The ecological and life history correlates of boldness in free-ranging lizards

© 2018 Ward-Fear et al. In many animal populations, individuals exhibit repeatable behavioral traits across a range of contexts, and similarly, individuals differ in ecological traits such as habitat use, home range sizes, growth rates, and mating success. However, links between an individual's positions on behavioral vs. ecological axes of variation remain relatively unstudied in the wild. In the course of fieldwork on a remote floodplain in tropical Australia, we quantified boldness and ecological traits in 86 free-ranging (radio-tracked) monitor lizards (Varanus panoptes). These large (up to 7 kg) lizards exhibited a spectrum of boldness, as reflected in correlated scores of responses to approach, handling, and novel prey. Bolder lizards had larger core home ranges and higher mating success and spent more time in areas of high predator abundance, and their seasonal regimes of predation-induced mortality differed from those of shyer lizards. Thus, behavioral differences among lizards underpin much of the variation in ecological traits and individual fitness within this population. Analyses of ecology and microevolution in natural populations cannot afford to ignore the complex covariation between behavior, ecology, and evolution in the wild.