thesis submitted to the School of Animal, Plant and Environmental Sciences, Faculty of Science, U... more thesis submitted to the School of Animal, Plant and Environmental Sciences, Faculty of Science, University of the Witwatersrand, Johannesburg in fulfillment of the requirements for the degree of Masters in Science. Johannesburg 2016.
Carnivores that exhibit fission-fusion social organization can adapt group sizes to prevailing so... more Carnivores that exhibit fission-fusion social organization can adapt group sizes to prevailing social and ecological conditions. This study focuses on social organization of African lions (Panthera leo) in the Okavango Delta, a seasonally flooded wetland. We used generalized estimating equations and generalized linear mixed models to estimate the effects of flooding, as well as prey availability and intraspecific competition on group sizes of lions. During years of high flood, total lion pride sizes as well as reproductive rates declined. Prides showed extensive overlap in annual home ranges, likely as a result of habitat saturation at high densities, and pride sizes were not limited by prey availability. At the subgroup level, the number of attending cubs was the most consistent predictor of subgroup size of adult females. For subgroups without cubs, higher numbers of neighbors in adjacent, competing prides resulted in larger subgroups in focal prides, likely to maintain numerical advantage in inter-pride encounters. Larger subgroups were also formed in response to greater availability of large prey, as successfully hunting large prey requires a greater degree of cooperation. In the southwestern Okavango Delta, competition for space resulting from changing flooding regimes is a greater limiting factor for total pride sizes than food availability.
Mating systems in animal societies contain both social and genetic components. Deviations between... more Mating systems in animal societies contain both social and genetic components. Deviations between these components may have important ramifications for our understanding of the evolution of animal reproductive strategies and their ecological correlates. However, although there is ample evidence for discrepancies between genetically assigned paternities and social associations in birds, relatively few studies have documented such differences in mammals. Moreover, few studies have addressed how deviations between social mating associations and actual mating activities influence patterns of resource utilisation in males and females. The aardwolf is a socially monogamous hyaenid that exhibits polygamous mating behaviour. Suitable den sites for resting and rearing offspring is an important resource for terrestrial mammals, and dens are vital to aardwolves as thermal refugia for protection of offspring. We show that temporal patterns in aardwolf den use relates to predictions from polygamous mating rather than social monogamy. Male aardwolves used more dens, changed dens more frequently and stayed in dens for shorter periods of time than females during both wet and dry seasons. We suggest that lower male den fidelity is either caused by males trying to maximize female encounters and to monitor female activity, or that it had evolved as a non-adaptive behaviour related to elevated androgen levels. Our data did not point to territorial defence or space use optimization as cause for the observed sex differences, since we did not find any sex or seasonal differences in the spatial patterns of utilized dens. We suggest that aardwolves may have been ecologically constrained to exhibit social monogamy but that polymagous mating is maintained through extra pair copulations. We recommend that the evolutionary stability of these two conflicting strategies of male fitness maximization must be further investigated.
thesis submitted to the School of Animal, Plant and Environmental Sciences, Faculty of Science, U... more thesis submitted to the School of Animal, Plant and Environmental Sciences, Faculty of Science, University of the Witwatersrand, Johannesburg in fulfillment of the requirements for the degree of Masters in Science. Johannesburg 2016.
Carnivores that exhibit fission-fusion social organization can adapt group sizes to prevailing so... more Carnivores that exhibit fission-fusion social organization can adapt group sizes to prevailing social and ecological conditions. This study focuses on social organization of African lions (Panthera leo) in the Okavango Delta, a seasonally flooded wetland. We used generalized estimating equations and generalized linear mixed models to estimate the effects of flooding, as well as prey availability and intraspecific competition on group sizes of lions. During years of high flood, total lion pride sizes as well as reproductive rates declined. Prides showed extensive overlap in annual home ranges, likely as a result of habitat saturation at high densities, and pride sizes were not limited by prey availability. At the subgroup level, the number of attending cubs was the most consistent predictor of subgroup size of adult females. For subgroups without cubs, higher numbers of neighbors in adjacent, competing prides resulted in larger subgroups in focal prides, likely to maintain numerical advantage in inter-pride encounters. Larger subgroups were also formed in response to greater availability of large prey, as successfully hunting large prey requires a greater degree of cooperation. In the southwestern Okavango Delta, competition for space resulting from changing flooding regimes is a greater limiting factor for total pride sizes than food availability.
Mating systems in animal societies contain both social and genetic components. Deviations between... more Mating systems in animal societies contain both social and genetic components. Deviations between these components may have important ramifications for our understanding of the evolution of animal reproductive strategies and their ecological correlates. However, although there is ample evidence for discrepancies between genetically assigned paternities and social associations in birds, relatively few studies have documented such differences in mammals. Moreover, few studies have addressed how deviations between social mating associations and actual mating activities influence patterns of resource utilisation in males and females. The aardwolf is a socially monogamous hyaenid that exhibits polygamous mating behaviour. Suitable den sites for resting and rearing offspring is an important resource for terrestrial mammals, and dens are vital to aardwolves as thermal refugia for protection of offspring. We show that temporal patterns in aardwolf den use relates to predictions from polygamous mating rather than social monogamy. Male aardwolves used more dens, changed dens more frequently and stayed in dens for shorter periods of time than females during both wet and dry seasons. We suggest that lower male den fidelity is either caused by males trying to maximize female encounters and to monitor female activity, or that it had evolved as a non-adaptive behaviour related to elevated androgen levels. Our data did not point to territorial defence or space use optimization as cause for the observed sex differences, since we did not find any sex or seasonal differences in the spatial patterns of utilized dens. We suggest that aardwolves may have been ecologically constrained to exhibit social monogamy but that polymagous mating is maintained through extra pair copulations. We recommend that the evolutionary stability of these two conflicting strategies of male fitness maximization must be further investigated.
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Papers by Robynne Kotze