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    Aspects of the osmotic and water balance of the New Zealand native frog Leiopelma hochstetteri fitzinger, and the Australian whistling frog Litoria ewingi dumeril and bibron : a thesis ... for the degree of Master of Science in Zoology
    (Massey University, 1974) Cameron, Murray Colin
    Rates of dehydration and rates of water uptake when hydrated or dehydrated are described for two species of frogs of similar size from different habitats. No detectable differences in rates of water loss in frogs of both species of comparable size were noted. Considerable differences were seen in rates of water uptake. These uptake rates were lower in hydrated and dehydrated Le. hochstetteri than in hydrated Li. ewingi. Differences in rates of water uptake were reflected in measurements of skin permeability and blood plasma osmolality. Rates of water uptake in Li. ewingi were dramatically increased after dehydration, and it was proposed that this was due to hormonal mediation. The osmotic permeability of different skin regions in frogs of different species may vary in the presence or absence of oxytocin or vasopressin. This was not observed in Le. hochstetteri where the skin exhibited relatively uniform permeability, but was seen in Li. ewingi and Li. aurea. In these two species, the abdominal skin was more permeable and more readily stimulated by oxytocin or vasopressin than the dorsal skin. Oxytocin and vasopressin also increased the short circuit current (inward Na+transport) through both dorsal and ventral skin in Le. hochstetteri, but most noticeably through the ventral skin in Li. ewingi and Li. aurea. The skin was observed to be thinner in Li. ewingi than in Le. hochstetteri or Li. aurea. Thin areas in the ventral pelvic integument of Li. ewingi and Li. aurea and the presence of epidermal capillaries in these two species are thought to be of importance in water uptake. It has been suggested that water uptake mechanisms are a major factor determining the distribution of the three frog species.
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    Conservation issues for Hochstetter's frog (Leiopelma hochstetteri): monitoring techniques and chytridiomycosis prevalence in the Auckland region, New Zealand : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Auckland, New Zealand
    (Massey University, 2009) Puig, Virginia Moreno
    Amphibians are suffering extinctions and range contractions globally. This is caused by numerous factors and most of them are related to human activities. The overall aim of this thesis was to make a significant contribution to the conservation of the endemic amphibian Leiopelma hochstetteri through research. This was achieved by focusing in two of the main conservation issues for this species, the need for standardised and robust monitoring techniques to detect trends and changes in populations, and the determination of the prevalence of chytridiomycosis, caused by the amphibian chytrid fungus (Batrachochytrium dendrobatidis). Two populations of the Auckland Region were selected for this study, one on the mainland (Waitakere Ranges) and the only known offshore island population of this species (Great Barrier Island). For both study sites different monitoring methods were used to obtain some population parameters. Site occupancy models of MacKenzie et al. (2002) gave reliable site-specific estimations of occupancy and detection probability using covariate information and presence-absence data collected from 50 sites in the Waitakere Ranges and four repeated visits during 2008. Elevation and distance searched were found to have an important effect on occupancy levels, while time taken to search the site was important variable determining detection probabilities. Also, parameters were estimated for three age classes separately. Statistical models were used to infer abundance from occupancy analysis, and results were compared with the distribution of relative abundances obtained from repeated transect counts and an established sight/re-sight criterion. In addition, the use of surrogate measures for relative abundance was explored. Detection probability and the distance to first frog found were found to have a significant correlation with relative abundance. These measures can be used to infer relative abundance in future site occupancy surveys. Two surveys and a pilot site occupancy survey were conducted on Great Barrier Island, and presence of frogs was confirmed atthe northern block, and in a small seepage in the central block. No new locations were found. Waitakere Ranges and Great Barrier Is. populations were tested for the presence of chytridiomycosis, and all frogs sampled tested negative (n = 124) which means that if present chytridiomycosis prevalence is lower than 5% with a 95% confidence interval. This and previous evidence suggests that L. hochstetteri may be resistant or immune to the disease. However, to confirm this additional studies are needed.