Linking behavioural type with cannibalism in Eurasian perch

Abstract

The propensity to kill and consume conspecifics (cannibalism) varies greatly between and within species, but the underlying mechanisms behind this variation remain poorly understood. A rich literature has documented that consistent behavioural variation is ubiquitous across the animal kingdom. Such inter-individual behavioural differences, sometimes referred to as personality traits, may have far-reaching ecological consequences. However, the link between predator personality traits and the propensity to engage in cannibalistic interactions remains understudied. Here, we first quantified personality in Eurasian perch (Perca fluviatilis), measured as activity (time spent moving) and sociability (time spent near conspecifics). We then gave perch of contrasting behavioural types the option to consume either conspecific or heterospecific (roach, Rutilus rutilus) prey. Individual perch characterized by a social-active behavioural phenotype (n = 5) selected roach before being cannibalistic, while asocial-inactive perch (n = 17) consumed conspecific and heterospecific prey evenly. Thus, asocial-inactive perch expressed significantly higher rates of cannibalism as compared to social-active individuals. Individual variation in cannibalism, linked to behavioural type, adds important mechanistic understanding to complex population and community dynamics, and also provides insight into the diversity and maintenance of animal personality.

Fig 1. Mean swimming activity (s) in relation to mean shoaling (s) for all tested perch (N = 53).

Circles represent the fish classified (cluster analysis) as social-active behavioural type (N = 9), while triangles represent asocial-inactive fish (N = 44). Dark symbols denote the 22 individuals selected (based on CV, $\mathrm{\sigma }/\overline{\mathit{x}}$) as experimental fish for the selective cannibalism trials. Note that multiple fish had 0 activity and 0 sociability meaning the triangle located closest to the origin represents multiple individuals.

Fig 2. Selection of prey perch by focal perch with social-active (n = 5) and asocial-inactive (n = 17) activity/sociability behavioural types during selective cannibalism trials.

Whiskers represent 10^th– 90^th percentile, filled dots represent outliers, and the broken line denotes no prey selectivity (α = 0.5). The * denotes a significant difference at the 0.05 > p > 0.01 level.