Abstract

In this thesis we investigate how the social organization of fish schools is influenced by the morphology and the sensory capabilities of the individuals as well as by those of their predators. We do this by means of individual-based models. Here, behavior at the group-level (schooling) is a consequence of local interactions, i.e. the responses of individuals to their neighbors and the interactions between predator and prey.We demonstrate how modeling the embodiment and the perceptual capabilities (situatedness) both of the individuals and of the predator influences their interaction and therefore the patterns at the group-level. Representing the individuals’ body affects the inter-individual spacing, such that large individuals occupy more space compared to small ones. Modeling the individuals’ situatedness, by reflecting the masking of distant neighbors by closer ones, restricts interaction to the local
environment of the individual. This influences many schooling characteristics, such as nearest neighbor distance or group speed, and in mixed schools of large and small individuals it leads to the segregation of the two sizes. In large groups school shape becomes complex and variable and the distribution of individuals heterogeneous, with regions of high and low density occurring anywhere in the school. Modeling morphological and sensory constraints of a predator affects its success in capturing prey and, therefore, influences whether schooling behavior is beneficial for the individuals or not. We demonstrate that when the predator is confusable, i.e. when its sensory capabilities to detect the movements of individuals in a group are limited, schooling is almost always beneficial.
In summary, incorporating aspects of embodiment and situatedness leads to more realistic models, first, because the real world is reflected more accurately, and, second, because they lead to a more realistic social organization of the simulated schools.