Some notes on the butterflies (Lepidoptera: Papilionoidea) of Tantirimale Archaeological Site, Anuradhapura District, Sri Lanka
M.D.C. Asela 1, R.A.K. Peiris 2, S.K.I.U. Priyankara 2, R.W. Jayasekara 2 & D.M.S.S. Karunarathna 3
1,2,3 The Young Zoologists’ Association of Sri Lanka, Department of National Zoological Gardens, Dehiwala, Sri Lanka
Sri Lanka is an island situated between 05054’-09052’N & 79039’-81053’E. The Western Ghats and Sri Lanka comprise one of the biodiversity hotspot of the world (Meegaskumbura et al. 2002; Bossuyt et al. 2004). The total extent of natural forests in Sri Lanka constitutes over 12% of the total land area (Tan 2005). The natural forests in the island are rapidly diminishing as a result of the expansion of settlements and agricultural land, leading to adverse impacts on the rich biodiversity (Senanayake et al. 1977; Bambaradeniya et al. 2003).
Butterflies comprise a group of charismatic insects in Sri Lanka, which forms a major component of the island’s biodiversity. The total number of butterfly species recorded from Sri Lanka is 243, of which 20 species are endemic to the island (Woodhouse 1952; D’ Abrera 1998; van der Poorten 2005; Perera & Bambaradeniya 2006). The butterfly fauna of the study area has not been studied previously. The main objective of the present study was to conduct a brief survey so as to achieve an understanding of the butterfly species diversity at Tanthirimale Archaeological Forest Area (TAF).
Thanthirimale Archaeological Forest Area (120 ha.) is situated in the Maha Villachchiya Divisional Secretariat in Anuradhapura district at 8040’13’’N & 80017’27”E. Tanthirimale is 24km from Anuradhapura and can be reached via Anuradhapura Maha Villachchiya road from Sri Vimalagnana Mawatha junction or Meadavachchiya - Mannar road from Gajasinghapura junction. The boundaries of Tanthirimale are demarcated by Malwathu Oya in the north and east, Wilpattu National Park in the west and by Maha Villachchiya main road in the south (Chandarathana 2004).
The forest in the area is classified as “Tropical dry mixed evergreen forest” dominated by Manilkara sp. (Gunathilake & Gunathilake 1990). Geographically it is in the dry zone of Sri Lanka.
Archaeological findings from this location have revealed that this area has been inhabited by humans in the pre-Buddhist era (about 2600 years ago). Therefore, it is one of the earliest human habitations of Sri Lanka.
The study duration was for nine days, from 9 July 2005 to 17 July 2005. Observations were carried out for 7.5hrs per day, consisting of three sessions of 2.5hr each: 0600 to 0830, 1100 to 1330 and 1530 to 1800 hrs. The weather was dry and sunny with no precipitation or cloudy sky. Identification of butterflies was done in the field. Smaller butterflies were caught using a hand net and after identification, the specimens were released to the same habitat from where they were caught. Some small butterflies were closely observed after placing them in a clear glass bottle. They were identified using Banks & Banks (1985), D’Abrera (1998) and Woodhouse (1952) field guides. Plants were identified with Ashton et al. (1997) and plant nomenclature is based on Senaratna (2001).
Results & Discussion
Based on the species composition and structure of plants, three major vegetation types were identified in the study area. These comprise (a) Dry zone forest area, (b) Rock outcrop forests with water pools and (c) scrublands (Fig. 1). Twelve species of butterflies were found in the forest area, seven species in the Rock outcrop area and 28 species in the scrubland (Table 2).
The forest canopy is relatively high rising to 20m. The overall canopy cover is about 60%. The dry zone evergreen forest is mainly composed of Palu Manilkara hexandra, Weera Drypetes sepiari, Kon Schleichera oleosa and a few Ebony Diospyros ebenum) trees. It is a small, disturbed forest patch with a lot of scattered scrubland plant species. The average height of the scrubland vegetation is about 2.5m and is dominated by Korakaha Memecylon umbellatum, Eraminiya Zizyphus oenopila, Diwul Limonia acidissima, Kohomba Azadirachta indica, Ehala Cassia fistula, Kala Wel Derris trifoliata and Myla Bauhinia racemosa.
In the rock outcrop forests the number of plant species is low. Nabada Vitex leucoxylon, Kumbuk Terminalia arjuna and Timbiri Diospyros malabarica grow near water. Some Acacia plants were observed in the rock outcrop forests.
During the study period 37 butterfly species belonging to four families were observed. We could not record a single endemic butterfly during the field survey. The highest diversity of butterflies was recorded in scrubland which was rich with a variety of flowers and larval food plants while the lowest diversity was recorded in Rock Outcrop. The family with the largest number of species was Nymphalidae (18 species), followed by Pieridae (8 species), Papilionidae (6 species) and Lycaenidae (5 species).
Common Sailer Neptis hylas (Image 1), Dark Blue Tiger Tirumala septentrionis, Plain Tiger Danaus chrysippus, Common Tiger Danaus genutia (Image 3), Tawny Coster Acraea violae, Common Pierrot Castalius rosimon (Image 5), Lesser Grass Blue Zizina otis, Common Cerulean Jamides celeno (Image 2) were dominant in scrublands. Lesser Albatross Appias paulina and Common Indian Crow Euploea core were mostly observed in forest areas. Common Grass Yellow Eurema hecabe and White Four-Ring Ypthima ceylonica were observed in both forest and scrublands (Table 1).
Among the butterflies, Lesser Albatross Appias paulina and Quaker Neopithicops zalmora are nationally threatened taxa as notified by IUCN Sri Lanka (IUCN SL 2000).
Isolation is the main threat to the Tantirimale forest, close to Vilpattu National Park is surrounded by paddy fields, villages and roads. During May and June (Vesak and Poson) anthropogenic environmental disturbance occurs more due to pilgrims in addition to other factors like fire, logging, gem mining, pesticide application and road kills. Alien invasive species Gandapana Lantana camara grows in the scrubland area. Enhanced conservation efforts are required for TAF.
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