How free-ranging ungulates with differing water dependencies cope with seasonal variation in temperature and aridity.

Melinda Boyers,Francesca Parrini,Barend F N Erasmus,Norman Owen-Smith,Robyn S Hetem

doi:10.1093/conphys/coz064

Melinda Boyers, Francesca Parrini + Show 3 more

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https://doi.org/10.1093/conphys/coz064

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Journal: Conservation physiology	Publication Date: Jan 1, 2019
Citations: 20	License type: CC BY 4.0

Affiliation: University of the Witwatersrand

Abstract

Large mammals respond to seasonal changes in temperature and precipitation by behavioural and physiological flexibility. These responses are likely to differ between species with differing water dependencies. We used biologgers to contrast the seasonal differences in activity patterns, microclimate selection, distance to potential water source and body temperature of the water-independent gemsbok (Oryx gazella gazella) and water-dependent blue wildebeest (Connochaetes taurinus), free-living in the arid Kalahari region of Botswana. Gemsbok were more active nocturnally during the hot seasons than in the cold-dry season, while wildebeest showed no seasonal difference in their nocturnal activity level. Both species similarly selected shaded microclimates during the heat of the day, particularly during the hot seasons. Wildebeest were further than 10 km from surface water 30% or more of the time, while gemsbok were frequently recorded >20 km from potential water sources. In general, both species showed similar body temperature variation with high maximum 24-h body temperature when conditions were hot and low minimum 24-h body temperatures when conditions were dry, resulting in the largest amplitude of 24-h body temperature rhythm during the hot-dry period. Wildebeest thus coped almost as well as gemsbok with the fairly typical seasonal conditions that occurred during our study period. They do need to access surface water and may travel long distances to do so when local water sources become depleted during drought conditions. Thus, perennial water sources should be provided judiciously and only where essential.

Highlights

Climate change is already affecting numerous organisms (Parmesan and Yohe, 2003; Pio et al, 2014)
When rains are delayed at the start of the wet season, species are concurrently exposed to high ambient temperatures, poor forage quality and limited access to water during a time when their body reserves are low (Fynn, 2012; Owen-Smith, 2008)
Behavioural flexibility is likely to be an animal’s primary response to changes in climatic conditions (Hetem et al, 2014), with responses likely to be different between water-dependent and water-independent species

Summary

Introduction

Climate change is already affecting numerous organisms (Parmesan and Yohe, 2003; Pio et al, 2014). Animals may alleviate radiant heat loads during the day by seeking shade, at the cost of diurnal foraging activity (Fuller et al, 2016). They may compensate to some extent by foraging more at night (Hetem et al, 2012b), thereby elevating their exposure to predation by nocturnal carnivores (Owen-Smith, 2015). Understanding the physiological and behavioural flexibility of individuals currently inhabiting hot and dry environments is crucial to improving predictions about how species might respond to hotter and drier environments predicted for arid and semi-arid regions in Africa under climate change (Engelbrecht et al, 2015)

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