|Reptiles of Sri Lanka
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|Author:||Rohan2 [ Thu Sep 13, 2007 1:45 pm ]|
|Post subject:||Reptiles of Sri Lanka|
Reptiles of Sri Lanka
Sri Lanka ranks as a great herpetological paradise in the world. Reports published to date (2005) list 183 reptile species in Sri Lanka, of which 104 are endemic. Deforestation, with consequent loss of wildlife habitats and habitat fragmentation, is the biggest threat faced by Sri Lanka's herpetofauna.
By Anslem de Silva (2005), Herpetologist,
Amphibia and Reptile Research Organization of Sri Lanka, (ARROS)
15/1 Dolosbage road, Gampola, Sri Lanka
Carl Linnaeus [1707-1778] described the first reptile (Cylindrophis maculata) from Sri Lanka in 1754. Since then, a host of subsequent workers included descriptions of reptiles from Sri Lanka in their publications during the 18th, 19th, 20th and 21st centuries.
The reptile fauna of Sri Lanka is highly diverse and shows affinities to that of the Western Ghats of peninsular India. Though the wet zone of Sri Lanka is remarkably similar to the Western Ghats region in India, it is considered the ‘least influenced by recent invasion from southern India’ (Crusz & Nugaliyadde, 1977). In fact, recent molecular studies of some amphibians and uropeltid snakes show that Sri Lanka has maintained a fauna distinct from that of the Indian Mainland (Bossuyt et. al., 2004).
Knowledge of the Sri Lankan reptiles, however, is largely limited to species descriptions and basic information. The general and systematic treatments on the reptiles of Sri Lanka consist of outdated classics, such as those of Malcolm A. Smith (1933, 1935, 1943), Edward H. Taylor (1950a, 1950b, 1953), Paulus E. P. Deraniyagala (1953, 1955), P. H. D. H. de Silva (1980, 1969), and Frank Wall (1921). Three genera have been revised recently with descriptions of new species: Aspidura (Reptilia: Ophidia: Colubridae) by Gans & Fetcho, 1982; Lankascincus (Reptilia: Scincidae) by Greer, 1991 and Ceratophora (Reptilia: Agamidae) by Pethiyagoda & Manamendra-Arachchi, 1998. In addition five new species of geckos of the genus Cyrtodactylus was described by Batuwita and Bahir (2005).
Current taxonomic status of Reptiles in Sri Lanka
Reports published to date list 183 reptile species in Sri Lanka (Table 1), of which 104 are endemic (Deraniyagala, 1953, 1955; de Silva, 1990a, 2001, de Silva, P.H.D.H., 1980; Gans & Fetcho, 1982; Greer, 1991; Pethiyagoda & Manamendra-Arachchi, 1998; Smith,1933, 1935, 1943 and Taylor, 1950a, 1950b, 1953, Bahir & Maduwage, 2005; Bahir & Silva, 2005 and Batuwita & Bahir, 2005). This number includes the 5 species of marine turtles that visit the beaches of Sri Lanka for nesting and the 13 species of marine snakes (Family Hydrophiidae) that inhabit the coastal waters, estuaries, mangroves, and river mouths of the country.
Of the reptiles, six endemic genera comprising of 22 species of saurian reptiles (Chalcidoseps – 1 species, Lankascincus – 6 species; Nessia – 8 species) and three of agamid lizards (Ceratophora – 5 species; Lyriocephalus – 1 species; Cophotis – 1 species), are considered geographical relicts (Crusz, 1986; Greer, 1991, de Silva 2001). Likewise, five endemic genera of serpentoid reptiles — one uropeltid genus (Pseudotyphlops – 1 species) and four colubrid genera (Aspidura – 6 species; Cercaspis – 1 species; Haplocercus – 1 species; Balanophis – 1 species) are considered geographical relicts (Crusz, 1986; de Silva, 1990a & 1990b). Several new species of geckos, lacertids, skinks, and snakes that have been discovered recently await description.
Present Ecological status of Reptiles
Deforestation, with consequent loss of wildlife habitats and habitat fragmentation, is the biggest threat faced by Sri Lanka's herpetofauna. The rate of depletion of forests and wild life habitats in Sri Lanka is considered one of the highest in South Asia (McNeely et. al., 1990). Forests were preserved untouched by the ancient rulers of the island as catchment areas and for security. Conservationists consider that the extensive felling of forests that took place during the last few hundreds of years would have had a tremendous impact on the endemic fauna of the country, as the majority of endemic amphibian and reptile species inhabit wet and intermediate lowland and montane forests. These forests today contain the most distinctive elements of the Sri Lankan reptile fauna that has been least influenced by recent invasions from the Indian mainland (Crusz 1984). During more recent times (commencing from the early 1980s) vast areas of the dry zone and monsoon forests were cleared once again under the Accelerated Mahaweli Project for agriculture and settlement.
The natural forest cover that was around 84% of the land area in 1880 is now reduced to 23% (Gunatilleke et al., 1995). Although there are laws and enactments pertaining to the protection of flora and fauna, these are routinely violated. Typical examples are the marine turtle hatcheries and the large scale robbing of turtle eggs and killing turtles for their flesh. The International Institute for Environment and Development (1992) and the Central Environmental Authority (1988) of Sri Lanka state that the enforcement of these laws has been very ineffective. They are outdated and have glaring inadequacies.
Reptiles are adaptable and less extinct-prone than most other vertebrates (Wilcox, 1980) that adapt poorly to environmental changes. This could be a reason we witness appreciable populations of many reptile species. However, our studies indicate that many endemic and relict reptiles face numerous threats. In 1998 during a five-day CAMP workshop on amphibians and reptiles of Sri Lanka held at the University of Peradeniya, 119 reptile species were assessed using IUCN Red List (1994) criteria and 43 species were classified as Vulnerable, 27 Endangered and 18 as Critically Endangered (de Silva et. al., 2000). The IUCN Sri Lanka, using different criteria reflecting the data available in the country, has determined that 86 species are threatened (IUCN Sri Lanka, 2000). The leaf nose lizard (Ceratophora tennentii) was listed as an endangered reptile in the IUCN Red List for many years. These lizards inhabit only the montane forests in the Knuckles Mountain range. Senanayake (1980) considers that this species may become extinct if its habitat is lost due to clearing of the primary forests for cardamom (Elettaria cardamomum) plantations. A recent study at Knuckles (de Silva et. al., 2005a) indicates the presence of healthy and appreciable populations of Ceratophora tennentii widely distributed in the Knuckles Mountain range. However, it was observed that there is a marked decline of Cophotis ceylanica in the Knuckles Mountain range though appreciable numbers were observed in the late 1970’s and early 1980’s.
In contrast, recent studies indicate that some species of reptiles which were earlier considered rare (e.g. Lyriocephalus scutatus, Calodactylodes illingworthorum, Calotes liolepis, Balanophis ceylonensis, etc) in the country show the existence of healthy populations (de Silva et al., 2004 a, . 2004 b, de Silva et. al., 2005a, de Silva et. al., 2005b). They even occupy ranges larger than those hitherto reported by Deraniyagala (1953, 1955), P. H. D. H. de Silva (1980) and de Silva (1990a). In addition, the lack of data regarding the golden gecko (Calodactylodes illingworthorum) has led to the assumption that they were uncommon (e.g., Manamendra-Arachchi, 1997, Wickramsinghe and Somaweera, 2003). However, after investigating nearly 50 specific sites inhabited by the golden gecko, and counting the number of individuals sighted or heard in each of the study sites as well as the number of healthy egg clusters, it is our conclusion that Calodactylodes illingworthorum is the dominant gecko species in its range (de Silva et al., 2004a).
Most of the endemic fossorial reptiles (e.g. the species Chalcidoseps thwaitesii and the genus Nessia etc) when kept out from their niche for 10 to 15 minutes the skin commences to dry and would then proceed to shrivel up. Thus, the coolness and moisture content in its microhabitat is a critical factor for the survival of these fossorial relict reptiles. Chalcidoseps thwaitesii is mainly confined to the Knuckles ecosystem. Studies on the annual rainfall of the Knuckles Range have shown a decrease in the rainfall (Giragama & Madduma Bandara, 1993; Madduma Bandara 1991). In addition, the negative impacts of the cultivation of cardamom at the Knuckles have been extensively reported (Abeygunawardena & Vincent 1993; Gunawardane et al., 2003). Studies have shown that in natural forested areas without cardamom cultivation the ‘A’ horizon is well preserved and covered with mulch to a depth of 30-35 cm whilst in cardamom fields the mulch level has reduced to 15-25 cm (Madduma Bandara, 1991). This data is from a study conducted in mid 1980’s, thus, it is possible that at present this mulch level could be further reduced. When we measured the mulch level in some cardamom plantations at Kobonila in 2004, we found that it was less that 10 cm (de Silva et al., 2005). In addition, the soil erosion was high. Thus, we see possible long-term irreversible habitat degradation at the Knuckles that could affect the microhabitat of these and other fossorial animals that inhabit the cool moist humus and leaf litter of the forest floor and lay their eggs.
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