Behavior and Activity Budgets of Costa Rican Basilisks

Schimmel/Conrades Science Center 161

An organism’s balance between consuming and expending energy can impact fitness. Within a species, individuals exhibit different activity budgets due to dependence on both intrinsic factors (e.g. age, sex, reproductive status) and extrinsic factors (e.g. competition, predation, prey availability, habitat structure, climate). The basilisk lizard (Basiliscus spp.) is known for its peculiar ability to run bipedally across water, a strategy utilized to avoid predators and chase prey. As a sit-and-wait foraging lizard, the basilisk must budget time and energy spent foraging, patrolling territory, mating (basilisks in Costa Rica breed year-round), basking, and scanning for potential predators and competitors. Basilisks were observed in Costa Rica at Pocosol Biological Station for three days (B. plumifrons, one site) and at Hacienda Barú for two days (B. basiliscus, two sites). All individuals were observed during 30 minute periods. During observation periods, movements and responses (or lack thereof) to external stimuli were recorded. All three observed habitats included figs, which may serve as an important food source for basilisks. Juveniles tended to live in pairs or groups whereas adult males of both species were more solitary and exhibited territorial behavior. In the majority of cases, adult males tended to dive underwater as a means of escape. Juveniles were not observed in a wet habitat, so were only observed taking cover under tree roots. Adult males mainly scanned with their eyes whereas juveniles turned their heads and moved around more often. Overall, juveniles were more active than adults; they foraged, scanned, and fled more frequently, possibly because the smaller body size makes them more vulnerable to predation while also allowing them to more quickly reach an active body temperature.