SHORT-TERM, MEDIUM-TERM, AND LONG-TERM REPEATABILITY OF LOCOMOTOR PERFORMANCE IN THE TIGER SALAMANDER AMBYSTOMA-CALIFORNIENSE

Both burst and endurance performance may be crucial determinants of the lifetime fitness of an organism, especially for many amphibians where burst allows for predatory escape and endurance may contribute to migratory ability. However, there are no analyses of the long-term stability of locomotor performance for any amphibian, hindering efforts to extrapolate from single measurements to lifetime performance estimates. We present an analysis of individual repeatability of burst speed and endurance locomotor performance over short (seconds), medium (hours), and long (15 months) time intervals for a large sample of Ambystoma californiense. Burst speed is significantly repeatable over all three time intervals. We found a significant tiring effect for burst speeds when measured only seconds apart; apparently several hours are required for complete physiological recovery. Endurance repeatability reaches or approaches statistical significance when measured over periods of several days, but is not repeatable over 15 months. We postulate that both burst and endurance are ecologically important; our results confirm that single measurements of performance may not provide accurate profiles of lifetime locomotor ability. We also present a literature review of locomotor performance repeatability studies for amphibians and squamate reptiles. This review suggests that (1) repeatabilities for amphibians are generally lower than for squamates, and (2) in all cases, repeatability of locomotor performance declines over time. These results emphasize the necessity of multiple measurements over long time intervals to quantify lifetime performance profiles accurately.