A Regenerating Rainforest in Sri Lanka
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Mahausakande Tropical Rainforest Regeneration Initiative Research Paper No. 1, January 2012 DIVERSITY OF HERPETOFAUNA IN MAHAUSAKANDE: A REGENERATING RAINFOREST IN SRI LANKA Mendis Wickramasinghe Channa Bambaradeniya Dulan Vidanapathirana Suranjan Karunaratna TECHNICAL PARTNER DIVERSITY OF HERPETOFAUNA IN MAHAUSAKANDE: A REGENERATING RAINFOREST IN SRI LANKA Citation: Wickramasinghe, L.J.M., Bambaradeniya, C.N.B., Vidanapathirana, D.L., and Karunarathna, D.M.S.S. (2012). Diversity of Herpetofauna in Mahausakande: A Regenerating Rainforest in Sri Lanka. Mahausakande Tropical Rainforest Regeneration Initiative, Research Paper No.1, 40 pp. © 2012 Ellawala Foundation Trust For more information about the Mahausakande Tropical Rainforest Regeneration Initiative, please visit http://mahausakande.org EXECUTIVE SUMMARY A systematic survey was conducted to assess the diversity of herpetofauna in the Mahausakande regenerating tropical rainforest (MRF) in Kiriella, Sri Lanka. Approximately 900 man hours were spent in the field over a period of four months to document amphibians and reptiles in representative habitat types, using different sampling methods. A total of 21 species of amphibians and 45 species of reptiles were recorded from MRF, of which 15 amphibians and 26 reptile species are endemic. The reptiles include 24 species of snakes, and 21 species of tetrapod reptiles. Among the endemics were three amphibian genera and six reptile genera. Two specimens of burrowing snakes (Typhlops sp.) collected may be new to science, and these will be further examined in the future. The most common species observed in MRF include the Common Paddy Field Frog (Zakerana syhadrensis), Zara’s Hump-nosed Viper (Hypnale zara), and the Kangaroo Lizard (Otocryptis wiegmanni). Of the total herpetofaunal species recorded in MRF, 11 species (16%) are considered as nationally threatened. The survey recognized several species of amphibians and reptiles that could be used as important ecological indicators to monitor the quality of habitats in the Mahausakande regenerating forest. The findings of the survey resulted in a two-fold increase in the herpetofaunal species recorded in MRF. The data gathered from the survey was also used for upgrading the IUCN National Red List. Contents EXECUTIVE SUMMARY .................................................................................................................................. 1 1. INTRODUCTION ......................................................................................................................................... 1 1.1 Species Richness and Diversity of Herpetofauna in Sri Lanka ........................................................... 1 1.2 The Study Area ................................................................................................................................... 1 1.3 Rationale ............................................................................................................................................. 1 1.4 Research Hypothesis ........................................................................................................................... 2 1.5 Objectives ........................................................................................................................................... 2 2. METHODOLOGY ........................................................................................................................................ 3 2.1 Study Methods .................................................................................................................................... 3 2.2 Specimen Collection and Identification .............................................................................................. 4 2.3 Documentation of distribution patterns ............................................................................................. 4 2.4 Evaluation of the Conservation Status of Species .............................................................................. 4 3. RESULTS AND DISCUSSION .................................................................................................................... 5 3.1 Species Richness of Herpetofauna in MRF .......................................................................................... 5 3.2 Relative Abundance of Herpetofauna in MRF .................................................................................... 6 3.3 Diversity of Herpetofauna in Different Habitats of MRF .................................................................... 7 3.4 Habitat Affinities of Herpetofauna in MRF ....................................................................................... 11 4. CONCLUSIONS AND RECOMMENDATIONS ......................................................................................... 12 REFERENCES ................................................................................................................................................ 14 ACKNOWLEDGEMENTS ............................................................................................................................... 17 Mahausakande Tropical Rainforest Regeneration Initiative Research Paper No. 1 Diversity of Herpetofauna in Mahausakande 1. INTRODUCTION 1.1 Species Richness and Diversity of Herpetofauna in Sri Lanka The wide array of natural ecosystems in Sri Lanka harbors a rich herpetofauna, represented by 111 species of amphibians,1-9 84 species of inland snakes,10-15 and 102 species of inland tetrapod reptiles.16-22 Among them, 93 species of amphibians, 49 species of serpents, and 76 species of tetrapod reptiles are endemic to Sri Lanka. Majority of the endemic herpetofauna are restricted to the central and southwest region of the island. Studies conducted over the last two decades have led to the discovery of several new species of herpetofauna in the island. However, degradation of natural habitats due to harmful anthropogenic activities has resulted in a decline of herpetofaunal populations. According to a national assessment of the conservation status of plant and animal species in Sri Lanka, 108 species of herpetofauna (34%) are considered as nationally threatened, with a majority of them (81%) being endemic species.23 1.2 The Study Area The Mahausakande regenerating tropical rain forest (MRF) is situated in the Ratnapura district of the Sabaragamuwa Province of Sri Lanka. The site consists of approximately 40 acres spread across a hilly terrain, with its altitude ranging from 80-1100 m asl. The site was managed as a rubber plantation till year 2003, which was subsequently abandoned in order to initiate a restoration program to establish a tropical rainforest. The area receives an annual rainfall of over 4000 mm, and the mean temperature is around 310 C. Two streams flow across the MRF site. The habitat types of the site consists of abandoned rubber, agricultural land, regenerating forest, secondary forest, rock-outcrop, riparian forest, manmade ponds and home garden. Preliminary investigations carried out at the MRF from 2004-2010 has documented 8 species of amphibians, 15 species of snakes, and 12 species of tetrapod reptiles.24 1.3 Rationale The Mahausakande tropical rainforest restoration initiative provides a unique opportunity to study the temporal changes in biodiversity associated with tropical forest regeneration. The herpetofauna can be used as valuable indicators to monitor the progress of species colonization associated with forest regeneration. Therefore, a systematic study was undertaken to document the diversity and richness of herpetofauna associated with the different habitat types of MRF. January 2012 Page 1 Mahausakande Tropical Rainforest Regeneration Initiative Research Paper No. 1 Diversity of Herpetofauna in Mahausakande 1.4 Research Hypothesis The hypothesis investigated through the present research is highlighted below: 1. The diversity of the herpetofauna in MRF has not been adequately documented through a systematic investigation; and 2. The species richness and abundance of herpetofauna in MRF may be correlated with habitats under different stages of forest regeneration and anthropogenic influence. 1.5 Objectives The present survey intended to fulfill the following objectives, related to the taxonomy and conservation of the herpetofauna in MRF: 1. Update the knowledge base on the occurrence of herpetofauna in MRF, including the potential discovery and description of new species. 2. Determine the current distribution pattern and habitat relationships. 3. Establish a database on herpetofauna in MRF for future monitoring. 4. Contribute towards future conservation awareness programmes at MRF. January 2012 Page 2 Mahausakande Tropical Rainforest Regeneration Initiative Research Paper No. 1 Diversity of Herpetofauna in Mahausakande 2. METHODOLOGY 2.1 Study Methods Field observations were made over a period of four months, extending from April to July 2011. A combination of methods was adopted to study the diversity of herpetofauna associated with all of the representative habitat and microhabitat types in MRF. These included litter cleaning methods (LCM), Digging loose soil (DLS), and Visual encounter surveys (VES) during day and night time. The use of pitfall traps was avoided, since it could result in herpetofaunal mortality and/or predation, and also disturb forest regeneration. The sampling replicates in each habitat type are summarized in Table 2.1 below: Table 2.1: Sampling replicates per habitat type Canopy Habitat types