Abstract:
Southern Africa is expected to experience increased frequency and intensity of droughts through
climate change, which will adversely affect mammalian herbivores. Using bio-loggers, we tested
the expectation that wildebeest (Connochaetes taurinus), a grazer with high water-dependence,
would be more sensitive to drought conditions than the arid-adapted gemsbok (Oryx gazella
gazella). The study, conducted in the Kalahari, encompassed two hot-dry seasons with similar
ambient temperatures but differing rainfall patterns during the preceding wet season. In the drier
year both ungulates selected similar cooler microclimates, but wildebeest travelled larger distances
than gemsbok, presumably in search of water. Body temperatures in both species reached lower
daily minimums and higher daily maximums in the drier season but daily fluctuations were wider
in wildebeest than in gemsbok. Lower daily minimum body temperatures displayed by wildebeest
suggest that wildebeest were under greater nutritional stress than gemsbok. Moving large distances
when water is scarce may have compromised the energy balance of the water dependent wildebeest,
a trade-off likely to be exacerbated with future climate change.
