrews. All traps were baited with a standard small mammal bait consisting of peanut butter and oats.  Each site to be trapped was reconnoitered, and a selection of traps were then set in positions which showed evidence of small mammal use (for example burrows, faeces or feeding remains). If no clear evidence was present, traps were set in locations which provided habitat features which might be used by small mammals (e.g. logs, tree buttresses, rock piles).  After an initial trapping period at all sites, trapping effort was concentrated on the two sites south of Enano which were yielding the best range of specimens, including potentially undescribed species.

All traps were checked each morning, and re-baited where necessary. Morphometric data was collected for all captured animals; this included sex, reproductive state weight, length of head and body, hind foot and tail. In addition a brief description of other identifying features was taken down, for example pelage colour and texture. A small DNA sample was taken from the ear of all captured animals. A small number of individuals of each species captured were taken as specimens. Some specimens will be lodged in the collection of the Bogor Museum and the remainder will be sent to Dr. Guy Musser at the American Museum of Natural History in New York for identification.

Over the course of the study 46 individuals of at least ten species of small mammal were captured, consisting of three shrew species, two mouse species and at least five species of rat. A total of 32 specimens were collected.

Of the shrew species, the majority of captures consisted of an undescribed species of Crocidura. The other species trapped were C. elongata and C. levicula.

Only one specimen of each mouse species was trapped; these species have yet to be identified.

Of the rat species trapped, one was readily identified as Paruromys dominator (the Sulawesi giant rat). Two specimens in the genus Bunomys were taken, but these have not yet been identified to species level. Two specimens of a suspected Rattus were also trapped; the species has yet to be determined.

The remaining specimens consisted of a number of rats that could not be allocated to any described species. These individuals showed some unusual features which indicate that they may belong to a new species. One group of specimens consisted of medium to large sized rats, with the males displaying a very distinctive large single scent gland located on the ventral centre line. The gland was up to 1cm in width, and ran for several centimetres from the genital area towards the chest. A single individual of an extremely small rat species was also trapped; this also possessed a single ventral scent gland, but in addition had spiny pelage. These features have not been described for any species previously recorded in Sulawesi.

This initial project has produced some very interesting findings, and shows that the small mammal fauna of Kabaena may warrant further study. Little is known about the ecology of the endemic small mammal fauna of Sulawesi, or about the potential impact of human activity resulting in habitat loss or degradation.

MACAQUES

BATS

Despite its current vicinity to Buton, Kabaena Island is thought to have been associated with the South-east arm of Sulawesi since the Tertiary, contrasting with Buton’s relatively recent arrival from Melanesia in the Late Miocene. The topology and habitat differ dramatically from Buton, and a preliminary survey in 2000 suggest that the extensive karst limeston cave systems of Kabaena support large and diverse populations of both fruit-eating and insectivorous bats. There is considerable evidence that roosts may be limiting for many bat species, and caves maybe pivotal to local survival when alternative roost sites, such as large hollow trees are reduced by forest clearance. Forest loss is a conservation issue on Kabaena, and as a consequence the cave systems may represent a keystone resource for the bat fauna of Kabaena.

CONCLUSIONS

This initial survey has shown that Kabaena for the most part has a subset of the fauna found on Sulawesi, with some notable omissions.  Small islands have been shown to support a smaller assemblage of species than larger islands in the same area and the finding that Kabaena has a subset of the Sulawesi fauna is therefore not surprising.

There were, however, some differences between the fauna of Kabaena and either Buton or mainland Sulawesi with the discovery of 2 small mammals, at least 2 freshwater fish, the ground thrush, three reptiles and one snake all of which may be new to science.  It should be noted though that this survey was carried out in the dry season and the frog fauna were therefore difficult to survey.  In addition both the freshwater fish and small mammal teams need additional survey time on Kabaena to complete their assessments.

The best remaining forest and the area from which most of the new species were sampled, was a mountain valley near Enano.  This valley has pristine forest and appears too inaccessible to have suffered from logging.  This was the only forest area on Kabaena that was noted by the survey team as being worthy of protection.

It is therefore proposed that Operation Wallacea requests that the Department of Forestry and Wildlife Conservation give protected forest status to the mountain valley near Enano , to preserve the unique fauna of the island.  In addition a follow up survey of the frogs, freshwater fish and small mammals in this mountain valley is scheduled in the Operation Wallacea survey programme for the end of the wet season in 2002 to add more details about these groups in the proposed protected forest area..

APPENDIX

TABLE 1

Table 2    Bird species recorded from Kabaena Island