Oliveira, D. F.; Soares, M. S.; Anastacio, P.; Banha, F.

Procambarus clarkii is a prominent example of a successful invasive species, and its ability to disperse is known to be a key characteristic. The ability to disperse dictates the spread and impacts an invasive species has, with various known factors influencing it, such as temperature and circadian rhythms. However, there is still limited information on how crayfish social interactions influence their dispersion, and even already known factors still require further investigation. As such, the goal of this study is to deepen the knowledge of the Procambarus clarkii dispersion capabilities. To achieve this, two laboratory experiments were conducted to address the crayfish dispersal abilities, namely their speed, under controlled conditions. The first experiment tested the effect of the interaction of two temperatures (16 and 22 degrees celsius) and the presence or absence of food in a fully lit or darkened room. The second experiment tested the effects of pairing individuals of the same and opposite sex and of different and/or similar sizes. Three velocity values were obtained: the first considered the crayfish\'s final position on the track, the second considered the crayfish furthest point on the track, and finally, the third considered the total distance travelled by the crayfish. Results show that when exposed to the higher temperature and in the absence of food, crayfish increased their speed, but size and sex did not seem to have an effect overall. When paired, female crayfish that were behind another crayfish achieved faster speeds on average than males in the same position. We also found that smaller females had faster velocities when paired with bigger females than with bigger males. The observed increase in speed with higher temperatures suggests that, in the face of current global and habitat changes, P. clarkii rate of spread may accelerate. However, if provided with a reliable food source, crayfish may disperse less. Still, more research is needed to expand our understanding of which factors contribute to P. clarkii dispersion capabilities, as this may prove important in formulating new plans and strategies to limit its impacts.