Locomotor performance and dominance in male Tree Lizards, Urosaurus ornatus

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Abstract

1. The importance of locomotor performance to the social status of male lizards may lie in its effect on the outcome of agonistic interactions and territorial contests. Presumably, dominant males are able to acquire and defend larger territories, encounter more potential mates and have greater reproductive success.

2. Therefore, the hypothesis that dominance status should covary with locomotor performance was tested using the Tree Lizard, Urosaurus ornatus.

3. Two components of locomotor performance, maximum sprint speed and stamina, in males were measured. The former variable was estimated as the fastest speed on a 0·25-m length along a 2-m long racetrack. The second variable was measured as the elapsed time a lizard could sustain a walking pace on a canvas belt moving at 0·50 km h−1.

4. The relative social status of size-matched males was independently determined by staging paired encounters in a novel arena. Dominance was measured by behavioural scores of aggression and submission.

5. The dyadic encounters resulted in the unambiguous determination of dominant individuals for 48 of 50 trials. Dominant males were significantly faster than submissive males. In addition, endurance capacity of dominant males exceeded the submissive males.

6. Dominance behaviour and locomotor performance are strongly associated. Although the exact underlying mechanism is unknown, the results suggest a link between hormones, performance and behaviour in territorial lizards.

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