Literaturdatenbank
Literaturdatenbank |
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Mosimann, D. (2003). Ökologische untersuchungen an einer population der europäischen sumpfschildkröte emys orbicularis (linnaeus, 1758) 50 jahre nach der ersten (wieder-) ansiedlung in moulin-de-vert (genf, schweiz). Emys, 10(3), 4–16.
Added by: Admin (14 Aug 2008 20:36:25 UTC) Last edited by: Beate Pfau (18 Oct 2009 18:38:04 UTC) |
| Resource type: Journal Article BibTeX citation key: Mosimann2003a View all bibliographic details  |
Categories: General Keywords: Emydidae, Emys, Emys orbicularis, Europa = Europe, Habitat = habitat, invasive Arten = invasive species, Pseudemys, Schildkröten = turtles + tortoises, Trachemys, Trachemys scripta Creators: Mosimann Collection: Emys |
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| Abstract |
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Emys orbicularis Pseudemys Trachemys scripta This paper is a summary of my study on a wild population of the European Pond turtle, Emys orbicularis (LINNAEUS 1758) in the south-west of Switzerland. The goal of my diploma work was to establish a census of the population of Emys orbicularis in the Moulin-de-Vert reserve, in the canton of Geneva (Switzerland), 50 years after the introduction of the first individuals, and to gather informations on their use of habitat struchtures. The study is based on three principal methods: direct visual observations, capture-marking-recapture and nesting observations. • Visual observations: 1439 observations were recorded between April 11, 2001 and October 19, 2001 in this reserve. The climatic data which are most significant for the observations are the duration and intensity of sunshine. At the time of this study almost all observations were on the European Pond turtle (less than 5% of the observations were on Trachemys scripta elegans). All age groups of turtles could be observed, but most observations were on adults. It seems however that the real number of the other age groups is greater than observed, perhaps because the younger animals are shyer and more cryptic (for example to aviod predators) which could lead to an underestimation of their population. The adult sex-ratio is skewed in favour of females (1M:1,47F). The activity mainly observed is basking. This result was expected in such small and oblong ponds which provided excellent sight. Deadwood is the preferred basking site (nearly three-quarter of the observations). Reed is of secondary importance as basking site. Red-eared sliders mostly occupy those basking sites that are not preferred by the European Pond turtles. • Capture-Mark-Recapture method I used the trapping method developed by CADI et al. (in press). The great efficiency of this method was proved during the experiment. I trapped 462 turtles in four sessions, which represented a total of 260 different individuals. The number of new individuals caught decreased decreasing significantly in of the second and following sessions. Only 6 individuals of Trachemys scripta elegans were captured, confirming their low number in the Moulin-de-Vert reserve. Most European Pond turtles were captured several times. The highest trapping efficiency was in summer. During the pre-nesting trapping session (mid-may 2001), males were most abundant, proving their high activity level in the period of reproduction. In the following sessions females were more abundant than males. Subadults and juveniles were captured in greater number from the beginning of summer until end of september. The adult sex-ratio was in favour of the females (1M:1,47F). I estimate the adult population size to 306 ± 10,5 (berechnet mit der Software Capture 2©). This represents a density of 64 individuals/ha. My data indicate thatthe growth of the European Pond turtle is exponential and very fast, the males reaching maturity in about five years and the females in six to eight years. Carapace length of adult males was 133,6 ± 8,2 mm (109 - 154 mm),and weight was 344,3 ± 52,0 g (235 - 480 g). Carapace length of adult females is 149,3 ± 11,9 mm (114 - 175 mm), and weight is 557,7 ± 139,3 g (255 - 935 g). One third of the animals moved at least once to another pond, implying a minimal distance from 10 to 140 meters, probably during one night. A great number of Emys orbicularis in the reserve had deformations of the scutes. • Nesting observations The third method was the observation of nestings sites. Only fifteen nests were discovered and only two of them hatched, the others having been predated mainly by wild boars and badgers. The cultivated fields near Hainard Pond appeared to be nesting zones for Pond turtles too, but agricultural cultvation reduced the hatching success of the eggs deposited there. The survival of the population depends on hatchling survival, which seemed rather low at the time of the study. Therefore an improvement of the nesting zones should be considered. This study allowed me to understand the climatic and environmental conditions necessary for the survival of the European Pond turtle in Switzerland. I could show that they are sufficient or natural reproduction. This information implies that the establishment of naturally reproducing poupulations of the European Pond turtle is possible in the lowlands in the south-west of the country. Added by: Admin Last edited by: Beate Pfau |