Literaturdatenbank
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Davies, C.-L. (2005). Thermoregulation, activity and energetics of the pig-nosed turtle (carettochelys insculpta) in the daly river, northern territory. Unpublished thesis , University of Canberra.
Added by: Admin (06 Jan 2014 18:22:44 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: anon2005a View all bibliographic details  |
Categories: General Keywords: Australien - Australia, Carettochelyidae, Carettochelys insculpta, Ernährung - nutrition, Habitat - habitat, Physiologie - physiology, Schildkröten - turtles + tortoises, Verhalten - ethology Creators: Davies Publisher: University of Canberra |
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| Abstract |
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The thermoregulation, activity and energetics of 24 pig-nosed turtles (Carettochelys insculpta) in the Daly River was studied in the dry season of 2004. For this research I used a combination of traditional and novel techniques, including radiotelemetry and isotope dilution, surgically implanted miniature temperature dataloggers and a recently developed activity datalogger. Thermal data revealed that C. insculpta used thermal springs extensively during the tropical dry season. Most turtles used thermal springs every day, and in doing so they significantly raised their internal body temperature (Tb). This indicates that thermoregulation is important for C. insculpta in the study area. Females maintained a differential between river water temperature (Tw) and (Tb) approximately 0.5ºC higher than males, however there was no significant difference in the temperature differential between non-gravid females and gravid females. I suggest that the primary role of thermoregulation in this population is to maximise energy intake. By repeatedly basking animals are be able to maintain Tb within their activity range, enabling them to be active and therefore feed both day and night. This thermoregulation would also optimise digestive efficiency at the physiological level. The difference between thermoregulation in males and females may reflect the difference in energy invested in reproduction by the sexes. Activity data showed that females are not nocturnal as has been previously suggested and in fact they are active day and night, including several periods of high activity over a 24-hour period. These periods are usually interspersed with periods of low activity and high Tb suggesting that during these periods of low activity animals are basking on thermal springs. By utilising this unusual heat source they can be active regardless of time of day. This continuous cycle of activity and thermoregulation by thermal spring basking also suggests that the animals may be attempting to maximise food intake. Total body water (TBW) in all animals was quite high, suggesting that these animals are lean, and there were no notable decreases in TBW over the study period indicating that animals were not depositing fat as a means of energy storage. Results indicate that energy intake in these animals is very low (based on calculations from other turtle species) and it is unlikely that energy intake is high enough to satisfy requirements of field metabolic rate. Collectively, the findings of this study support the notion that Australia’s largest known population of C. insculpta is energy-limited. Proposed agricultural development and subsequent water extraction in the Daly River Catchment has the potential for significant negative impacts on the species under a variety of flow regimes, particularly in regard to access to ribbonweed (their primary dry-season food source). If this population is energy-limited, then such impacts could exacerbate energy uptake problems, resulting in a reduction in reproductive output, and therefore a potential population decline. Pig-nosed turtles are listed internationally as vulnerable on the IUCN threatened species red list, and have recently been nominated for listing as vulnerable at a federal level; consequently the results of this study are important for this species’ conservation.
Added by: Admin |