摘要：IN 2002, DAILY AND SEASONAL ACTIVITY PATTERNS OF THE LIZARDS UTA STEJNEGERI, UMA EXSUL, AND ASPIDOSCELIS MARMORATA WERE EVALUATED IN A DUNE HABITAT IN THE SOUTHWESTERN PORTION OF COAHUILA, MEXICO. METHODS INCLUDED SURVEYING A 500 M TIVITY PATTERNS OF THE LIZARDS UTA STEJNEGERI, UMA EXSUL, AND ASPIDOSCELIS MARMORATA TRANSECT ONCE PER HOUR BETWEEN 0700 AND 1900 FOR 7 DAYS EACH SEASON DURING THE SPRING, SUMMER AND FALL. THE NUMBER OF ACTIVE LIZARDS, AIR AND SUBSTRATE TEMPERATURES, AND RELATIVE HUMIDITY WERE RECORDED. A STANDARDIZED LEVINS INDEX AND PIANKA´S METHOD WERE USED TO MEASURE TEMPORAL NICHE BREADTH AND OVERLAP, RESPECTIVELY. IN EACH OF THE 3 SEASONS, U. STEJNEGERI WAS ACTIVE EARLIER THAN U. EXSUL, AND U. EXSUL WAS ACTIVE BEFORE A. MARMORATA. THE 3 SPECIES SHOWED A BIMODAL ACTIVITY PATTERN DURING SPRING AND SUMMER, AND UNIMODAL IN FALL. ASPIDOSCELIS MARMORATA SHOWED THE SMALLEST NICHE BREADTH IN THE 3 SEASONS. FOR EACH SPECIES, PREFERRED BODY TEMPERATURE AND ENVIRONMENTAL TEMPERATURE SEEM TO DICTATE ACTIVITY PATTERNS OF THIS LIZARD GUILD AT VIESCA.
