The behavioral ecology of sleep: Natural sleeping site choice in three Anolis lizard species

Where animals sleep may be an important component of their behavioral ecology, as sleeping renders animals immobile and hypothetically vulnerable for long periods. Yet, sleep is rarely studied outside of the laboratory. To investigate factors that influence natural sleeping behavior, we examined sleeping locations of three sympatric species of territorial Anolis lizards (Anolis lineatopus, A. grahami and A. valencienni) that have evolved adaptations to different microhabitats. Results indicate that sleeping perch differences among these species are consistent with their diurnal specializations, and sleeping perches are generally higher, narrower, and more horizontal than diurnal perches. We find only limited evidence for sleeping site fidelity; although individuals of one species have apparent sleeping areas within their home ranges, few lizards repeatedly sleep on perches within 0.5 m of previous sleep perches. In a closer examination of the sleeping sites of A. lineatopus, we find that male nocturnal ranges are more dispersed from conspecific males than their diurnal ranges, and they typically sleep near their territory boundaries. We conclude that while Anolis sleeping site choice is strongly influenced by diurnal behavior (including territorial defense and microhabitat choice), differential diurnal and nocturnal microhabitat use may result from differing pressures during day and night.