We investigated the mechanistic basis for the observed correlation between leg length and perch size among West Indian Anolis lizards by testing the hypothesis that species use those perches upon which they can move most effectively. We used four Anolis species which differed in leg length and perch use in nature. We measured maximum sprint speed on rods of several sizes. Longer-legged species ran faster on thick rods. The speed of all species declined on thinner rods, but long-legged species were affected to a greater extent in that all species ran at approximately the same speed on the smallest rod. The short-legged A. valencienni experienced much less difficulty moving on thin rods than did the other species. Variation in leg length among Anolis might thus represent an evolutionary trade-off between maximizing sprint speed and maximizing stability on thin perches.

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