Seasonal Dietary Patterns of the Mexican Fringe-Toed Lizard (Uma paraphygas)

Abstract

We studied the seasonal dietary patterns of the Mexican fringe-toed lizard (Uma paraphygas) in sand dunes of the Bols6n de Mapimi, Chihuahua, Mexico. Stomach contents were examined and an Importance Value (IV = relative abundance + relative volume + constancy of prey) was determined. We found that formicids were the most abundant prey during spring, summer, and winter, while hemipterans were predominant in autumn. Other abundant food items were lepidopteran larvae (summer and autumn), and isopterans (winter), although seasonal variation existed. This lizard showed a high food niche breadth both for proportion of individuals (x H' = 0.82) and for proportion of the volume prey (x H'v = 0.84) in all seasons and therefore is considered to have a generalist diet. The sexes overlapped in IV throughout the year (Ojk x = 0.88). There were significant differences in morphometric characteristics between main in- sect prey items used throughout the year. However, only coleopteran's length is correlated with SVL (r = 0.53), and both sexes are capable of eating prey much larger than the mean size of prey found in stomachs. Sexual selection is suggested as the probable cause of the difference in body size between sexes. During the breeding season (winter and summer) males concentrated on plants (IV = 62.1 males and IV = 9.7 females for winter, and IV = 61.0 males and IV = 43.2 females for summer), probably reduced their for- aging time, and thus increased the time available for other activities.