Behavioural plasticity of alternative reproductive tactics

Animals exhibit an astonishing diversity in their reproductive behaviours. In some special cases, these differences are even known to exist within a single species, for instance where different types of males (known as morphs) exhibit distinct reproductive strategies. These so- called alternative reproductive tactics (ARTs) correspond to differences in ornaments, body size, and behaviour. Morphs may depend on extrinsic factors (age, body condition, etc.) or can be genetically determined and thus fixed for life. However, even within these morphs, there is a certain range of individual behavioural differences and flexibility in behavior. Indeed, behavioural flexibility should be beneficial in variable environments, for instance when males of other morphs are absent, allowing individuals to adjust their reproductive behaviours and increase their reproductive success. However, to what extent species with ARTs exhibit plastic responses in variable social environments is largely unknown. In this project study, we aim to investigate the extent to which birds with ARTs are capable of adapting their behavior to variable social contexts. We will focus on two charismatic bird species: ruffs (Calidris pugnax) and spotted bowerbirds (Ptilonorhynchus maculatus). Males in both species exhibit either a conventional tactic where males compete within a display arena to be chosen by females, or a parasitic, sneaking tactic that exploits the investment of competing males to obtain copulations opportunistically. The questions that remain to be answered are the following: can males exhibit behaviors that are typical for other morphs under specific social contexts? Do courtship displays as well as dominance hierarchies vary when other morphs are removed? Do females adjust their reproductive output according to the social context? This project will use a combination of experimental approaches in controlled laboratory conditions in ruffs, and in the wild in spotted bowerbirds. We will study ruffs at the Max- Planck-Institute for Biological Intelligence (Germany), in collaboration with Dr. Clemens Kupper, and investigate the effect of the experimental manipulation of the social environment on the expression of ARTs. In spotted bowerbirds, we will remove resident males to investigate behavioural plasticity in sneaker males in the wild, in collaboration with Prof. Leonida Fusani (Konrad Lorenz Institute of Ethology, Vienna). We will combine cutting-edge methodologies for behavioural analysis including machine learning techniques for movement tracking with established paradigms to investigate social and dominance networks and parentage analysis during the experimental manipulations. Our studies will show how behavioural repertoires in ruffs and bowerbirds are modulated by the social environment under which they are expressed. The results will improve our understanding on the origin and evolution of behavioural diversity.