Chemical signals in desert lizards: Are femoral gland secretions of male and female spiny-tailed lizards, Uromastyx aegyptia microlepis adapted to arid conditions?

Many lizards use femoral gland secretions in intraspecific chemical communication, but specific compounds have been identified in only a few species. Chemical composition of secretions may depend on phylogeny, but it may also evolve to maximize efficacy of signals in a given environment. In deserts, the extreme dry and hot environmental conditions are hostile for chemical signals and, therefore, we expected desert lizards to have secretions with highly stable compounds. Using GC-MS, we identified 74 lipophilic compounds in femoral secretions of male and female spiny-tailed lizards, Uromastyx aegyptia microlepis (Fam. Agamidae), from the Qatar desert. Compounds included mainly steroids and fatty acids, but also terpenoids, ketones, tocopherol, aldehydes and alcohols. We found differences between males and females; males had higher proportions of fatty acids and tocopherol, but lower proportions of ketones than females. Contrary to expectations, the most abundant compounds were not stable in the desert climatic conditions at the surface. However, secretions could be rather adapted to microclimatic conditions inside burrows where these lizards spend long periods of time. We suggest that in addition to phylogenetic and environmental characteristics, we should know the ecology of a lizard species before making generalizations on the potential characteristics of its chemical signals.