Ontogenetic and Seasonal Shifts in Microhabitat Use by the Lizard Cnemidophorus sexlineatus

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Abstract
I studied the microhabitat use patterns of adult and juvenile six-lined racerunners, Cnemidophorus sexlineatus, through thermally distinct seasons in southern Oklahoma [USA] from 1982-84. Principal components analysis indicated that juveniles used more exposed microhabitats than adults during most of the year. This was probably due to size-related differences in the biophysical properties of lizards that result in large lizards being at greater risk of overheating in exposed microhabitats. Adult racerunners show non-random microhabitat use during the mild seasons whereas juveniles show non-random microhabitat use during the hottest season. The exposure and thermal qualities of the spectrum of microhabitats potentially available to lizards changes seasonally. Both age classes show a parallel seasonal shift in microhabitat use with respect to thermal habitat parameters but are invariant with respect to exposure. This suggests microhabitat exposure is a more important cue for lizard microhabitat selection than thermal parameters.