Body mass is a key ecological trait and the distribution of different body-sized organisms in communities affects their structure, stability and functioning. Therefore, it is crucial to understand the drivers of the coexistence of different sized organisms. Body size has been identified as an important factor for the coexistence of the diverse assemblage of African mammalian herbivores, representing a trade-off in nutritional requirements (food quality vs food quantity). Also, body size affects the risk of being predated and has thermoregulatory consequences. Here, we investigate the ecological consequences of these different constraints for different-sized herbivores. We used camera trap data to study the effects of food requirements, predation risk and thermoregulation on the daily activity patterns of different sized savanna herbivores.
Results/Conclusions
Larger herbivores were found to be more continuously active throughout the day, suggesting increased feeding times to meet higher food requirements. Furthermore, intermediate sized herbivores (10 – 400kg) reduced overlap with predator activity most by showing highest activity during the day. In contrast, largest herbivores (> 400kg) avoided activity during these hot hours (midday), probably to prevent overheating. The smallest herbivores (< 10 kg) did not follow these general trends and were also most active during the night. Overall, our results show that body size has profound ecological consequence on the temporal activity patterns of savanna herbivores through multiple constraints (food requirements, predation risk, thermoregulation). Furthermore, a trade-off emerged between predation risk and thermoregulation, where highest predation risk is perceived at the cooler hours of the day.