Literaturdatenbank
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Arsenault, L. M. (2011). Headstarting blanding’s turtles (emydoidea blandingii) in nova scotia: an investigation of artificial incubation, captive-rearing, and release to natural habitats. Unpublished thesis , Acadia University.
Added by: Sarina Wunderlich (18 Nov 2012 17:43:03 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: Arsenault2011 View all bibliographic details  |
Categories: General Keywords: Schildkröten = turtles + tortoises, Zeitigung = incubation Creators: Arsenault Publisher: Acadia University |
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| Abstract |
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Post-release survival, growth, and movement patterns The research presented here suggests that post-release survival of headstarted juvenile Blanding’s turtles in Nova Scotia may be similar to that of same-aged wild juveniles and hatchlings. The survival of headstarted juveniles up to 2 years following release suggests they have the ability to adapt to release environments and avoid predation. However, further investigation is warranted because of this study’s small sample size. The present study suggests that headstarted and wild juveniles differ in their size-age relationship. At release, headstarted juveniles were larger than wild juveniles of the same age and appear to remain larger throughout the juvenile stage. Relative instantaneous growth rates of headstarted and wild juveniles were similar. These results suggest that headstarted juveniles may be able to acquire and process resources similarly to wild juveniles of the same size. Because the onset of sexual maturity is thought to be related to size and not age, headstarted juveniles may reach sexual maturity at a younger age than wild juveniles. However, extended sampling is required to better understand the implications of headstarting on the onset of sexual maturity. The present study also recorded similar displacement and movement rate in headstarted and wild juveniles. These findings suggest that headstarted and wild juveniles may use habitat similarly. Other studies have suggested that headstarted juveniles may travel greater distances or wander aimlessly following release in contrast to wild juveniles (Hester et al. 2008; Okuyama et al. 2010). These differences in movement patterns may be associated with unfamiliarity of the release environment, an attempt to find suitable habitat, or an attempt to return to the original site (Hester et al. 2008). However, in this study, headstarted juveniles may not have needed to make longer movements because they had been released to suitable habitats. Survival of headstarted juveniles to subadult age and similarities in growth and movement patterns with wild juveniles of comparable size provide evidence for the success of this headstarting program. These findings suggest that headstarted juveniles were able to adapt to their new environment and display behaviours similar to those of wild juveniles. However, the post-release analysis presented here is not sufficient to determine the success of the headstarting program for Blanding’s turtles in Nova Scotia. The ultimate goal of headstarting is to increase juvenile recruitment; however, this can only be assessed once headstarts reach sexual maturity. Artificial incubation: effects of incubation temperature All temperature treatments examined here (27.0, 28.0, and 28.5 0.4°C; 28.5, 29.0, 29.5, and 30.0 0.7°C) yielded high hatching success and high post-hatching survival. Therefore, these incubation environments appear suitable for headstarting Blanding’s turtles in Nova Scotia. The research presented here supports findings of near constant temperature being inversely related to incubation duration and suggests temperature fluctuation of 0.7°C may mask such effects. This suggests that temperature fluctuation may decrease incubation duration at a mean incubation temperature of 28.5°C for Blanding’s turtle in Nova Scotia. Temperature fluctuation may also decrease hatchling size at a mean incubation temperature of 28.5°C for Blanding’s turtle in Nova Scotia. However, this temperature-induced variation in hatchling size disappeared at 12 months of age for carapace length and 2 months of age for mass. The research presented here supports findings of near constant temperature being inversely related to hatchling size with larger hatchlings produced at cooler temperatures. This research suggests temperature fluctuation of 0.7°C may mask such effects. At near constant incubation temperature, mean temperature may influence hatchling size during their first year. However, mean temperature does not appear to affect hatchling size at 19 months of age. Headstarting programs typically grow turtles in captivity for at least 1 year with a 2 year period in this study. Therefore, the effects of mean and fluctuating temperature observed here may not have important implications for size at release. For the temperature regimes presented here, clutch may account for a greater proportion of the variance in size at release than does incubation temperature. Larger hatchling size may reduce the risk of predation and increase fitness (Janzen et al. 2000). Therefore, findings presented here suggest clutch may have a greater effect on hatchling fitness at release than does incubation temperature regime. However, greater temperature fluctuations may affect post-hatching growth and size at release. Because temperatures fluctuate in natural nests, a better understanding of its effects on developing embryos is needed. This may be achieved by examining the effect of accumulated heat or degree days above a threshold temperature for development. Further research should examine the effects of temperature fluctuation on other fitness related traits of hatchlings such as righting time and immune response. This thesis contributes to the better understanding of the effectiveness of headstarting programs and provides valuable information for the conservation of turtle species.
Added by: Sarina Wunderlich |