The Herpetological Journal

pp.57-64

Authors: L. Luiselli, G. C. Akani, E. Politano, E. Odegbune And O. Bello

Abstract: The diet of sympatric freshwater turtles was studied at two study areas in the Niger Delta (southern Nigeria), to test whether oil pollution affects the ecological relationships between free-ranging turtles. Two study areas, one unpolluted and one polluted by an oil spill, were used for our comparisons. Both areas had similar environmental conditions, i.e. a main river tract with banks covered by dense gallery forest, seasonal swamps in riverine forest, and almost permanent marshes with rich aquatic vegetation. Four species of turtle ( Trionyx triunguis, Pelusios castaneus, Pelusios niger, and Pelomedusa subrufa), were captured in the unpolluted area, whereas only two species (Pelusios castaneus and Pelusios niger) were captured in the polluted area. At the unpolluted area, the taxonomic composition of the diets of Pelusios castaneus and Pelusios niger was similar, whereas the diets of Pelomedusa subrufa and Trionyx triunguis were very different from the other two species and one another. In the polluted area, the taxonomic composition of the diet of Pelusios castaneus was significantly different from that of conspecifics in the unpolluted area, and consisted mainly of plant matter, annelids (earthworms and leeches), and gastropods. The taxonomic composition of the diet of Pelusios niger was also significantly different from that of conspecifics at the unpolluted area, and consisted mainly of annelids and gastropods, and secondarily of plant matter. Amphibian prey (eggs, tadpoles, and adults), which were one of the main food types for all turtles in the unpolluted area, practically disappeared from the diet of turtles at the polluted area. It was evident from this study that the two species that survived the oil spill event shifted considerably in their dietary preferences. In particular, in both species there was an obvious trend towards a reduction in the breadth of the trophic niche, with many fewer food categories eaten at the polluted area compared to the unpolluted area. It is suggested that such reduction in trophic niche breadth may depend directly on the reduced availability of most food sources (particularly amphibians, fish, and environmentally-sensitive invertebrates) in the polluted area, despite over 10 years having elapsed since the spill, and restoration operations at the site. It is likely that the above-mentioned reduction in trophic niche breadth also depended on the shifts in habitat use by the surviving turtles, which tended to concentrate into single habitat types in the polluted area, compared to the unpolluted area where they were more habitat generalists.

Keywords: Chelonia, community ecology, feeding ecology, pollution, resource partitioning

pp.65-77

Authors: Anita Malhotra , Roger S. Thorpe And Bryan L. Stuart

Abstract: Morphological similarity has created considerable taxonomic uncertainty among the Asian green pitvipers. A new species of green pitviper, Trimeresurus vogeli, was recently described from Thailand. T. vogeli represents a distinct phylogenetic clade within the Trimeresurus stejnegeri group and is morphologically different from other clades of the T. stejnegeri group in several respects. However, the only obvious consistent difference between T. vogeli and other clades of T. stejnegeri is its lack of a red tail. Here, we perform a morphometric analysis to compare T. vogeli to other species with which it may be confused. Our data on T. vogeli differs in many respects to those presented in the species description, including characters considered diagnostic. In the past, T. vogeli has frequently been mistakenly identified as Trimeresurus popeiorum, from which it can be distinguished by the hemipenis structure in males. The tail colour characteristic is not reliable in distinguishing T. vogeli from all populations of T. popeiorum, and we review the morphological differences between these and T. vogeli females. We report a range extension to Cambodia, Laos and Vietnam, and provide habitat data for the species. The range of T. vogeli does not overlap with that of T. popeiorum or other members of the T. stejnegeri group.

Keywords: green pitviper, SE Asia, taxonomy, Viperidae

pp.79-87

Authors: Akira Mori And Gordon M. Burghardt

Abstract: The effects of temperature on the antipredator responses of snakes have been extensively studied during the last two decades. Several contradictory results have accumulated concerning the effects of temperature on the propensity of snakes to perform various behaviour patterns. We review this literature and discuss four possible factors related to these apparently contradictory results: (I) inconsistency in terms used to characterize antipredator behaviour; (2) erroneous citations; (3) interspecific differences; and (4) variable experimental designs. The last two factors reflect biologically important phenomena, whereas the first two are artificial "noise" that causes confusion and hinders scientific interpretation. To resolve inconsistency in wording, we propose a consistent terminology for the antipredator responses of snakes. Antipredator responses were characterized from three dimensions: (I) categorization from the viewpoint of whether prey animals move towards or away from predators (response is considered as either "approach", "neutral", or "withdrawal"); (2) categorization from the viewpoint of how much movement is involved in the behaviour (response is considered either "locomotive", "active-inplace'', or "static"); and (3) categorization in terms of the apparent function (response is characterized as either "threatening'', "cryptic", or "escape"). Anti predator responses of snakes, not only in relation to temperature but also in any situation, can be well characterized from these three perspectives using the proposed terminology.

Keywords: defences, predator-prey interaction, reptile, temperature effect

pp.89-97

Authors: Marc Sztatecsny, Robert Jehle, B Enedikt R. Schmidt And J. W. Arntzen

Abstract: Despite the key role of premetamorphic amphibians in experimental ecology, the factors affecting their abundance has received relatively little attention in natural settings. We applied a model selection approach with AIC (Akaike's Information Criterion) to predict the abundance of embryos and larvae of crested and marbled newts (Triturus cristatus and T. marmoratus) at 32 breeding sites in western France, based on 15 variables describing the aquatic habitat, and 10 variables describing the terrestrial habitat within a 100 m radius around the pond. The best model for embryos included the variables shade and floating vegetation (highest embryo abundance in intermediate ponds), and pond size (negative correlation). Larval abundance was best explained by shade (negative correlation), and the interaction between phosphate and nitrate. Pond variables were not fully comparable to terrestrial parameters, but produced better predictive models for both embryos and larvae. Due to the high explanatory value of ecological parameters the results suggest that in a metapopulation context, deterministic population processes driven by pond succession may be more important than stochastic extinctions and recolonizations of otherwise suitable habitat patches.

Keywords: AIC, ecological determinants, habitat selection, Urodela

pp.99-107

Authors: Claudio Ciofi And Muriel E. De Boer

Abstract: Information on population size and distribution of the Komodo monitor (Varanus komodoensis) has so far been restricted to early reports or to surveys conducted on only part of the species' range. We carried out a study based on transects through sampling plots and single-catch trapping events to assess the extent to which the distribution of V. komodoensis has changed since the last comprehensive survey was conducted, in 1 971. We also report on the status of the habitat and identify conservation priorities. Resident Komodo monitor populations are now found on only four islands in Komodo National Park and on the island of Flores in south-east Indonesia. Average population density estimates recorded on Flores were more than 60% lower than those reported for Komodo National Park. Habitat fragmentation and poaching of prey species currently represent the main threats to the Komodo monitor, and protection of monsoon forest in west and north Flores is crucial for the long-term conservation of the species.

Keywords: geographical distribution, lizard conservation, population density estimates, Varanid

pp.109-112

Authors: DAVOR VRCIBRADIC , MÔNICA CUNHA-BARROS AND CARLOS FREDERICO D. ROCHA