Of all the terrestrial vertebrate groups on Sulawesi the frogs are the most poorly known (Iskandar and Tjan 1996). Many species have not yet been formerly described (Iskandar and Tjan 1996), and there are likely to be many more taxa discovered in the future. In addition, virtually nothing has been documented on the life history or ecology of these species (Brown and Iskandar 2000).

Surveys conducted in the Labundo Bundo region in 2000 detected only 10 species of frog (Gillespie 2000). This number is relatively low compared with elsewhere in South-east Asia and tropical Australasia (Manthey and Grossmann 1997; Cogger 2000). At least three of these species are undescribed. This paucity of species may reflect a lack of diversity in suitable breeding habitats for frogs, or the lack of topographic/climatic variation in the area. Alternatively, it may be the result of the limited survey effort in the wet season when many species probably breed and are most readily detected.

At least five frog species were found that breed exclusively in streams. Riverine species are of particular interest because most of our understanding of anuran ecology has been gained from research undertaken on lentic species and communities (see Duellman and Trueb 1994; Alford 1999). Generalisations of anuran ecology may have limited application to riverine communities. The biotic and abiotic environmental constraints imposed on amphibians by streams, such as hydrology, and predator-prey relationships, are substantially different from those imposed by lentic habitats. Riverine environments have been considered ‘harsher’ than pond habitats (Inger et al. 1986), and specialised physiological and morphological adaptations may be required for survival in streams that preclude survival of pond species (Altig & Johnson 1989). In addition, the metapopulation dynamics of riverine species may differ from those of lentic or terrestrial species, due to the linear nature of streams. In addition, riverine species as a group have been severely affected by the global population declines of amphibians in recent years (e.g., Campbell 1999). The factor(s) responsible for many of these declines go beyond habitat destruction or degradation, and are poorly understood. There is currently limited information on the conservation status or population demography of any frog species in south-east Asia.

Most riverine frog species elsewhere around the world breed in permanent streams. The onset of the dry season on Buton Island in 2000 resulted in all but the largest of streams rapidly drying up. This undoubtedly has a marked impact on the reproductive biology and ecology of riverine frogs. Investigation of various aspects of the ecology, life history and population demography of riverine frogs in Buton Island is proposed.

Two monitoring transects have been established along selected streams. Frog censuses were conducted along each of these transects at night with head torches near the Kakenauwe reserve and in Lambusanga. Each transect was censused on a weekly basis throughout the expedition. During each visit, frogs were captured, measured and sexed, and marked by toe-clipping (see Donnelly et al. 1994; Hero 1989). Mark-recapture data gained from repeated censuses will be used to estimate population densities of each species (see Donnelly and Guyer 1994) and examine movement patterns. Information on weather conditions, such as air and water temperature and precipitation have also been recorded during each census. Relationships between climatic conditions and activity patterns of each species, including reproductive activity, have also been examined. Timing of breeding, egg-laying and larval development will be documented where possible. These transects would provide the basis for a longer term population monitoring program, which would complement similar programs being undertaken of both declining and non-declining species elsewhere in the world.

Oviposition sites of each species were located by observations of breeding activity of frogs along monitoring transects and active searches for egg masses. Taxonomic identity of egg masses were confirmed by rearing tadpoles in buckets in the stream. The position and physical structure of each egg mass was described and the number of eggs counted. Various aspects of the habitat structural characteristics of each oviposition site were recorded, such as the physical structure of the stream, associated banks.

Tadpole microhabitat associations were examined by systematic sampling of the distribution of tadpoles along monitoring transects. Timed dip-net sweeps were conducted in various stream microhabitats, such as riffles, cascades, runs, in-stream pools and isolated streamside pools. The numbers of tadpoles of each species were recorded in each sweep. Various physical habitat characteristics of each sample point were recorded, such as stream flow, depth, amount of litter, sand and rock substrata.

Relationships between relative abundance or occurrence of tadpoles of each species and habitat attributes of streams will be examined using standard multivariate statistical approaches, such as linear and logistic regression analyses.

Several voucher specimens of females of each species were collected during habitat surveys. These specimens were measured and weighed, then dissected and egg compliments, if present, counted. The mass and mean diameter of eggs was also calculated. A section of femur was removed from one hind leg of each specimen. The age of each frog will be determined from bone samples by skeletochronology. This technique allows reliable age determination through seasonal growth patterns of bones in organisms with indeterminate growth, such as amphibians. High density layers of bone (resting lines) are deposited during periods or seasons of slow growth, while low density bone is deposited during faster growth (see Castanet et al. 1993). This is accentuated in organisms that occur where seasonal differences in growth are more pronounced. Resting lines can be viewed clearly in stained cross-sections of long bones and counted to determine years since metamorphosis. This procedure will be conducted in Australia or the U.K. Age to sexual maturity will be determined, and relationships between body size, age and egg compliment examined for each species by linear regression, and compared among species by Analyses of Covariance. Egg compliments and voucher specimens will be lodged at the Bogor Museum.

Data analyses have not yet been undertaken. Preliminary examination indicates that population numbers of some species remain fairly constant throughout the study season, while those of other species increased substantially. This increased coincided with the onset of the breeding season for all riverine species, as evidenced by the occurrence of egg masses n the streams. These observations suggest that some species are resident along the stream, while others move to the stream after the wet season, prior to and during the onset of the breeding season.

One hundred and ninety tadpole censuses were conducted in streams in Central Buton Island. Preliminary results suggests that there is not strong habitat partitioning amongst species; most species occurring predominantly in slow-flowing sections of streams. Relationships between the occurrence of each species and various habitat characteristics will be examined by logistic regression analyses.

Egg counts were conducted for five species of frog: Limnonectes sp. nov. inflatus (3); L. sp. nov. modestus (2); Bufo celebensis (1); Rana chalconata (2); and Rhacophorus sp. (14). Substantial variation in clutch sizes was apparent, ranging from 14 eggs to over 3000. Sample sizes are currently too low for any detailed examination of clutch size relationships. More sampes will be collected next season.

A paper entitled Gillespie, G.R. Lockie, D. Scroggie, M.P. Iskander, T. (2003)  Habitat use of stream breeding frogs in south-easterm Sulawesi and some preliminary observations on community organisation has been submitted to Journal of Tropical Ecology.

References

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Brown, R. M. and Iskandar, D.T. (2000). Nest site selection, larval hatching and advertisement calls of Rana arathooni from southwestern Sulawesi (Celebes) Island, Indonesia. Journal of Herpetology, 34: 404-413.

Campbell, A. (ed.) (1999). Declines and Disappearances of Australian Frogs. Biodiversity Group, Environment Australia, Canberra.

Castanet, J., Francillon’Vieillot, H., Meunier, F. J., de Ricqles, A. (1993). Bone and individual aging. In: B. K. Hall (ed.), Bone, Volume 7: Bone Growth, CRC Press, Boca-Raton, Florida, USA.

Cogger, H. G. (2000). Reptiles and Amphibians of Australia. 6^th Edition, Reed New Holland, Sydney.

Donnelly, M. A. and Guyer, C. (1994). Estimating population size. In: W. R. Heyer, M. A. Donnelly, R. W. McDiarmid, L. Hayek and M. S. Foster (eds.), Measuring and Monitoring Biological Diversity – Standard Methods for Amphibians. Washington Smithsonian Institution Press, pp 183-205.

Donnelly, M. A., Guyer, C., Jutebock, E. and Alford, R. A. (1994). Techniques for marking amphibians. In: W. R. Heyer, M. A. Donnelly, R. W. McDiarmid, L. Hayek and M. S. Foster (eds.), Measuring and Monitoring Biological Diversity – Standard Methods for Amphibians. Washington Smithsonian Institution Press, pp. 277-284.

Duellman, W. E. and Trueb. L. (1994). Biology of Amphibians 2nd ed. John Hopkins. London.

Gillespie, G. R. (2000). Herpetofauna Biodiversity Survey of the Labundo Bundo region of Buton Island, Sulawesi Tengarra, Indonesia, July-September, 2000. Unpublished report.

Hero, J.-M. (1989). A simple code for toe clipping anurans. Herpetological review, 20: 66-67.

Inger, R. F. (1969). Organization of communities of frogs along small rain forest streams in Sarawak. Journal of Animal Ecology, 38:123-148.

Inger, R. F., Voris, H. K. and Frogner, K. J. (1986). Organization of a community of tadpoles in rainforest streams in Borneo. Journal of Tropical Ecology, 2:193-205.

Iskandar, D.T and Tjan, K. N. (1996). The amphibians and reptiles of Sulawesi, with notes on the distribution and chromosomal number of frogs. In: D. J. Kitchener and A. Suyanto (eds.), Proceedings of the First International Conference on Eastern Indonesian-Australian Vertebrate Fauna, Manado, Indonesia, pp. 39-46.