Escape rooms: behavioural response of two invasive crayfish species under water decline scenarios

Climate change and invasive alien species pose a significant threat to biodiversity and the survival of native species. This study considered the impact of drought conditions on the escape behaviour through terrestrial dispersal ability of two invasive freshwater crayfish species, the red swamp crayfish (Procambarus clarkii) and signal crayfish (Pacifastacus leniusculus). Using an experimental design simulating drought conditions and Mediterranean summer temperatures, we tested the hypothesis that P. clarkii exhibits a greater tendency to terrestrial migration and a higher land-walking speed than the P. leniusculus. The results indicated that both species demonstrated strong escape behaviour, with P. clarkii showing escape success higher than P. leniusculus, and increasing with decreasing mean night temperature and crayfish weight. Although drought conditions did not trigger escape, invasive species showed increased resistance and the ability to move to more favourable environments, suggesting that drought is not an effective geographic barrier against the spread of these species. These results underline the importance of considering invasive species' ability to escape and climb as part of management and control strategies.