Fig. 2

Violin plots of the different sea urchin movement variables analysed: a Sea urchin trajectories were on average straighter (less tortuous) and b faster (higher mean speeds) in the predator treatment (n = 21) compared to controls (n = 29). c Scaling exponents of the qth order structure functions indicated that, on average, sea urchins shifted from a wide range of spreading patterns, including Brownian motion, in control conditions to superdiffusive and marginal ballistic motion in the presence of predator chemical cues. The dashed and dotted lines in panel c represent the theoretical slope of purely Brownian and ballistic motion respectively. Different lower-case letters indicate statistically significant differences (see also Table 1). Shaded areas (‘violin-plots’) illustrate the kernel probability density of the data for each experimental treatment. Black points correspond to each individual observation (each sea urchin)