Elephant space use and habitat selection change across drought timescales.

Droughts are globally increasing in duration, frequency and intensity, thereby endangering the survival of wildlife species. Understanding how animals behave during drought is essential to develop conservation measures that aid wildlife survival and prevent human-wildlife conflict in a changing climate. Yet, little is known about animal behaviour during drought. Specifically, existing work on animal behaviour and drought typically does not account for the timescale and the intensity of the drought. We use 19 years of GPS data from the African elephant (Loxodonta africana), a species at risk from drought, collected in Southern Africa, where droughts are increasingly common. We study if there is a connection (i) between drought and the amount of space elephants use and (ii) between drought and elephant habitat selection. We examine drought conditions using the Standardized Precipitation-Evapotranspiration Index (SPEI) at a 1-month, a 3-month, and a 12-month timescale. We found that elephants had smaller home ranges and movement distances when their environment became drier at a 1-month timescale. Importantly, SPEI at a 1-month timescale was a better predictor of elephant home range size than precipitation and NDVI, suggesting that drought conditions may affect elephant movement through more ways than a lack of precipitation or vegetation greenness. In addition, we found that elephant habitat selection changed as a function of drought conditions at all three timescales, but the direction of the change often depended on the timescale of the drought. We found that elephants were closer to inland water and in areas with lower human population density during drought at a 1-month timescale, but farther from inland water and in areas with higher human population density when drought lasted longer. Overall, our results show that drought conditions, as measured by SPEI, predict elephant movement behaviour. We stress the importance of (i) using a drought index rather than only precipitation levels to examine drought conditions and (ii) considering the timescale at which drought occurs. These insights could help to better understand how animals behave during drought and to assess the risk of human-wildlife conflict across species, regions and drought timescales.