Literaturdatenbank
Literaturdatenbank |
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Vogt, R. C. , Use of satellite transmitters in determining habitat use of podocnemis expansa in the rio trombetas, para, brazil. Paper presented at Turtle Survival Alliance 2006 Annual Meeting.
Added by: Admin (13 Dec 2008 22:23:58 UTC) |
| Resource type: Proceedings Article BibTeX citation key: Vogt2006a View all bibliographic details  |
Categories: General Keywords: Habitat = habitat, Podocnemididae, Podocnemis, Podocnemis expansa, Schildkröten = turtles + tortoises, Südamerika = South America Creators: Vogt Collection: Turtle Survival Alliance 2006 Annual Meeting |
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| Abstract |
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Podocnemis expansa is listed as NR conservation dependent by the IUCN because of the continued effort Brazil has made towards the conservation of this species at the nesting beaches. This has worked in many areas where the nesting populations have increased or at least remained stable. This is not the case in the Trombetas River where populations have crashed from 8000 in 1976, to 850 in 1989, to less than 200 in 2003. IBAMA has requested that this population be listed as Critically Endangered because of the recent rapid decline. During 1989-1996, we were able to show through the use of VHF transmitters that the turtles nesting on the beaches in Trombetas River leave the reserve and the river after the nesting season, but we were not able to determine where they went. In November 2005 we attached both VHF and satellite transmitters to 10 post nesting females to determine where they migrate after the nesting season and to discover if the ships used in transporting bauxite may be frightening the turtles away from the river. In addition to this we wanted to find out where the turtles actually go when they leave the river and how long they remain in other habitats. The project is a success we are documenting the movements and microhabitat use by 8 of the tagged females. After 6 months the turtles are all still within the reserve, some have migrated 65 km downstream, others have taken up residence in the large lakes. Some have been found foraging in 1.5 m of water with temperatures of 43 C. The migratory route of each individual was tracked using satellite images. As of May 2006 we received 314 locations for 8 turtles as well as 1531 temperatures of the transmitters, indicating the temperature of the water they were in and thus the microhabitat. The 8 turtles were found to use a mean area of 210.65 km2. The total area occupied by the 8 turtles was 1582.00 km2. It would have been impossible to track 8 individual turtles using standard VHF transmitters these distances in this time frame. The mean straight line distance from first capture to final point was 22.70 km for each turtle. This under estimates their movements since the rivers and lakes that they entered meander considerably. The water temperature where they were located varied from 22.5 C to 47 C, mean of 29.9 C. There are some serious limitations as to what satellite transmitters can elucidate about this turtles habitat use and movements; however without satellite transmitters it would have been impossible to find these turtles in their foraging grounds. They go up very small tributaries within the flooded forest and forage in water 1.5-2 m deep. Locations are received only when the turtles happen to be in a clearing and at the surface for long at least 2.5 min. Even when we know where the turtle is by satellite location, it often takes 4-6 h paddling in small canoe to reach the area deep into the flooded forest where the VHF signal can be picked up. The limitations of satellite transmitters for tracking freshwater turtles will be discussed.
Added by: Admin |