Animal personalities on the move

Movement is one of the most conspicuous features in the life of animals. Strikingly, individuals differ drastically in their movement behaviour, and these differences are associated with other differences in morphology, physiology, and behaviour. In this thesis, I investigate how movement types emerge, how they are maintained, and how they relate to other aspects of ‘animal personality’. In the empirical part of my work, I studied migration-related traits in three-spined sticklebacks. To this end, I compared ‘resident’ populations that were prevented from migration to the sea by human-made barriers with close-by ‘migrant’ populations. After only 50 years of isolation, the residents differed considerably from the migrants in whole suites of morphological and behavioural traits. A breeding experiment revealed that part of this variation reflects genetic differentiation and, hence, rapid evolution. To map the differences between fish in more detail, we established a semi-natural mesocosm of connected ponds, where many fish can be tracked over extended periods of time. Interestingly, resident- and migrant-derived fish did not differ in their short-scale movement (within ponds), but migrants had a considerably higher long-scale movement tendency (across ponds). I also conducted some theoretical studies on the causes and consequences of personality variation in a foraging context. I showed that the spatiotemporal variation of resource availability can lead to the evolution of behavioural polymorphism, which in turn has marked implications for the spatial distribution of foragers. Overall, my work illustrates that movement, which is a crucial link between an organism and its environment, can diversify rapidly, and that movement diversity is associated with other phenotypic and behavioural diversity.