Living on the edge: physiological and behavioural plasticity of African antelopes along a climatic gradient

摘要: Climate change, habitat loss and fragmentation individually or synergistically force species to live in a sub-optimal condition terms of climate resource posing threat fitness survival the species. Hence, very pressing issue for biodiversity conservation at present is understand if are able keep pace with these rapidly changing environment conditions. To persist changes, phenotypic plasticity behaviour physiology may be most likely response long-lived endothermic because their longer generation times. Therefore, central aim this thesis investigate intra- intervariability behavioural physiological adaptation range African antelopes along spatio-temporal scales natural habitats. With climatic stress, Chapter 2, I investigated effect heat stress on diurnal activity pattern three different body size feeding types namely, eland Taurotragus oryx (≈ 420 kg; mixed feeders), blue wildebeest Connochaetes taurinus (≈180 grazer) impala Aepycerus melampus 50 feeder) across season extreme as indicated by 10 hottest days. During summer when was its highest, negatively influenced all However, they shifted timing more early morning (eland) late evening, both (wildebeest impala) avoid maximize intake food forage abundant. spring days over entire study period, only larger (eland wildebeest) whereas smaller unaffected. large apparently suffer from during due limited capacity dissipate heat. In chapter 3, possible largest antelope against thermal daily seasonal selection microhabitats based altitude microclimate southern limits distributional range. Eland actively selected lower altitudes warm microclimates winter five coldest ambient conditions were below neutral zone. contrast, did not select higher cooler it summer. evident extremely close upper end use diverse topography refuge buffer adverse cold hot condition. fourth chapter, variation resources which predicted exacerbate change fragmentation, home sizes eland, (both feeders) (a time (seasons) between two climatically contrasting areas South Africa, taking Mapungubwe National Park core area Asante Sana Game Reserve edge area. This comparative showed resource-poor dry compared resource-rich wet but also four seven times than those 3-14 Surprisingly, neither differs any within nor Mapungubwe, while average year-round that These results suggest quality availability specific local habitat. an attempt spatiotemporal context, 5, intraspecific temperature, measured amplitude, areas: one less mild (Mapungubwe Park) other long (Asante Reserve). The 24-hour amplitude temperature feeder differ sites, regardless season. grazer (wildebeest) site exhibited variability (Tb)(~4oC) minimum ~2 oC compare normothermic level site. Further, Tb (positive effect) rainfall (negative effect), proxy among reduced nutritional rather climate. (home range) (body temperature) stressful smallest impala, feeder, maintained homeothermy even though exposed habitats selecting productive habitat, i.e., riparian Mapungubwe. Sana, homeothermic status extending principle Acacia Karoo available. homeostasis ranging track heterogeneously distributed resources, ability cope food. had probably poor Interestingly, maintain particularly Not much (~4oC) Minimum lowered 2 level, extended folds Sana. failure extension therefore living physiologically environment. increase frequency intensity drought periods Africa wildebeest, grazers, will experience greater future. conclude, shows importance studying traits temporal spatial adaptive capacity, sensitivity animal Apparently, mammals cannot well influence ones ones. can overcome stresses shifting parts day optimal minimize absorption high temperatures low temperatures. (larger size) (reduced emphasizes grazers become nutritionally stressed feeders rainfall. events many world changes vegetation structure savannas browsers benefit future ruminant grazers.