Research


Large herbivore community structure and differential spatio-temporal habitat selection in the Okavango Delta, Botswana

A three-year PhD study by Mpaphi Casper Bonyongo. Completed 2004.


Below is a synopsis of the aims of the study which is now completed.

Introduction

This project investigates the ecology of large herbivores in the Okavango Delta. Emphases are placed on habitat classification, seasonal habitat and forage selection, species packing, co-existence and seasonal changes in community structure. The research also investigates the influence of productivity and forage quality on seasonal grazing patterns and resource partitioning patterns of herbivores. Particular attention is focused on buffalo and zebras since they are ecologically similar in terms of foraging behaviour. They are both bulk roughage grazers, which suggests that potential competition exist.

Study site

The Okavango River Delta is a large land locked alluvial fan located in the northwestern part of the semi-arid Kalahari basin of the Northern Botswana. It covers an area of about 22 000 km2 of which approximately 6 000 km2 is permanent swamps, 10 000 - 12 000 km2 is seasonal flooded grasslands and the rest is low-lying dry savannah. Water and sediments are distributed across the fan by meandering and isolated channels, which are flanked by extensive swamps. The position of the channel, hence the distribution of water and sediments are constantly changing due to channel avulsion, leading to a fairly even distribution of sediments across the upper permanently flooded portions of the fan. The Okavango Delta lies within the grabens at the southern extremity of the East African rift system. It represents the terminal depository for the Okavango River system, which drains from central Angola, as all the sediments transported by the River are deposited on the fan. The area is of international environmental importance as one of very few remaining relatively undisturbed inland Delta ecosystems in the world.

Problem definition and justification

The Okavango Delta is a complex system such that fully integrated studies are rare in the literature. Data on aspects such as productivity, plant-herbivore interaction, herbivore-herbivore interaction, variation in flooding regimes, nutrient flux, and vegetation monitoring is widely scattered, largely unpublished and difficult to assimilate. As a result the ecology and ecological functioning of the Okavango Delta ecosystem is poorly understood. An understanding of the ecology of large mammalian herbivores is fundamental to the development of sustainable management and effective economic development strategies within of the Okavango Delta and other similar ecosystems. Large herbivores are major determinants of ecosystem functioning and dynamics of terrestrial biomes. The Okavango Delta is a closed system as a result of the veterinary fences. This has negative impact on naturally migratory species like zebra and wildebeest. The Okavango Delta and its rich assemblage of wild herbivores is under continuous threat from competing land uses encroaching from tourism activities and demand for grazing resources for livestock and demand for water from the rapidly expanding village of Maun. An understanding of the ecology of large mammalian herbivores is fundamental to the development of sustainable management of the Okavango Delta resources.

Materials and methods

Data will be collected for a period of eighteen months. Habitat classification and mapping will be done using satellite imagery. Seasonal habitat selection will be investigated through direct field observation, aerial surveys and GPS tracking. Data on seasonal geographic positions of herbivores will be overlaid on habitat maps using ARCVIEW, GIS software. Forage quality will be analysed monthly through chemical and sward structure analysis.

Contact details

Email: Mpaphi Casper Bonyongo