Literaturdatenbank
Literaturdatenbank |
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Kavanagh, B. T. (2009). Sexual dimorphism, movement patterns, and diets of the razorback musk turtle (sternotherus carinatus) and community characteristics of turtle populations inhabiting two small streams of east texas. Unpublished thesis Masters, Stephen F. Austin State University.
Added by: Sarina Wunderlich (12 Dec 2010 20:43:07 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: Kavanagh2009 View all bibliographic details  |
Categories: General Keywords: Emydidae, Habitat = habitat, Kinosternidae, Nordamerika = North America, Schildkröten = turtles + tortoises, Sternotherus, Sternotherus carinatus, Trachemys, Trachemys scripta Creators: Kavanagh Publisher: Stephen F. Austin State University |
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| Abstract |
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This study was undertaken in order to simultaneously assess the influences of urbanization on two turtle communities of East Texas and the movement patterns of the razorback musk turtle (Sternotherus carinatus ). Additionally, patterns of sexual dimorphism were quantified and the evolutionary forces shaping S. carinatus morphology were examined using analyses of movement patterns and diets. La Nana Creek, a stream heavily influenced by the effects of urbanization, and Bernaldo Creek, a stream relatively unaltered by anthropogenic disturbances, were sampled for turtles in the spring and summer of 2007 and 2008. Machrochelys temminckii from Bernaldo Creek and Trachemys scripta from La Nana Creek had male-biased sex ratios. Mean curved carapace lengths reported for each sex did not indicate increased mortality rates on female turtles inhabiting La Nana Creek. The frequency of leech parasitism was quantified and no significant differences were found between the sexes of each species within each study site, but Sternotherus carinatus from Bernaldo Creek had significantly greater numbers of leeches than individuals from La Nana Creek. When data were pooled between study sites, aquatic turtles were significantly more heavily infested with leeches than basking turtles. Univariate and multivariate analyses indicate that the 28 live S. carinatus caught for this study display male-biased sexual dimorphism, a pattern which was partially corroborated by analyses performed on 39 preserved museum specimens. Twenty-three S. carinatus were caught and radio tracked throughout the course of this study. No significant differences were found between male and female home ranges, maximum distance moved, and total distance moved but females did have significantly higher mean daily speeds. Active season home ranges of female razorback turtles from La Nana were significantly greater than inactive season home ranges. Habitat comparisons conducted in fall 2009 revealed that Bernaldo Creek had significantly greater amounts of canopy cover and structural features. Sternotherus carinatus from both creeks were highly associated with structural features and areas greater than 50 percent canopy cover and individuals from La Nana Creek were highly associated with a sand/gravel substrate type. Male and female razorback musk turtles were found to feed on a similar variety of organisms in similar proportions and food items included freshwater mussels, crustaceans (crayfish), arthropods, and plant material. Analysis of the proportional use of food resources between males and females yielded a Simplified Morisita Index value of 0.764, indicating a high degree of food resource use overlap. Analysis of the proportional use of food resources between Bernaldo Creek and La Nana Creek turtles yielded a Simplified Morisita Index value of 0.163, indicating a low degree of food resource use overlap.
Added by: Sarina Wunderlich |