Ecology of lowland lizards in the eastern United Arab Emirates

Abstract

Aspects of the ecology of 23 lizard species found in the coastal lowlands of eastern Arabia are reported. The majority of these forms occur in arid environments and the most obvious ecological separation is between diurnal and nocturnal species, the ten latter forms all being geckos. Within these two groupings, species differ principally in microhabitat (particularly such features as distance from vegetation and ground softness), hunting techniques (“sit and wait”, active search or slow visual scanning) and the size of their mainly arthropod prey. However, two large diurnal forms are food specialists, feeding largely on plants and small vertebrates, respectively, and some diurnal species show differences in their time of activity during the morning. Body temperature of day‐active species, which are all essentially heliothermic, is controlled by posture, retreat into shade or burrows and the use of the ground as a heat sink. Usual activity temperatures show correlation with normal time of activity during the morning and the amount of shade cover available. Substantial interspecific variation exists in the extent to which body temperature is regulated. Most nocturnal forms have body temperatures close to the ambient but they may sometimes be elevated in Bunopus tukerculatus, perhaps as a result of utilizing underground warmth. A wide range of predator avoidance techniques are used, including fleeing, hiding in burrows, burial in loose sand and caudal autotomy. The proportion of damaged tails is higher in climbing species than in ground‐dwelling ones. Females are mainly gravid in the spring. The number of eggs carried is low in species of small body size (often one or two), suggesting that egg‐laying is repetitive. Contrary to accepted opinion, clutch size is variable in some gekkonine species, either one or two eggs being laid. Hatchlings appear largely in the late spring and summer. A number of morphological features correlate with niche characteristics: gross body shape is related to hunting and escape technique, foot structure to substratum type, and species living on soft sand have modifications that exclude sand from the body orifices. The lizard fauna discussed here extends with only restricted change over much of Arabia. The faunas of the extreme south west of the peninsula and of the Sahara are generally similar to it, but differ substantially in the species they contain, and possibly in the pattern of occupied niches as well.