Elephants in a landscape of risk: spatial, temporal, and behavioural responses to anthropogenic risk in African savannah elephants

Abstract

African savanna elephant (Loxodonta africana) populations have declined due to poaching for the ivory trade. Elephants and humans also increasingly share ranges and resources. This thesis investigates whether and how human-mediated risk influences elephant space use, activity patterns, resource use, grouping patterns, and sex differences in responses to risk, in the Ruaha-Rungwa ecosystem, Tanzania. This area experienced multiple poaching surges and has increasing levels of human activity. I applied occupancy models to elephant occurrence data to investigate space use in relation to risk and environmental factors. Elephant occurrence was negatively associated with human population densities and conversion to agriculture, as well as elephant carcass occurrence (a proxy for poaching risk) and illegal human use. Using camera trap data I compared active periods, grouping patterns, and use of roads and water sources at one low-risk site and three high-risk sites. Male and female elephants were more nocturnal in high-risk versus low-risk sites, including use of water sources; this was more pronounced for cow-calf groups than for lone males. In the high-risk versus low-risk sites, elephants were active for less time overall, avoided movement on roads, and male elephants associated more with males and cow-calf groups. I assessed how risk influences elephant use of water sources using camera trap data. Elephant use of a high-risk resource was driven by seasonal variation in water availability, and use of high-risk water sources was more nocturnal than use of low-risk water sources. Males, but not females, adjusted group size in relation to risk. I discuss costs associated with risk-induced behavioural shifts, including a reduction in total active time and effects on body condition, and show that the consequences of elephant poaching in Ruaha-Rungwa extend beyond effects on population size and structure. I suggest that risk-avoidance behaviour may enable elephants to persist in increasingly human-dominated landscapes.