Triggers affecting crayfish burrowing behaviour

Surface water inhabiting crayfish are well-known for the impact on their surroundings. This impact has been related to loss of biodiversity and deteriorating water quality for invasive crayfish. Crayfish dig burrows for various reasons like lack of natural shelters, avoiding an upcoming drought, or high crayfish density and this may lead to increased sediment transport and accelerated bank instability. All crayfish are considered to have burrowing capability, but not all species have been observed burrowing. Studies comparing this behaviour among different species in standardized ways are scarce. Crayfish burrowing was investigated under standardized laboratory conditions to reveal differences among species and their sex. All studied species occur in the Netherlands and were the native Astacus astacus (Linnaeus, 1758), the Eurasian Pontastacus leptodactylus (Eschscholtz, 1823) and the invasive North American Faxonius virilis (Hagen, 1870), F. limosus (Rafinesque 1817), Pacifastacus leniusculus (Dana, 1852), Procambarus acutus (Girard 1852), and P. clarkii (Girard, 1852). As burrowing triggers were evaluated presence of shelter, increased light intensity, increased water temperature, and increased crayfish density. Results showed species-specific and sometimes sex-specific differences in burrowing behaviour among crayfish. The response to burrowing triggers was also species-specific and no two species reacted identical to all triggers. Absence of shelter was a strong driver to burrow for A. astacus, F. limosus and F. virilis, while increased light intensity triggered burrowing behaviour in P. leptodactylus, P. acutus and P. clarkii and lowered activity of F. limosus. Burrowing behaviour of P. clarkii was mostly influenced by increased water temperature. Significant differences between females and males were observed for P. leptodactylus, P. leniusculus and P. acutus in the shelter, increased density and increased water temperature treatment, respectively. Understanding the triggers that invoke burrowing may help managing populations of these invasive species.