IntroductionThe purpose of this project is to assess whether the Central Kalahari Game Reserve (CKGR) can maintain viable numbers of blue wildebeest independent of surrounding areas. This study aims at evaluating the CKGR as a viable habitat patch of a mostly transformed Kalahari landscape for conservation and management of the declining and vulnerable Botswana blue wildebeest population.
Researcher: Moses SelebatsoRegion: Botswana
Organization: CKGR Research Group
BackgroundThe Central Kalahari is characterised by scarce and unpredictable rainfall, and wildlife species, particularly large ungulates historically undertook seasonal movements for forage and water.Unfortunately, the area has been transformed over time through erection of fences, livestock pressure and increasing human population. These changes have impacted negatively on ungulate migration, and wildebeest were the most hard-hit because of their high dependence on water.
Management interventions have been made like provision of artificial waterholes in the CKGR to minimise the impact of land use changes. Nonetheless, the wildebeest population continues to decline. How long and how far will this trend continue is still a mystery.
The loss of the wildebeest population in the region does not only affect species richness of the region, but the ecosystem diversity as a whole. Wildebeest form a significant proportion of the large carnivore population diet in the Kalahari. Carnivores of the Kalahari are one of the main tourist attractions in the region. However, there has never been a focused study to investigate the specifics of how the wildebeest population is doing in the region, to interrogate the success of the management interventions made, and the viability of the remnant isolated landscapes as independent entities. Or indeed to determine what factors have led to the population crashing so dramatically.
The CKGR sits in the middle of the former wildebeest migration range, and understanding the dynamics of the CKGR population will enhance development of a good management plan for the population and the CKGR, and the findings may use to extrapolate to the other areas, or inform areas specific research in those areas.
- To determine the movement patterns and home ranges of wildebeest in the CKGR and neighbouring wildlife management areas (WMAs)
- To determine factors that regulate the wildebeest population within and around the CKGR
- To determine dietary and habitat selection of the CKGR wildebeest population.
MethodologyTo monitor movement patterns of the wildebeest, one female wildebeest in a herd will be immobilised and a satellite collar deployed on it. At least 15 collars will be deployed across the study area in this way, with focus on the core area i.e., the CKGR. The collars will be programmed to record the positions of the wildebeest every 30 minutes for at least two years (which include two dry seasons and two wet seasons).To determine the dietary selection, collared wildebeest will be located and grazing animals within the herd or an adjacent herd (within the same habitat, assuming the area may have preferred plants) will be observed with the aid of binoculars. The plant species eaten by the wildebeest will be identified and recorded. Selection for grass species will be determined; preferred and ignored swards will be those areas selected or ignored by the wildebeest while grazing, respectively. The ignored areas will be those that the collared wildebeest passed through without any sign of grazing.
To determine how the wildebeest utilise the CKGR in time and space, the study area will be divided into habitat type, depending on the dominant habitat characteristics. The characteristics will be defined by pans, valleys, vegetation type (and grass or herb layer community), waterholes, fire scares, etc. Movement patterns of the collared wildebeest will be assessed across the categories throughout the year for the entire two-year study period. The movement patterns will be broken down into inter-patch and within-patch activities by analysing GPS locations using a technique that analyses the time spent per unit area to determine relative search effort along the pathway.
It is hoped that the outcomes of the project will be used to produce an article of management recommendations for wildebeest specifically and the CKGR in general.
The project has collared a total of 19 wildebeest, but 9 collared animals have died since the project started. Only one collared wildebeest died the last 12 months. As mentioned in earlier reports water seemed to have had a significant impact on mortalities. The project has, therefore, introduced a water availability and quality aspect to quantify this impact. The study will monitor artificial waterholes and collect water for quality analysis on a quarterly basis.
Annual Report 2014
2013 was a busy and productive year for the study, beginning with 8 collared wildebeest of which 7 collars worked well for more than 12 months. The survival rate of the wildebeest population seemed to have improved, although three waterholes (Piper, Molose and Letiahau) dried up in the middle of the wet season for at least a month. No confirmed mortality was associated with the drying of the waterholes, but there were fewer wildebeest recorded at Piper after this occurence than before; some may have died or moved somewhere else. In general, there was on 2/8 mortality of collared wildebeest, compared to 6/11 of the same period in 2012.
The herd that was collared at Khutse Game Reserve (KGR) continues to show consistent movement, spending the wet season in Deception Valley, northern Central Kalahari Game Reserve and the dry season in the southern section and KGR, with some excursions to the west of KGR. This seems to imply that the northern Central Kalahari Game Reserve is good for the wet season and the southern part is a good habitat for the dry season. The project is working on determining the validity of this and the factors that influence it.
Grass samples were also collected, with some samples analysed for nutritional value, and general chemical composition used in interpreting diet and habitat selection by wildebeest. Dung samples from wildebeest, springbok and gemsbok were collected to determine the diet and level of overlap, to quantify interspecific competition for grazing resources. Water samples are being collected from artificial waterholes and water availability in the waterholes monitored to relate these to habitat selection and the influence of water quality on population.
For much of 2014, laboratory analysis of grasses, water and dung are taking place with data analysis to be conducted during the last third of the year.
The CKGR wildebeest population has declined catastrophically since the early-1980s and it was a challenge to find herds for collaring. Eventually, the study deployed 16 satellite collars across the CKGR in the last 16 months, five in December 2012. However, the high mortality of wildebeest resulted in six collared animals dying in the last ten months of the project. Four of these deaths happened in the dry season and were associated with the drying up of waterholes. If these numbers were extrapolated out across other herds, this could potentially amount to some 200 wildebeest!
The collars are programmed to collect hourly fixes every day, and an average of over 3 000 fixes have been collected by each collar. All except two of the collared wildebeest spent most of the dry season around artificial waterholes, proving their importance. In the summer, they remain mainly in the northern CKGR with distribution not necessarily close to artificial water points. One group moved from KGR to northern CKGR at the beginning of the wet season, while the other moved from the north to the mid-CKGR.
The project has shown that waterholes play a critical role for survival of this water-dependent species during the dry season. This observation could explain the decline of the population in the CKGR, and other dry-land areas where natural access to permanent water has been lost. Due to the high mortality, the project aims to deploy more collars to ensure that there are at least 10 active collars at any point in time to make a viable sample size.
The study has successfully deployed a total of 11 satellite collars across the CKGR (including Khutse Game Reserve) in the last 12 months. All except two of the collared wildebeest spent most of the dry season around artificial waterholes. This showed the importance of the waterholes in the dry season.
The project experienced high mortality of wildebeest, most of which may be a result of waterholes drying. Of the 11 collared wildebeests in the study, 6 died within the last nine months of the project (55% mortality rate!). The death of 4 out of 6 animals happened directly and or indirectly because the waterhole they depended on dried up.