Terrestrial dispersal of invasive signal crayfish during vulnerable life stages.

1. Aquatic invertebrates commonly disperse between waterbodies by flight, though some decapods can emigrate from the water and walk overland. 2. The signal crayfish (Pacifastacus leniusculus, Dana) is a highly invasive species that can survive for days to weeks out of water, though it is unclear to what extent vulnerable life stages, such as ovigerous females or juvenile crayfish, terrestrially emigrate. Understanding this behaviour is important to consider during the management of crayfish stocks, since a single ovigerous female could potentially introduce hundreds of hatchlings to a new waterbody, which could themselves disperse overland. 3. Here, in a laboratory study, we examined the terrestrial emigration tendency of juvenile crayfish and compared the terrestrial emigration behaviour and overland walking speed of ovigerous and non-ovigerous females. 4. Size had a significant influence on juvenile crayfish terrestrial emigration tendency, where only those larger than 16.6 mm (carapace length) left the water. Ovigerous and non-ovigerous female signal crayfish showed no significant difference in terrestrial emigration tendency nor overland walking speed. 5. This is the first study to directly examine the terrestrial emigration behaviour of crayfish during these different life stages. These findings highlight the importance of considering animal behaviour during management strategies.