Ph.D. Hinojosa-Toledo, Ivan

Understanding animals' daily activity patterns such as foraging and resting is key to the effective conservation of individuals, populations, and species. Expanding habitat usage by humans today is likely one of the major factors influencing animal habitat use and behavior. Rapa Nui, a remote Chilean island located at the easternmost corner of the Polynesian Triangle, hosts a population of green turtles, Chelonia mydas, that have been monitored by citizen scientists since 2010. Through the collaborative work of divers from the local community and professional scientists, we describe C. mydas daily underwater resting and foraging patterns in Rapa Nui. We identified 15 individuals by monitoring 19 specific resting locations within the Rapa Nui coral reef. A high level of spatial fidelity for specific resting sites was observed in 12 turtles that used the same location for as long as 5 yrs. Moreover, we observed a clear temporal pattern in the daily use of resting habitats, with 79% of resting activity occurring during low tide. In contrast, the daily peak in feeding activity was associated with high tides. Abiotic characteristics (depth and cardinal orientation) of resting sites did not show significant relationships. The information from this study will inform management of the Rapa Nui Multiple Uses Coastal Marine Protected Area to increase the protection of marine turtles residing at this isolated Pacific Island.

1. On shallow reefs, day‐night activity patterns between fishes and invertebrates are presumed to reflect trade‐offs between feeding and predation; however, quantitative data on daily community dynamics are scarce. Moreover, night surveys may contribute important information for biodiversity inventories or baselines that normally are not considered. 2. This study used standardized day–night visual surveys of fishes and mobile invertebrates on the same transect lines in Rapa Nui (Easter Island) and investigated how diel patterns vary between taxonomic and trophic groups. 3. Distinct differences between taxonomic groups were observed, with fishes being more abundant during the day (>twice), whilst invertebrate abundance and richness showed an opposite trend with higher numbers at night (>three times). 4. Analysis of trophic groups showed that herbivorous and planktivorous fishes were more abundant during the day. Carnivorous fishes did not show any trends. Top predators (Apex) were observed only at very low abundances. However, a replacement amongst carnivorous fish species between day and night was found, where labridae fishes were practically absent during nights. 5. Most of the mobile invertebrates remained concealed during the day, probably due to the influence of predation risk (labrid fishes). The results emphasize the need for consideration of nocturnally active invertebrates in biodiversity inventories or baselines of reefs, which focus heavily only on diurnal surveys. 6. Day–night reef surveys should be included in marine protected area planning and monitoring as this provides a better understanding of shallow benthic communities and helps inform proper management decisions.