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46 Seiten, Note: D
“An amphibian is the first “actor” in the evolution of life on land”. Amphibians are the first vertebrate animals to have two completely different life stages, one as tadpoles that generally occur in water and other as adults that are living more on land (Duellman and Trueb, 1994). Amphibians are vital components of healthy environment. Presence of good population of amphibian in a region is indication of a healthy environment (Gururaja et al., 2008). Amphibians play a major role in ecosystem functioning, as prey and predator, especially as consumers of pest insects. Amphibians have backbones. The skin is equipped with glands that secrete mucous and poison, but lacks external structures such as feathers and hairs. Amphibian eyes when present are large. Hearing is well developed in amphibians as they have specialized inner ears. Specially designed vocal sacs located on the throats of male frogs and toads amplify the calls, carrying the sounds over long distance and aid in attracting females at the time of breeding.
The number of known extant amphibian has increased rapidly in recent years with over 2700 species. The amphibian fauna of India comprising of caecilians, frogs , toads and salamanders is extremely diverse (Dinesh et al.,2009) and has high level of endemism in the Western Ghats and Eastern Himalayas (Inger, 1999; Biju and Bossuyt 2003; Roelants et al., 2004; Aravind et al., 2004). India harbours 311 species amphibians belonging to all the extant orders Caudata, Anura and Gymnophiona.
Amphibians as indicator taxa
Amphibians are considered as ‘Canaries in a coal mine. There are debates on whether amphibians truly act as canaries or others species have more sensitivity than amphibians (Kerby, 2010). Despite setting aside whether they are canaries or not, they are still in a coalmine. Recent studies in the Western Ghats also have emphasized that amphibians are the best surrogates for conservation priority regions (Das et al., 2006) and Philautus is considered as an indicator of fragmented forests for its patchy distribution (Gururaja et al., 2007).
The Western Ghats, a chain of hills of varied width and height running parallel to the western coast of India, is a hotspot of biological diversity (Myers et al., 2000). It is a chain of mountains that runs parallel with west coast of India over 1600 km from 8 º15 N to 21º 00 N .The mountain range begins as low lying hills in the North western state of Gujarat and then passes southwards through Maharashtra, Goa, Karnataka and Kerala, before ending abruptly in Mahendragiri hills in Tamil Nadu at the southern tip of Peninsular India. The chain of hills interrupted by the biogeographically important Palghat gap at around 10º 31 N,76 º31 E which is an area of approximately 30 km in width with an elevation of less than 100 m ASL (Biju and Bossuyt, 2009). This region harbours a high proportion of endemic species, especially in lower vertebrate group such as amphibians and reptiles (Daniels, 2001 and Dahanukar et al., 2004). During monsoon between June and September the unbroken Western Ghats chain act as a barrier to the moisture laden clouds. An average rainfall in this region 3000 - 4000 mm with localised extreme touching 9000 mm. The Western Ghats are home to four Tropical and Subtropical moist broad leaf forest eco regions.
Region of high diversity and endemism
The Western Ghats has a high diversity and endemism of amphibian species with 181 known species, (including new species described in recent years) of which 159 (88%) are endemic to the Western Ghats (Aravind & Gururaja, 2011; Bhatta et al., 2011; Zachariah et al., 2011).Few new species of Anurans belonging to the genus Rhacophorus, Polypedatus, Philautus have been described from the Western Ghats. Amphibians within the Western Ghats hotspot shows very high level of endemism or local endemism especially in the genera Raorchestes Compared to other bio-geographic regions of India, the Western Ghats harbour high diversity for amphibians. There are several regions with in the Western Ghats hotspots which sustains high diversity and endemism.
These frogs belong to the family Rhacophoridae. The family Rhacophoridae is widely distributed in the tropical regions of Africa and Asia. Tree frogs, bush frogs, gliding frogs and flying frogs are belongs to this family (Daniels,2005). The Rhacophoridae constitute a radiation of about 300 species of frogs with a distribution in the tropical region of Asia and Africa (Biju, et al. 2010). Almost all species in this family are tree dwellers and are characterized by the enlarged disc on the fingers and toes. These frogs are capable of taking long leaps from one place to another. Many species in this family are brightly coloured. They vary in length from 1.5cm to 12 cm. amongst the bush frogs, most species lay eggs between leaf folds or directly in water. A few species are even known to develop directly from the eggs without a free living tadpole stage. In those species where direct development in the mode of reproduction, parental care is prevalent to certain extent (Daniels, 2005).
Philautus is a genus of shrub frogs in the family Rhacophoridae. This genus is characterized by direct development that is the attainment of the adult morphology without going through a free living larval phase (Bossuyt and Dubois, 2001; Callery et al., 2001). Some species have been found to bury their eggs in soil although they are arboreal and others attach their eggs to leaves. Bossuyt and Dubois (2001) recognized 110 valid species names in the genus Philautus. The anuran fauna of the Western Ghats is extremely diverse, both in terms of species richness (Dutta, 1997; Das, 2000;Bossuyt, 2002;Kuramoto and Joshy, 2003).The highest density in this genus is found in the Western Ghats of India and Srilanka. In the world there are 146 species of Philautus to be found. This genus Philautus is restricted to the Western Ghats with 39 species (Zachariah et al., 2011).
The genus name “Philautus” is changed into genus “Raorchestes ” because the generic epithet is derived from the name “Rao” and the scientific nomen “orchestes”. The former is chosen in honour of C.R. Narayana Rao, in recognition of his contribution to Indian battrachology. The latter is based on the first generic nomen coined for frogs of Philautus group orchetes Tschudi 1838 (Biju et al., 2010). The genus Raorchestes was erected by (Biju et al., 2010) based on molecular phylogenetic studies. This genus Raorchestes distinguish different kinds of taxognoses and define the new genus according to the following characters.
- Nostril rounded or oval
- Pupil oval horizontal
- Tympanum rounded
- Vomerine teeth are absent, tongue emarginated
- Arms short
- Tips of the fingers & toes with discs,
- Thigh and shank slender, belly granular
- Males have a large vocal sac when calling, and have a pair of gular slits at the base of the lower jaw.
- Female has a relatively low (22-62) number of large unpigmented eggs .
- All species undergo direct development (Biju and Bossuyt, 2009).
The Nilgiri district derives its charm from its natural setting, high above the sea level, situated at the junction of two Ghats ranges of the Sahayadri hills. The steep hills and fantastically narrow valleys with numerous rivers and rivulets running in all directions with a few waterfalls. The total area of the district is 2366.89sq.km. This district comprises 4 taluks, 4 blocks and 54 villages. The monthly average rainfall in the district has been 94.20 mm. The months of June, September, October and November receive a rainfall that is more than the annual average rainfall. Mean minimum average temperature of 9.6C and mean relative humidity maximum of 76.9 and minimum of 75.8.Any data on amphibians is thus of both immediate and potentially broader interest. Continued habitat loss due to development projects, intensified agricultural and plantation practices could easily have led to species extinction before rediscovery and understanding their role in natural ecosystem. Existing information, particularly on amphibians were based mostly on old collection materials and literatures. Hence, updated information on amphibians is very important to formulate action plan for their conservation. Therefore this study was formulated to list out the diversity of amphibians and to assess existing threats for their survival in Nilgiris District.
Amphibian diversity in the Nilgiris is under threat due to the expansion of plantations and townships. Large scale conversion of land into cultivable fields, air pollution due to vehicular inflow, contamination of water bodies, streams and ponds by the indiscriminate discharge of chemicals and toxic effluents and spraying of chemicals, fertilizers and pesticides, pose grave threat to the survival of the endemic amphibians particularly the bush frogs of the genus Raorchestes . Recently there is a lot of change in the taxonomy of amphibians. Very few studies have been conducted on the site record an amphibians particularly with reference to the bush frogs.(Zachariah et .al, 2011).There is no detailed study on the ecology of bush frogs in Ooty area. Hence it is decided to study their current taxonomic positions of bush frogs, their habit, habitat and distribution pattern in Nilgiris which would pave the way for planning for their effective conservation measures.
The main objectives of this study are to
- Study the current taxonomy of bush frogs (genus: Raorchestes ) in and around Ooty Nilgiri Biosphere Reserve, The Western Ghats.
- Know the micro and macro habitats of bush frogs in and around Ooty
- Develop a species list of bush frogs (Genus: Raorchestes ) in and around Ooty, The Nilgiris.
- To know the diversity and distribution pattern of bush frogs in disturbed and undisturbed habitats in and around Ooty, Nilgiri Biosphere Reserve, The Western Ghats.
- To find out the existing threats and to prepare an action plan for their conservation.
Nilgiri Biosphere Reserve encompassing an area of 5520 s q km and covering parts of Tamil Nadu, Karnataka and Kerala. It is located between 76o-77o15’E and 11o15’-12o15’N. The annual rain fall of the reserve ranges from 500 mm to 700 mm with temperature ranging from 0oC during winter 41oC during summer. The altitude ranges from 250 m to 2600 m. Huge variations in rain fall, temperature, altitude, wide diurnal range of temperature and high solar radiation over a short area as the cause of variation in vegetation types. The Nilgiri Biosphere Reserve falls under the biographic region of the Malabar rain forest. The Nilgiri Biosphere Reserve is the home for many endemic species of the Western Ghats. Among the 285 species of vertebrates endemic to the Western Ghats, 156 (55%) are found in the NBR (Daniels, 1993). This includes 31 species of amphibian.
Ooty or Udhagamandalam rightly described as “Queen of hills station” by Pandit Jawaharlal Nehru, sprawls over an area of 36 sq.km. It is situated at an altitude of 2,240 meters above sea level. One can notice that many changes in vegetation, as one goes from Kallar to Coonoor. The vegetation is varied types according to the environmental conditions.
In the study area four different localities have been selected keeping in mind attributes like differences in latitudinal positioning difference in altitudinal range.
- Doddabetta (Natural vegetation )
- Government Arts College campus and its surroundings (Human habitation )
- Finger post (Agricultural area)
- Forest Gate (Plantation or monoculture)
1. DODDABETTA (Natural vegetation )
Doddabetta peak , 4km east southeast from Udhagamandalam, lies between 11°24′10″N76°44′14″E / 11.40278°N 76.73722°E / 11.40278; 76.73722 (Doddabetta Peak), with a height of 2,637 metres (8,652 ft) is the highest point in the Nilgiris and the southern extent of the range. It lies at the junction of the Western Ghats and Eastern Ghats and offers beautiful visitors of the Nilgiri hill range. It is surrounded by dense sholas. Sholas covers the hollows of its slope slightly stunted rhododendron tree in the midst of thick coarse grass flowering sub-alpine shrubs, herbs are common even very peak. The soil predominantly lateritic with sparse limestone patches. PH of the soil is around 4.0 and it is poor in nitrogen, deficient in phosphate, potassium and calcium. Through rainfall is dispersed in two distinct monsoons from May to September and November to December respectively two six months cycle, one representing the wet and other relatively dry weather are noticed. Thus the average precipitation in the area is around 103.5 cm during June to November about18.5 cm between December to May. Temperature range between 2deg Celsius to 28 deg. Celsius lowest range of temperature recorded during winter nights and the highest on summer days.
2. GovERNMENT Arts College campus AND ITS SURROUNDINGS (Human habitations)
The college location is called as stone house hill named after the landmark building stone house. The area is surrounded by shrubs and herbs and few species of trees. It is the home for many migratory birds and local birds. The GPS reading of this area is 11°24′50″N76°42′42″E / 11.413783°N 76.71154°.So many houses, buildings and commercial buildings are found in this area.
1. Finger post ( Agricultural areas )
In finger post most of the area is changed into human dwellings. The forest is scattered throughout the area. It has shola trees, Eucalyptus, Wattle and Pinustrees.
1. Forest GatE (Plantation or monoculture)
This area is covered by forest and plantations. Above plantation below water with wet vegetation is suitable for the amphibian population in that area. There are many varieties of tree species are found here they are Eucalyptus, Wattle, Blue gum. During heavy rain these slopes are easily washed away resulting in a land slide.
Plate 1: Study site 1-Doddabetta, Nilgiri Biosphere Reserve
Abbildung in dieser Leseprobe nicht enthalten
Plate 2: Study site -2 Government arts college and its surroundings.
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