Effects of Reduction in Windblown Sand on the Abundance of the Fringe-Toed Lizard (Uma inornata) in the Coachella Valley, California

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Abstract
The habitat of U. inornata consists of solely of windblown sand deposits in the Coachella Valley, Riverside County, California. Densities of this lizard in ten 2.25-ha plots were estimated by capture-recapture analysis during the spring and summer of 1980. Six plots were arranged in pairs, with 1 member of each pair in apparently undisturbed habitat upwind of a tamarisk windbreak and the other member downwind of the obstruction. The other 4 plots were in areas with sandy hummocks or mesquite dunes. The abundance of Uma varied in different plots, ranging from as high as .apprx. 45 ha-1 to zero. The 3 plots of downwind of tamarisk windbreaks where sand depletion and surface stabilization have been underway for a number of years were essentially unoccupied by Uma. The upwind plots supported densities ranging from 11-45 ha-1. Variations in abundance of Uma were not statistically correlated with individual physical attributes of sand. By focusing on the quality of sand in dunes on the lee sides of shrubs 2 models relating to densities of Uma were developed. Variables of interest were: penetrability of sand in lee areas, surface coarseness, diameter of sand grains at the 75th percentile of graduation by weight and years since surface stabilization. Both models explained about 81% of observed variation in Uma densities. Increased sand penetrability is a positive environmental factor and surface coarseness a negative one. Increasing surface stabilization is reasoned to be detrimental to Uma. Methods of capture-recapture analysis used in this study sometimes resulted in unsatifying upper bounds of confidence intervals for density estimates. Further density estimates should be derived from analyses of a chain of at least 3 samples.

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