Studies on the behavioural ecology of Przewalski horses (Equus przewalskiiy) recently reintroduced into Hustai National Park, Mongolia were carried out between 1998 and 2000. Home range size and habitat use, social, marking, and vigilance behaviour, and their reaction to flies were quantified. Home ranges of harems ranged from 129 ha to 2399 ha, with core areas of between 61 ha and 1196 ha. There was no relationship between range size and harem size, or length of time since release. The more nutritious vegetation at lower elevations was preferentially selected. The horses rested near ridges during the hotter parts of the day where there were fewer flies, and grazed in the valleys in the mornings and evenings. Woodland areas were used to shelter from the sun, despite their high fly abundance. Muscid flies were most frequently caught; Tabanids were rare. Dominance was related to age, aggression and length of time in the harem. The frequency of associative behaviours did not correlate with any social factor, but had a hygienic function. Stallions marked stud piles wid mare eliminations in different ways suggesting different functions. In addition to being vigilant for predators, the horses appeared to scan for social cues and food patches. Home range size and habitat use, and general pattern of marking and vigilance behaviour, of the wild Przewalski horses were similar to those seen among feral domestic horses, although they tended to be less aggressive than captive and feral horses. So far, the re-establishment of przewalski horses into HNP appears to have been successful, although constant monitoring of the population is necessary. As the population grows, there will be potential problems to do with exceeding the carrying capacity of the park and hybridisation with domestic horses. The future management of the horses is discussed.

Group size affects individual and collective vigilance levels of prey species. As individual vigilance decreases with increasing group size, the indirect risk of predation to each individual and the group as a whole will also decrease (dilution and many-eyes effect) which may have a decreasing effect on stress responses on group level as well. Where predation risk is low, other factors like group size might influence stress-related glucocorticoid output in prey species. I test the relationship between group size and individual and collective vigilance levels in a plains zebra (Equus burchelli) population living in an environment with low adult predation risk due to the absence of lions (Panthera leo) in the Dinokeng Game Reserve (DGR). I also test for an effect of season (wet vs. dry) on these levels. Vigilance levels are expected to be higher in summer than winter, due to a seasonal influence on susceptibility to predation or the ease of predator detection. Finally, I test if the presence of foals in a band influences individual and collective vigilance levels. Mothers are expected to increase their vigilance levels since foals are most susceptible to predation by smaller predators in the reserve. I also aimed to specifically investigate how group size affects adrenocortical endocrine activity in male and female individuals of plains zebra bands living in an environment with low predation risk. With an increase in group size, and individual vigilance expecting to decrease, the indirect risk of predation to each individual and the group as a whole will also decrease (due to both dilution and many-eyes effect) which may decrease stress on group level as well. Affiliative social interactions between females could also have the effect of improving fitness and reducing stress levels in this species. We therefore evaluated the reliability of different enzyme-immunoassays (EIA) for monitoring glucocorticoid metabolite levels in plains zebra faeces by conducting an adrenocorticotropic hormone (ACTH) challenge test and associated translocation event. Individual vigilance decreased with group size, confirming a classic group size effect; while collective vigilance remained constant meaning individuals could reduce their own scanning and rely on scanning by other group members. Individual vigilance differs between seasons, with higher levels recorded in summer, but no seasonal effect is found on rate of scanning and collective vigilance. Interestingly, bands with foals have a lower level of individual vigilance than bands without foals, which may be due to added nutritional stress on mothers during lactation. A constant collective vigilance level means mothers may be able to increase foraging time without increasing predation risk. I successfully identified two group-specific EIAs as suitable for assessing adrenocortical endocrine activity in male and female plains zebra, but gender-specific differences in response to ACTH administration and translocation were detected. In winter, bands of free-ranging plains zebra differ significantly in terms of faecal glucocorticoid metabolite (FGM) output, but due to the fact that the bands tested also differed in size as well as composition, the potential band size effect were analysed for males and females separately. Males in bands of greater size exhibit higher FGM levels than males in small bands; explained by the females’ need for protection, resource competition and reproduction pressure. FGM levels in females did not differ between bands of different sizes, indicating that potential changes in vigilance behaviour per se might not alter FGM output in a low-predation risk environment. This study confirms firstly, the classic group size effect on vigilance in plains zebra in this low predation risk environment and secondly, that group size and sex should be considered when looking at FGM levels in this social species. / Dissertation (MSc)--University of Pretoria, 2012. / Zoology and Entomology / unrestricted

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