Species-specific differences in dynamics of agonistic interactions may contribute to the competitive advantage of the invasive signal crayfish (Pacifastacus leniusculus) over the native narrow-clawed crayfish (Astacus leptodactylus)

Species-specific differences in dynamics of agonistic interactions may influence the outcome of interspecific competition and potentially contribute to competitive advantage of one species over another. In this study, we compared the dynamics of agonistic interactions of one of the most successful crayfish invaders of European freshwater ecosystems, the signal crayfish (Pacifastacus leniusculus) and the widespread native European species currently undergoing range expansion in Croatia and Europe, the narrow-clawed crayfish (Astacus leptodactylus). Comparisons between P. leniusculus pairs and the A. leptodactylus pairs demonstrated significant differences in frequency and duration of agonistic encounters: P. leniusculus dyads engaged in fewer fights, but their duration was significantly longer. In staged interactions between size-matched interspecific pairs, agonistic behaviour of P. leniusculus individuals translated into dominance over their A. leptodactylus counterparts. This indicates that the success of P. leniusculus in agonistic encounters with the native competitor might stem from its readiness to continue fighting for a longer time period, and could lead to ecological advantages during niche competition even when facing a successful native crayfish species.