Contrasting capabilities of two ungulate species to cope with extremes of aridity

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.

Reflections of ecological differences? Stress responses of sympatric Alpine chamois and red deer to weather, forage quality, and human disturbance

“…Depending on the physical and climatic characteristics of their typical habitats, different species within the same order have developed diverging physiological or behavioral adaptations to cope with challenges in their environment (Boyers et al, 2021 ; Haim & Izhaki, 1995 ; Klein, 2001 ). In highly seasonal habitats, such adaptations can involve, for example, the build‐up of fat reserves, changes in activity patterns and digestive physiology, reallocation of body resources or migratory behavior to meet predictable food shortages, or changes in blood circulation and coat thickness to adapt to temperature changes (Arnold, 2020 ; Blix, 2016 ; Geiser & Ruf, 1995 ; Lovegrove, 2005 ; Ruf et al, 2012 ).…”

“…Two species living in sympatry but with different ecological adaptations may therefore differ in their stress reactions to adverse environmental stimuli or changes in forage conditions. These responses may in turn have direct implications on species’ ability to cope with climate change (Angelier & Wingfield, 2013 ; Boyers et al, 2021 ).…”

Remote monitoring of short‐term body mass variation in savanna ungulates

“…Seasonal water scarcity results in extensive grasslands with scattered trees, supporting very high densities of herbivores. To deal with resource scarcity and to maximize fitness, large herbivores inhabiting seasonally variable environments often optimize energy expenditure by giving birth and mating when resources are abundant (Côté & Festa‐Bianchet, 2001; Mason et al., 2012; Ogutu et al., 2015), and migrating when resources are scarce (Barker et al., 2019; Boyers et al., 2019, 2021; Debeffe et al., 2017; Spaan et al., 2019).…”

“…environments often optimize energy expenditure by giving birth and mating when resources are abundant (Côté & Festa-Bianchet, 2001;Mason et al, 2012;Ogutu et al, 2015), and migrating when resources are scarce (Barker et al, 2019;Boyers et al, 2019Boyers et al, , 2021Debeffe et al, 2017;Spaan et al, 2019).…”

Mitigating anthropogenic barriers to facilitate distributional shifts helps reduce vulnerability of a large herbivore to climate change

“…Animals may be directly affected by climate change via fundamental alterations in local climate (e.g. becoming too hot or too dry) that are incompatible with physiological tolerances of species (Moyer‐Horner et al., 2015; Yandow et al., 2015; Veldhuis et al., 2019; Boyers et al., 2021). Indirectly, an increase in the frequency and severity of droughts and wildfires (Cook et al., 2019; Williams et al., 2020; Keeley & Syphard, 2021) can alter the distribution of suitable habitats, and the quantity and quality of food supplies, that consequently may alter species distributions (Cahill et al., 2013; Aikens et al., 2020).…”