Zoology - Theses

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Start date: 1962 × End date: 1979 × Subject: reproduction ×

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    Life-history strategies of five species of intertidal limpet
    Parry, Gregory Douglas ( 1977)
    The life-long strategies of five species of intertidal limpet, Cellana tramoserica, Notoacmea petterdi, Patella peroni, Patelloida alticostata, and Siphonaria diemenensis, which occur on the same shore but in different tidal zones, are considered in relation to their different environments. Attention is focused upon reproductive effort, which is defined as the percentage of assimilated energy devoted to reproduction, and which is measured for each species by using annual energy budgets. Environmental and demographic factors, which previous workers have suggested may have important influences on the level of reproductive effort, are investigated. In particular, interspecific differences in reproductive effort are compared with differences in the availability of food resources, differences in the magnitude of density-independent causes of mortality, differences in adult mortality rates and differences in extrinsic adult mortality rates (i.e. the adult mortality rates that would occur in the absence of expenditure of energy in reproduction.) The results of the present study indicate that reproductive effort is correlated with the availability of food resources, but that the primary determinant of the optimum level of reproductive effort is the rate of extrinsic adult mortality.
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    Ecological and physiological studies of Sminthopsis crassicaudata (Marsupialia : Dasyuridae)
    Morton, Stephen Ross ( 1976)
    This study aimed to identify the major adaptations enabling a small insectivorous marsupial, Sminthopsis crassicaudata, to inhabit a variety of open grassland and desert environments. A series of integrated investigations of behaviour, reproduction and physiological ecology was carried out. S. crassicaudata displays a "drifting home range" pattern of social organization, there is little evidence of territorial behaviour, and individuals are solitary during breeding but gregarious in autumn and winter. In both arid and comparatively mesic habitats, breeding occurs from late winter until early autumn; there is no evidence that opportunistic breeding takes place in late autumn or early winter. During the breeding season each female attempts to raise two litters; few individuals of either sex breed in more than one season. All these characteristics are interpreted as adaptations to both long-term (seasonal) and short-term variability in food supply. S. crassicaudata can survive without drinking water when fed on a diet of insects. This independence is made possible by the high water content of the food, and not by physiological restriction of water loss as is seen in granivorous desert-dwelling rodents. Similarly, the energy metabolism of S. crassicaudata shows no evidence of specific adaptations to aridity. The apparent physiological specializations - brief diurnal torpor and fat storage - seem to be related to the problem of fluctuation in food supply, and not to aridity as such. Thus the biology of S. crassicaudata is interpreted as reflecting specific adaptation to variability in food supply; this variability seems to be the major problem facing a nocturnal insectivore inhabiting open environments.