Literaturdatenbank
Literaturdatenbank |
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White, L. C. (2009). Gopher tortoise (gopherus polyphemus) habitat selection, health, and fecundity. Unpublished thesis , University of Florida.
Added by: Sarina Wunderlich (18 Nov 2012 17:47:14 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: White2009 View all bibliographic details  |
Categories: General Keywords: Ernährung = nutrition, Fortpflanzung = reproduction, Gopherus, Gopherus polyphemus, Habitat = habitat, Nordamerika = North America, Schildkröten = turtles + tortoises, Testudinidae, Toxikologie = toxicology Creators: White Publisher: University of Florida |
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| Abstract |
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Testudinidae Habitat alterations that have resulted in a loss of diversity or abundance of plant species could potentially decrease the nutritional status of animals over time, thereby affecting their growth rates, survival, or reproduction. The overarching goal of this project was to examine whether alterations to gopher tortoise (Gopherus polyphemus) habitats could negatively impact their nutritional status or fecundity. To answer this question we examined (1) individual habitat selection to determine if gopher tortoises were selective in their use of resources when habitat type varied, (2) whether habitat parameters could be used to predict gopher tortoise nutritional status, and (3) the influence of nutritional status (determined by blood biochemistry and vitamin and mineral assays) on reproduction in gopher tortoises. Our results indicated that tortoises largely used broad vegetation categories (grasses, forbs, legumes, and woody species) in proportion to their availability. This finding could potentially have different consequences for tortoises in different sites or habitat types. For example, legumes are thought to be particularly important for re-conditioning females after egg laying, but if these items are less available in some habitats they may also constitute less of their diet. Interestingly, both clutch sizes and percent gravid females were lowest in this study at the site with lowest percent cover of legumes. We also found that the habitat measurements used in this study were not able to account for a significant amount of the variability in gopher tortoise blood parameters. However, there were significant main effects and interactions for site, year, and sex, for many of the gopher tortoise blood parameters, suggesting the importance of the reproductive cycle and geographic location on blood parameters in this species. Female gopher tortoises with lower body condition scores and lower plasma phosphorus levels were less likely to have eggs than females with lower body condition scores. Not unexpectedly, clutch size in gopher tortoises increased with carapace length. We also identified three minerals (zinc, manganese, and selenium) that differed significantly between gravid and non-gravid female gopher tortoises. Although the importance of these minerals to reproduction has been demonstrated in other species as we initially positied, more data are needed to determine whether levels in non-reproductive females truly represent deficiencies or toxicity in this species. Future studies will need to address the extended reproductive cycle of gopher tortoises as it may be difficult to determine a time of the year when blood parameters are not at least partially influenced by reproduction. Sampling blood parameters and forage availability at multiple times during the year may help address this problem as well as increase our understanding of whether nutrients acquired prior to or after brumation (period of inactivity when metabolism slows but animals are still awake) influence reproduction.
Added by: Sarina Wunderlich |