Literaturdatenbank
Literaturdatenbank |
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Vasudevan, K., Pandav, B., & Deepak, V. (2010). Ecology of two endemic turtles in the western ghats Wildlife Institute of India.
Added by: Sarina Wunderlich (25 Jun 2011 12:42:17 UTC) |
| Resource type: Report/Documentation BibTeX citation key: Vasudevan2010 View all bibliographic details  |
Categories: General Keywords: Geoemydidae, Habitat = habitat, Indotestudo, Indotestudo travancorica, Nilssonia, Nilssonia leithii, Schildkröten = turtles + tortoises, Südasien = Southern Asia, Testudinidae, Trionychidae, Vijayachelys, Vijayachelys silvatica Creators: Deepak, Pandav, Vasudevan Publisher: Wildlife Institute of India |
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| Abstract |
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This project was initiated on the 16th January 2006 with an aim to generate natural history information on two out of the three endemic species of terrestrial turtles. India has 28 species of freshwater turtles and tortoises, of them three species are endemic. The endemic species: Cane turtle, Vijayachelys silvatica; Travancore tortoise Indotestudo travancorica; Leith’s softshell Nilssonia leithii, are restricted to the southern peninsula and the Western Ghats. In this study the focal species were the Cane turtle and the Travancore tortoise which had their distribution in the Western Ghats. The objectives of the project were (i) to estimate the population density of Travancore tortoise and cane turtle in a fragmented landscape; (ii) to quantify the diet of these two species and describe the feeding ecology with respect to their role in seed dispersal; (iii) to identify threats to the turtle population based on their habitat use ranging pattern and food habits and recommend measures for their conservation; (iv) to carry out a survey of these two species along the Western Ghats to ascertain the exact distribution in the context of Protected area network in the region. The study employed methods to study the population, diet and ranging patterns of the Cane turtle and the Travancore tortoise in Anamalai and Parambikulam Tiger Reserves. In the case of Travancore tortoise, the animals were searched on forest trails scattered in the reserves and repeated over three years to determine the proportion of area occupied accounting for imperfect detections. These surveys revealed that about 82% of the area surveyed is occupied by the tortoise, suggesting that the reserves hold sizeable population of the tortoise. The occupancy of the Travancore tortoise was negatively influenced by anthropogenic disturbance levels and positively influenced by the availability of water bodies and grass marsh in different sites. Only 35% of the sites occupied by the species resulted in detections, suggesting that it was cryptic. The important constituents of its diet were grass, other plant matter, invertebrates and other animal matter. The vayal (grass openings within woodland) habitat might be crucial for foraging by Travancore tortoise. The five individuals that were radio-tagged used an area from 5 to 35 ha covering evergreen, bamboo and open scurb-grass marshes. The animals spent about 98% of their time under leaf litter, logs, rocks crevices, tree holes, termite or pangolin burrows, bamboo tickets and under grass. In the case of cane turtle, various search methods employed did not yield detections and therefore, an intensive area was combed intensively. This resulted in detections of the elusive cane turtle. During the study spanning over four years, 42 ha of the evergreen forests in the reserve resulted in sightings of 27 different individuals of the cane turtle. This suggests that the species occurs in high density in the evergreen forests. Six cane turtles were fixed with radio-transmitters and monitored for two years. They used an area from 3.5 to 14.2 ha restricted to the evergreen forests alone. They also had extensive overlap in their home-ranges, suggesting no territoriality in the species. The movement of the animals were influenced by temperature and rainfall in the intensive study area. Diet of the species consisted of forest floor invertebrates, seeds and other plant material. The field observations on feeding on a large land snail and aggressive encounters between males of the cane turtle were the highlights of the study on the species. A survey of the three endemic species of turtles was taken up in the fifth year of the project. The survey involved visiting 12 sites in the states of Karnataka and Tamil Nadu. The potential sites where the species might be found were visited and the locals were interviewed in order to document the occurrence of the species. This resulted in one new locality record for cane turtle and two new records for Travancore tortoise. The Leith’s softshell was reported from five different locations in Karnataka and Tamil Nadu based on the interviews with locals. The sites occupied by the species were located within and outside protected areas. So far the study has resulted in three peer reviewed publications and two presentations in international conference. Based on the findings of the study it could be inferred that the Travancore tortoise is sensitive to human disturbance. This might be the consequence of exploitation of the animal by the locals in the reserves where the study was conducted. It is not uncommon to find locals using domestic dogs during their forays into the forest. We speculate that there is some level of subsistence exploitation of the species in the region. The behaviour and ranging pattern of the species make them cryptic for detection by humans, but vulnerable to detection by domestic dogs. The study revealed that there is poor awareness among wildlife protection staff in the reserves on the species in general. Increasing the awareness of the staff could result in curbing subsistence exploitation of the species in the reserves. The vayals in the reserve are crucial habitats for the species; therefore, their protection and monitoring should be of importance for the persistence of the tortoise population. In the case the cane turtle, contrary to our initial expectations they survive in high densities (60 individuals in 1 sq. km) in the middle and low elevation evergreen forests (between 10 – 1000 m above mean sea level). The Karian Shola National Park is having a large population of this species which is of importance of the management of the protected area. The species is extremely stenotypic, showing strong preference to a narrow range of microclimatic variation prevailing in evergreen forests that are below 1000 m elevation in the Western Ghats. This indicates that the low elevation evergreen forest areas are crucial habitats for the species. Our intensive study on the species spanning over four years did not yield much information on the reproductive ecology of the species, because of their secretive lives. We recommend studies on the reproductive biology of the species, which might be important in the context of conservation breeding of the species. In the case of Leith’s softshell, we suggest extensive surveys to document the distribution, the status of population and, the genetic and morphological variation in the populations in peninsular India
Added by: Sarina Wunderlich |