| الوصف: |
The tendency for African ungulates to form multi-species aggregations is well known and six hypotheses to explain these associations have been made: Inter-specific competition; Intra-specific competition; Autecological factors; Predators; Food facilitation and Random factors. Certain testable predictions follows from these hypotheses. The nature of the relationships in five African ungulates, was investigated over two years in the Katavi National Park, Tanzania. Data relevant to behaviour, group compositions and environmental factors were collected for all species encountered. Only data concerning zebra, topi, waterbuck, buffalo and elephant were considered for the subsequent analysis. The following calculations and tests were carried out in order to test the various hypotheses: 1) Habitat overlap, 2) Vigilance and herd size in the presence or absence of predators, 3) Coincidence of habitat visits, 4) Vigilance and herd size in the presence or absence of another species, 5) Effect of grazing by one species on that of another on the same day and over the following ten days and 6) Comparison between distances to nearest non-conspecific and nearest conspecific. The results showed a clear change in the nature of the relationships according to season. In extreme cases, such as the topi - zebra interaction, it changes from being a positive arrangement against predation, to competition for food. Predator detection or avoidance was not found between any of the three smaller species and either of the two larger species. Zebra, topi and buffalo were all found to be in competition for food. Food facilitation was an important factor in describing the relationship between zebra and other species. Due to only a few observations being possible on elephant, the interpretation of most of the associations involving elephant are provisional. In most of these associations, autecological factors were considered to be involved. |
