Main Objectives
This project aims to understand how the loss of terrestrial crabs affects forest ecosystems on Tetiaroa Atoll. By simulating their absence using 3x3 meter exclosures installed in coconut and broadleaf native forests, researchers seek to measure changes in vegetation, soil nutrients -particularly carbon and nitrogen - and invertebrate communities. The goal is to demonstrate the critical role of crabs as bioturbation agents and nutrient vectors between marine and terrestrial systems, and to position them as a conservation lever for atoll ecosystems.
Field Actions and Preliminary Results
In July 2025, Charles Braman and his team continued a study initiated in 2024 across several motu - Tiaraunu, Rimatu’u, Reiono, and Oroatera -installing and monitoring exclosures designed to exclude crabs. Trail cameras were deployed at 12 sites to monitor crab activity, while soil and leaf samples were collected to analyze shifts in carbon and nitrogen isotope signatures. Soil carbon flux robots (fluxbots) were installed inside and outside exclosures to track real-time carbon exchange. Ten-meter transects were used to map crab burrow density, and GPS units traced colony boundaries.
Early results suggest that crab absence alters plant composition - particularly by favoring rare species they typically consume - and reduces nutrient availability in the soil. These observations confirm that crabs are key drivers of soil fertility and forest ecosystem dynamics.
Perspectives
The project will continue through 2027, with annual monitoring to assess long-term exclosure effects. Data will be analyzed in the United States and shared with the Tetiaroa Society to integrate crab management into atoll conservation strategies. Collaboration with The Brando staff is planned -particularly for monthly exclosure checks and data collection -to strengthen local involvement and project sustainability.
This work contributes to a broader understanding of terrestrial crabs’ role in Pacific island ecosystems -often overlooked compared to seabirds. It reinforces the Tetiaroa Society’s mission by identifying crabs as a pillar of atoll ecological resilience.