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Accueil du site → Doctorat → Australie → 1996 → The foraging behaviour of the arid zone herbivores the red kangaroo (Macropus rufus) and the sheep (Ovis aries) and its role in their competitive interaction, population dynamics and life-history strategies

University of New South Wales (1996)

The foraging behaviour of the arid zone herbivores the red kangaroo (Macropus rufus) and the sheep (Ovis aries) and its role in their competitive interaction, population dynamics and life-history strategies

McLeod, Steven

Titre : The foraging behaviour of the arid zone herbivores the red kangaroo (Macropus rufus) and the sheep (Ovis aries) and its role in their competitive interaction, population dynamics and life-history strategies

Auteur : McLeod, Steven.

Université de soutenance : University of New South Wales

Grade : Doctor of Philosophy (Ph. D.) 1996

Résumé
The foraging behaviours of the arid zone herbivores the red kangaroo (Macropus rufus) and the sheep (Ovis aries) were studied over a four year period in western New South Wales. The effects of temporal variation in food or energy intake on the biology of these herbivores was examined. At most times sheep and red kangaroos have a high level of food overlap. I used a controlled removal experiment to test the hypothesis that these herbivores compete. In the experiment there were three treatments (x2 replicates) ; sheep only, red kangaroos only, and sheep plus red kangaroos. The productivity of the herbivores in the presence and absence of its putative competitor were compared to determine competitive effects. The results indicated that competition did not occur during the study. I also solved a mechanistic model of exploitative competition between these herbivores. The results of the model corroborated the results of the experiment. I conclude that exploitative competition between sheep and red kangaroos rarely occurs in the arid shrublands of western New South Wales. In this environment sheep and red kangaroos face wide temporal variations in food quantity and quality, which may have important consequences for their fitness. I used an optimal foraging model to test hypotheses that sheep and red kangaroos could select diets that maximised their fitness. The results indicated that the main feeding goal of these herbivores was energy maximisation. In addition, I used the optimal foraging model to examine the evolution of body size and sexual dimorphism in red kangaroos. The results indicate that the evolution of body size was constrained by energy intake. Also, sexual dimorphism may have evolved to maximise the fitness of red kangaroos under conditions of varying food availability. Finally, I simulated the population dynamics of red kangaroos to examine the utility of the concept of carrying capacity. The results suggest that the concept is not useful for predicting sustainable herbivore densities in highly variable environments, such as the Australian arid zone. The results suggest that measurements of food or energy intake can explain the population dynamics and life-history strategies of herbivores in variable environments.

Mots clés : Red kangaroo Behavior • Sheep Behavior • Kangaroo management • Arid regions ecology

Présentation (National Library of Australia)

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