MSc (Zoology) / Department of Zoology / The adverse ecological effects of landscape modification by humans are well known and continue to be studied. Habitat disturbances arising from such modifications result in various levels of biodiversity loss. Amongst mammals, large carnivores are usually the first to disappear, leaving a gap in the trophic pyramid. However, ecologically adaptive small carnivores, free from the effects of intraguild predation can readily fill this gap (i.e. mesopredator release). In highly productive disturbed habitats, small mammals may thrive, reaching densities that can support an abundant and diverse suite of small carnivores. After frequent sightings of serval (Leptailurus serval) on the highly disturbed Sasol Synfuels Operations property, three camera trap surveys were conducted between 2014 and 2015 to study its ecology. The resulting data was subsequently used to study the site’s small carnivores. Multispecies occupancy modelling was used to determine detection (p) and occupancy (ψ) probabilities and estimate species richness across the study area. Site-specific covariates were then modelled against abundance values to identify any correlations. Out of 23 small carnivore species predicted to occur on the site, 11 were detected. Spatially, estimated species richness was highest in disturbed habitats, while it was slightly lower in Grassland possibly due to undersampling. Detection and occupancy probabilities were low (except for serval), with interspecies variations. It is suspected that this is the result of survey bias towards serval. The only covariate showing any significant effect was livestock presence, negatively affecting serval occupancy. Estimated species richness was used as a proxy to identify high- or low-predation areas. Within these areas, three vegetation treatments were selected (low, medium and high cover). Small mammal foraging behaviour under varying predation pressures within these treatments was then studied using the giving-up density (GUD) framework. Differences in GUDs were examined using generalised linear mixed models (GLMM). Small mammal trapping in the study area showed that four-striped grass mouse (Rhabdomys sp.; diurnal) and multimammate mouse (Mastomys sp.; nocturnal) were dominant. Nocturnal GUDs were lower than diurnal, which is interesting as four-striped grass mice are more abundant than multimammate mice. This indicates that density alone does not influence GUDs. Additionally, no significant difference in GUDs was observed between predation and vegetation treatments. I suggest that observed GUDs are linked to individual or combined impacts of interspecific differences in foraging behaviour, metabolic requirements or temporal variations in perceived predation pressure. GUDs also varied between surveys, being lower in mid- compared to early winter. This might be attributable to decreased availability of food and greater metabolic requirements in mid-winter. The results show that modified landscapes (such as the study site) can contribute to biodiversity conservation, especially of small carnivores, the adaptability of which allows them to flourish in disturbed habitats. Under favourable conditions, ecologically flexible small mammal species seem to be unaffected by the risks associated with an abundance of small carnivores. While the processes governing the dynamics of predator and prey communities in disturbed systems are not entirely clear, the conservation potential of such areas cannot be ignored and deserves more attention from researchers. / NRF

The perception of increased predation risk by nocturnal mice and other small mammals has been shown to reduce activity levels, particularly in foraging effort. Various cues of predation risk have been used in previous studies, but few have assessed the potential interactions between different types of cues. I conducted field, laboratory, and enclosure experiments using predator scents, artificial light, and microhabitat variables to determine the effects of direct and indirect cues of predation risk on foraging behavior in wild nocturnal mice. Experimental foraging trays served as artificial resource patches, and giving-up densities were measured in order to test for foraging persistence in patches exposed to cues of predation risk. Cotton mice (Peromyscus gossypinus) were used in laboratory and enclosure trials, and were the most common mice present at the sites used for field trials. Although previous foraging studies have used other Peromyscus species, this species has not been tested, but ranges over densely populated areas of the United States where artificial light could potentially affect its behavior. In outdoor and laboratory enclosures, cotton mice showed no aversive response to bobcat urine, cloths rubbed on cats, or snake sheds, but did exhibit avoidance of cat fur and artificial light. In the field experiment, mice showed a strong preference for covered microhabitats, but did not avoid bobcat urine or artificial light. Foraging in artificial resource patches also increased throughout the duration of the field experiment, possibly coinciding with a reduction in naturally-available forage. Mice in this population appear to use cover as their primary means of avoiding detection or capture by predators, though they do avoid artificial light and at least one fur-derived odor when their available options for escape are reduced.

Non-consumptive effects that predators have on prey are important to ecosystems. The perceived risk of predation can alter feeding behavior. Giving-up density (GUD) experiments have been a foundational method to evaluate perceived predation risk, but rely on the assumption that food preferences are absolute. However, nutritional preferences are context dependent and can change with risk. In my first chapter, I used spiders and grasshoppers to test the hypothesis that covariance in nutritional preferences and risk may confound the interpretation of GUD experiments. My results demonstrate that predation risk and nutritional preferences covary and can confound interpretation of GUD experiments. In my second chapter, I use a behavioral observation experiment to further explore non-consumptive effects, as well as the movement of prey in response to predation risk.

No description available.

A majority of the arid grasslands in the western U.S. have been dramatically altered by anthropogenic influences resulting in degradation and desertification. Within the arid grasslands of North America a guild of burrowing herbivorous rodents that includes kangaroo rats (Dipodomys spp.) and prairie dogs (Cynomys spp.) is often considered integral to arid grassland maintenance. As part of the larger guild of burrowing herbivorous rodents, kangaroo rats are considered to be an important keystone guild whose role as ecosystem engineers and habitat modifiers complements that of prairie dogs. Together these species organize and structure arid grassland ecosystems and the biodiversity therein, by providing a mosaic of microhabitat patches, thus increasing overall heterogeneity. In an area where black-tailed prairie dogs (C. ludovicianus) were reintroduced, I used Giving-up Density (GUD) to assess the indirect effects black-tailed prairie dogs might have on the foraging patterns of resident kangaroo rats (D. spectabilis and D. merriamii). My objective was to compare and contrast kangaroo rat foraging GUD within and along the boundary of a on a recently established black-tailed prairie dog colony with that in the surrounding unmodified native habitat. This enabled assessment of whether black-tailed prairie dogs had an influence on the perceived quality of the habitat by kangaroo rats. Kangaroo rats visited off-colony feeding trays more frequently, and collected a greater mean mass of seed per tray as well. This indicates that the kangaroo rats perceived the area off the prairie dog colony as having a lower foraging cost than on the colony or along the colony edge. I conclude that from the perspective of the seed-eating kangaroo rat, the colony is not viewed as high quality habitat. What impact the reintroduction and management of one keystone species might have on another keystone species deserves additional consideration as we attempt to restore arid grassland ecosystems.

Thesis (M.S.)--Miami University, Dept. of Zoology, 2005. / Title from first page of PDF document. Includes bibliographical references (p. 31-35).

No description available.