Papers by Gerald Kuchling
Endangered Species Research, Sep 17, 2020
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Journal of Sea Research, 2019
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Australian Journal of Zoology, 2014
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Biological Conservation, Dec 1, 2016
Abstract The embryos of many egg-laying species develop under the environmental conditions select... more Abstract The embryos of many egg-laying species develop under the environmental conditions selected by one or both parents, and these conditions may cease to be optimal under a changed climate. Assisted colonization is an emerging option to relocate species that are threatened by unfavourable changes in the local climate, but the incubation requirements of embryos are rarely considered in conservation translocations despite suggestions that relocation of early life stages could be more effective than relocating older animals. Here we review examples and outcomes of relocations of reptile eggs, and the decision tools currently available for guiding translocation decisions from an embryonic perspective. We then demonstrate a mechanistic approach, using the modelling framework NicheMapR, for assessing the optimal translocation range for the Western Swamp Turtle ( Pseudemydura umbrina ), a Critically Endangered reptile with an extremely restricted natural distribution. We determine thermal reaction norms and critical thermal limits for embryonic development based on laboratory and field data, and model soil temperatures at typical nest depths, simulate embryonic development at these depths, and map the probability of survival of P. umbrina embryos within the major bioregions of south-western Australia. The same model forced by future climates for 2050–70 demonstrates a southerly shift in the regions where embryos would be viable. However, if P. umbrina is to be translocated in the near future to regions 300–400 km south of its natural range, females will need to nest in relatively unshaded sites to achieve temperatures that are high enough to promote hatchling success.
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Chelonian Conservation and Biology, 1995
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Endangered Species Research, Apr 12, 2012
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Chelonian Conservation and Biology, Jun 1, 2012
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Springer eBooks, 1999
The anatomical, histological, endocrinological, physiological and behavioural methods used to stu... more The anatomical, histological, endocrinological, physiological and behavioural methods used to study reproduction of chelonians are principally the same as for other vertebrates. The box-like armour of chelonians, however, makes access to reproductive organs more difficult than in most other groups. Hurdles to reproductive biological investigations include difficulties in finding animals (or certain life stages) on a regular basis over the whole year, difficulties in readily assessing reproductive conditions in live animals (some species are even difficult to sex externally) and difficulties in obtaining blood or tissue samples. Reviews and comprehensive descriptions of general techniques for chelonian life history studies (including collecting, trapping, tracking, marking techniques, measurements and stomach flushing for dietary analyses) can be found in Gibbons (1990b), Graham (1979) and Wilbur and Morin (1988); details are beyond the scope of this book and are not presented here. Beyond the scope of this book also is the description of reproductive physiological laboratory techniques. This account deals primarily with methods to obtain reproductive biological data during field investigations.
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Springer eBooks, 1999
In all organisms, reproduction is timed through natural selection to occur during those periods o... more In all organisms, reproduction is timed through natural selection to occur during those periods of the year that are most propitious for the survival of both parent and young. According to Baker (1938), these favourable conditions are the “ultimate cause” of a particular breeding season; the “proximate causes” which are another set of factors, initiate the sexual cycles at the appropriate time of the year (see Chap. 6). In the following account I will firstly discuss cycles according to the climatic zones, then discuss multi-year cycles and then some special adaptations to unpredictable or extreme environments. The focus of this chapter is on gonadal, mating and nesting cycles, and their timing.
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Amphibia-reptilia, 1981
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Amphibia-reptilia, 1981
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International Zoo Yearbook, 1988
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Chelonian Conservation and Biology, 2006
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General and Comparative Endocrinology, Jun 1, 1981
Abstract Males of the tortoise Testudo h. hermanni of a natural population in Montenegro, Yugosla... more Abstract Males of the tortoise Testudo h. hermanni of a natural population in Montenegro, Yugoslavia, and captive ones in an outside area in Vienna, Austria, were used for a comparative investigation. Throughout the year testis and epididymis were examined histologically and the activity of β- N -acetylglucosaminidase in these organs was determined biochemically and histochemically. The activity of this enzyme increased in the testis and epididymis with the appearance of differentiated spermatozoa during summer. In the epithelium of the ductuli epididymides there were segments with very high and others with very low activity of this enzyme at that time. In the testis only moderate activity of 3β-hydroxysteroid dehydrogenase was found from January to June in the Leydig cells and at any time of the year in the Sertoli cells. The concentration of testosterone in blood plasma was maximal during summer, the main period of spermiogenesis, minimal during winter, and between these levels in spring, during the main mating period. The high concentration of plasma testosterone in summer may have been necessary for the activation of β- N -acetylglucosaminidase in the ductuli epididymides at the time of the passage of spermatozoa.
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Journal of Zoology, Mar 1, 1993
The reproductive organs of logn‐term captive females and of wild females of the western swamp tor... more The reproductive organs of logn‐term captive females and of wild females of the western swamp tortoise, Pseudemydura umbrina, which were taken temporarily into captivity, were studied over several years by ultra‐sound scanning. Pseudemydura umbrina, a critically‐endangered species, is active during winter and spring when the ephemeral swamps it inhabits contain water and aestivates during summer and autumn (November to May/June) when the swamps are dry. The vitellogenic growth of ovarian follicles commences during aestivation in summer and continues during autumn and winter. The timing of the vitellogenic cycle is remarkably similar to that of many other Australian chelids and that of many other chelonians of temperate and subtropical regions, but the patterns of energy harvest, storage and allocation to ovarian follicles is different. Ovulation occurs between late September and early November and is preceded by a feeding bout and a sharp increase in female body mass. One clutch of 3–5 eggs (exceptionally of one or two) is laid in November/December. Sub‐adult females show cycles of follicular growth, followed by atresia, for several years before ovulating and laying eggs. Females taken into captivity may miss the following vitelogenic cycle, but captivity does not generally affect vitellogenic cycles. Ovulation and egg production of captive animals is easily suppressed, however, under stress or sub‐optimal food intake in spring. The sensitivity of ovulation to sub‐optimal conditions and the subsequent reabsorption of the yolk material may enhance survival of the reproducing individual during long dry periods in an unpredictable environment.
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Zoophysiology, 1999
... The reproductive biology of the chelonia. Post a Comment. CONTRIBUTORS: Author: Kuchling, G. ... more ... The reproductive biology of the chelonia. Post a Comment. CONTRIBUTORS: Author: Kuchling, G. PUBLISHER: Springer (Berlin and New York). SERIES TITLE: YEAR: 1999. PUB TYPE: Book (ISBN 3540630139 ). VOLUME/EDITION: Volume 38. PAGES (INTRO/BODY): xi, 223 ...
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Springer eBooks, 1999
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Zoophysiology, 1999
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Springer eBooks, 1999
The major threats to the persistence of chelonian species around the world are over-exploitation ... more The major threats to the persistence of chelonian species around the world are over-exploitation by humans, habitat loss and environmental degradation. That exploitation for food can extirpate chelonians was already convincingly demonstrated as early as the eighteenth century, when six out of eight species of giant tortoises on Indian Ocean islands were slaughtered and eaten until extinct (one more followed in the nineteenth century). Today, the IUCN-SSC (the World Conservation Union Species Survival Commission) classifies 38% of the world’s chelonians as threatened: 4% as critically endangered, 11% as endangered and 23% as vulnerable. Chelonians, thus, contain a much higher percentage of threatened taxa than birds and mammals, of which, respectively, 11 and 25% are threatened (Baillie 1996).
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Papers by Gerald Kuchling