Group Territoriality of the African Lion: Behavioral Adaptation in a Heterogeneous Landscape (Paperback)

This thesis examines the evolution of group territoriality---a compelling form of social behavior marked by notable levels of cooperation and violence. My research focuses on the evolution of social behavior in African lions and places numerical advantage in territorial competition at the foundation of the lion social group. Results also suggest how group-territorial behavior was shaped by a heterogeneous savanna landscape. This research required, above all, an understanding of how lion's view their habitat, as territoriality is an ongoing effort to gain and maintain exclusive access to a valuable share of real estate. Using a 38-year dataset on lions in the Serengeti National Park, Tanzania, I determined that a fitness-based (as opposed to density-based) measure is a superior gauge of lion habitat quality. Average female per capita reproductive success was significantly correlated with proximity to river confluences. This single landscape feature, which provides food, water and shelter, best describes the value of Serengeti lion real estate. With this information, I estimated pride territory quality and established that larger prides do indeed maintain control of the highest value habitat. In addition, neighbors had a significant negative impact on female reproductive success and survival, indicating that inter-group competition strongly affects fitness. Pride subgroups were also significantly larger when a pride had more neighbors, suggesting sensitivity to risk of encounter. Males played a more important role in group-territorial competition than expected, and female mortality was strongly associated with male neighbors, suggesting that males may exhibit adaptive lethal aggression, which tips the balance of power in favor of their own pride. Simulation modeling demonstrates that group territoriality may be an emergent property, which evolves due to the synergistic effects of landscape structure and advantages of forming territorial social groups. The model also shows that group territoriality is more likely to evolve in high density populations and that rates of inter-group conflict are significantly higher in heterogeneous landscapes. These results help us to understand how lions became social as a result of adaptation to the heterogeneous savanna landscape, and also provide insight into the evolution of other group-territorial species, including humans.