Behavioral individuality in Drosophila – The diverse routes to uniqueness

Over the past decade, several behavioral studies have demonstrated that idiosyncratic behavioral traits remain stable over long time periods. The stability of individually variable characteristics over time is often referred to as an animal's individuality or personality. Our work demonstrates that this individuality depends not only on nature or nurture, therefore genes and the environment, but also stochastic processes or chance play an important role. However, most animal studies have focused on individual variability in a single behavioral context, whereas it is well-established that animal behavior is highly context-dependent. It therefore remains an open question whether individual behavioral traits persist in different behavioral contexts. For instance, one individual might be more visually guided than another, or rely on one particular visual cue, or even one specific visual cue only under certain environmental conditions. We are using a combination of well-established and novel behavioral assays to investigate this question over a range of behavioral traits and contexts. We explore the persistence of behavioral traits under changing environmental contexts like illumination, temperature, and arena shape in both walking and flying Drosophila melanogaster. We can show that some individually variable behavioral features persist across different environmental contexts. However, the persistence of most behavioral traits varies considerably depending on which specific environmental parameters are modified. While some behavioral traits like the overall motivation to walk correlate across all tested contexts, parameters like walking speed, angular variability, or handedness persist only when the temperature or illumination changes. In contrast, these parameters are strongly altered upon changing either arena shape or modality of movement (walking vs. flying). In summary, our recent work shows the persistence or inconsistency of behavioral traits across different contexts, that we found independent of either genotype or gender.