Effects of tail loss on the movement patterns of the lizard, Psammodromus algirus

1. Many lizards use caudal autotomy as a defensive strategy. However, subse quent costs related to the alteration of locomotor abilities might decrease the fitness of individuals. In this paper, the movement patterns of sponta neously moving Psammodromus algirus lizards and their escape performance ru nning at high speed were compared before and after tail loss. A control tai led group was also studied to assess the repeatability of locomotor pattern s between trials. 2. Tail loss had a significant effect on spontaneous movement patterns. Tai lless individuals moved at significantly slower speeds during bursts of loc omotion, and distances moved within bursts were significantly reduced. The overall time spent pausing increased, and, as a result, overall speeds decr eased to an even greater extent than burst speeds. However, mean durations of individual locomotor bursts and mean pause durations did not change sign ificantly after tail loss. 3. Loss of the rail decreased mean stride length, although the positive rel ation between stride length and speed was retained. 4. Escape performance was also greatly affected; loss of the tail resulted in substantially reduced attained, maximal and overall escape speeds. These changes resulted in shorter escape distances (the time of the first pause after the initiation of the escape response) because the mean duration of e scape responses did not change. 5. The relevance of these alterations for the ecology of this species, and how individuals may compensate for the costs of tail loss, favouring autoto my as an escape strategy, are discussed.