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Can wildebeest survive in the Central Kalahari?

Can wildebeest survive in the Central Kalahari?

The Piper Pans dry in July 2012, accounted for the deaths of at least 150 wildebeest
The Piper Pans dry in July 2012, accounted for the deaths of at least 150 wildebeest
Moses Selebatso

 

BY : MOSES SELEBATSO

Kalahari Research and Conservation Botswana

selebatsom@yahoo.co.uk

If restoration of the blue wildebeest population in the Central Kalahari Game Reserve is a future possibility, it is important to understand the ecological challenges facing the current remnants of the population. We have been studying the wildebeest since 2012 to improve our understanding of the factors that are determining the viability of the population in its ‘isolated’ state. 

Our study aims to understand the adaptive responses of the population to the highly seasonal variability in resource (water and food) quality and quantity, competition with springbok and gemsbok, heat stress and predation pressure. Achieving these aims requires analysis of daily activity patterns, seasonal movement, habitat selection patterns and seasonal diet composition.

The project experienced dramatically high mortality of wildebeest in the first year of study. Of the thirteen wildebeest collared, seven died, with six of those dying within the first nine months of the project (55% mortality rate). The death of four out of the seven collared wildebeest happened directly and/or indirectly because the waterhole they depended on dried up.

Three of the dead wildebeest were killed by lion and evidence indicated one was killed by wild dog as the herd was looking for an alternative water source. Dehydration (and possibly exhaustion) is suspected to have killed two, which had  travelled more than 400km in search of water and finally left the reserve, where they died.

At one of the sites eight carcasses were discovered in a radius of 200m and only six live wildebeest were found. Considering the known herd sizes of the study animals, at least 250 wildebeest died as a result of this tragedy. The overall impact of the dried waterhole to other species cannot be accounted for.

Preliminary results show that wildebeest survive the hot days of the Kalahari by maximising their activities in the cool hours of the day in the morning and late afternoon, while reducing predation risk by minimising activity at night. The wildebeest adjust to poor forage quality and high temperatures in the dry season by reducing activity levels relative to the wet season.

Wildebeest without access to water show some migratory behaviour between northern CKGR and southern CKGR / Khutse Game Reserve. Wildebeest prefer pans and valleys, especially in the wet season. This habitat forms less than 5% of the total area of the reserve, and all other ungulates including gemsbok and springbok prefer the same resource.

Unfortunately the wildebeest is not as adapted to these conditions as other ungulates are, for example utilising resources away from pans like browse and underground tubers in the dry season. These species present intense competition in the wet season and leave the wildebeest with scarce quality resources in the dry season, which may compromise the survival of the population. Most pans remained literally bare during the dry season.

Our on-going study aims to gain better understanding of the CKGR system, to identify factors influencing the decline of the population and to provide recommendations that will help in the management of the Kalahari wildebeest population.