On the Fractal Characterisation of Zooplankton Motion: Applications and Perspectives

The analysis of motion patterns reveals important aspects of the strategies employed by organisms to interact with the environment and among them, and in a broader sense of the behavioural adaptations developed to survive in a competing world. Of the several parameters that have been applied in literature, fractal dimension is probably one of the most used and widespread. This parameter investigates the degree of convolutedness of a trajectory and the irregularity of the motion. Despite its usefulness and the almost countless applications to different animal trajectories, the use of fractal dimension in motion behaviour is still somehow controversial. In this chapter we will briefly summarise the main characteristics of fractal analysis, and we will then focus on the aspects that are more debated, providing some critical comparisons with other commonly used parameters. The final part of this contribution will be centred upon a specific application, the behaviour of zooplanktonic organisms, small inhabitants of the aquatic world that play a key role in the function of marine and freshwater ecosystems.