okavango herbivore reserch
Project overview
The Okavango Herbivore Research Project started in 2005. This multi-disciplinary project aimed to increase our understanding of which factors are critical in determining the structure of the Okavango Delta's large herbivore populations.
The project had three specific aims
1. Determine the present state of the Delta's herbivore population through population dynamics
2. Investigate the relationship between resource characteristics and herbivore distribution
3. Investigate how resources and other environmental factors influence animal movement at different scales
Research was focused in the Moremi Game Reserve and adjacent Wildlife Management Areas. This region provides a good cross-section of the habitats in the Delta utilized by herbivores, being composed of seasonal floodplains, open grasslands and dry acacia, mopane and riparian woodland.
The project had three specific aims
1. Determine the present state of the Delta's herbivore population through population dynamics
2. Investigate the relationship between resource characteristics and herbivore distribution
3. Investigate how resources and other environmental factors influence animal movement at different scales
Research was focused in the Moremi Game Reserve and adjacent Wildlife Management Areas. This region provides a good cross-section of the habitats in the Delta utilized by herbivores, being composed of seasonal floodplains, open grasslands and dry acacia, mopane and riparian woodland.
methods
The project used a wide variety of field techniques to collect a broad range of data. The population demographics of all key herbivore species were recorded seasonally during driven transects. The age and sex of all individuals sighted was determined by identifying species-specific morphological differences (e.g. horn growth, size, muscular development) between age and gender categories.
Herbivore distribution and its relationship to habitat characteristics was investigated through monthly, driven herbivore transects and vegetation sampling. To enable resource characteristics and quality to be related to population density and movement, habitat surveys were undertaken at all census sites. These surveys determined the predominant grass and herbaceous species, their structural characteristics, mineral content and palatability.
Home range and movement strategies were studied by deploying GPS collars onto specific animals. This part of the study focused on Burchell's zebra (Equus quagga), which were selected because they are populous, dry-land grazers with the capacity to move large distances. GPS collars automatically record an animal's position at a pre-determined time schedule, providing detailed information on movement and habitat selection without disturbing the animal after collaring. All collars were removed once sufficient information had been gathered from each zebra.
Herbivore distribution and its relationship to habitat characteristics was investigated through monthly, driven herbivore transects and vegetation sampling. To enable resource characteristics and quality to be related to population density and movement, habitat surveys were undertaken at all census sites. These surveys determined the predominant grass and herbaceous species, their structural characteristics, mineral content and palatability.
Home range and movement strategies were studied by deploying GPS collars onto specific animals. This part of the study focused on Burchell's zebra (Equus quagga), which were selected because they are populous, dry-land grazers with the capacity to move large distances. GPS collars automatically record an animal's position at a pre-determined time schedule, providing detailed information on movement and habitat selection without disturbing the animal after collaring. All collars were removed once sufficient information had been gathered from each zebra.
findings and publications
This project was completed in 2009 and formed the bulk of Hattie's PhD project.
The major findings from this study were:
Publications:
Spatial heterogeneity in a dynamic wetland: determinants of herbivore distribution in the Okavango Delta and their relevance to conservation (PhD thesis, University of Bristol). pdf
Bartlam-Brooks, H.L.A., Bonyongo, M.C. & Harris, S. (2013) How landscape scale changes affect ecological processes in conservation areas: external factors influence land use by zebra (Equus burchelli) in the Okavango Delta. Ecology and Evolution, 3 (9), 2795-805. DOI: 10.1002/ece3.676 pdf
The major findings from this study were:
- Habitat availability and within-habitat grass characteristics in the Delta were spatially and temporally variable
- The population demographics of herbivore species were largely similar to those found in other protected areas in southern Africa. A female sex bias was found in all species, and juvenile recruitment rates were reasonable. These factors were relatively stable between regions and years over the course of the study
- The availability of floodplains and grasslands was the most important determinant of space-use at larger scales; herbivore density increased, home range size decreased and relative land-use increased with their increasing availability
- Zebra followed a selective, energy-maximising strategy throughout the dry season, perhaps due to a short resource-limiting season and lack of other temporal constraints. Selection varied with season but not region; they selected patches that improved intake rate during the more resource-limiting flood season, and patches that improved diet quality during the more productive hot dry season
Publications:
Spatial heterogeneity in a dynamic wetland: determinants of herbivore distribution in the Okavango Delta and their relevance to conservation (PhD thesis, University of Bristol). pdf
Bartlam-Brooks, H.L.A., Bonyongo, M.C. & Harris, S. (2013) How landscape scale changes affect ecological processes in conservation areas: external factors influence land use by zebra (Equus burchelli) in the Okavango Delta. Ecology and Evolution, 3 (9), 2795-805. DOI: 10.1002/ece3.676 pdf