Movement patterns of an invasive crayfish, Procambarus clarkii, in a temporary stream of southern Portugal.

Radio-telemetry was used to determine the spatial behaviour of the invasive crayfish, Procambarus clarkii (Girard), in a temporary stream in southern Portugal during the dry period. One aim was to understand the behavioural mechanisms that allows crayfish to withstand extreme environmental conditions. This study can also provide data relevant to developing programmes for the prevention of this species’ expansion. During a drought, the red swamp crayfish does not aestivate. Except for one female, radio-tagged specimens dispersed within the habitat with a speed ranging 1-11 m·d-1. A wide inter-individual variation was shown in the extent of locomotion. Locomotory speed was significantly correlated with crayfish size. Movement was not related to sex, the hour of the day, or several abiotic parameters of the habitat, with the exception of the water depth. Movement patterns appeared complex: one or more short peaks of intense locomotion often alternated with periods of slow speed or no movement. Procambarus clarkii maintained its temperature below environmental extremes, largely by occupying burrows or refuges. Although shelters were limiting in the habitat under study, following a move, radio-tracked individuals did not re- occupy the same burrow, but rather entered the first one found vacant. Refined orienting capabilities have been described in decapods including crayfish, but in this context homing behaviour seems not to occur.