Invasive rats reshape reef food webs in the Chagos Archipelago

Scientists from Lancaster University and the University of Texas found that invasive black rats on islands of the Chagos Archipelago dramatically alter nearby coral reef ecosystems. By preying on seabird eggs and chicks, the rats suppress seabird colonies, cutting the flow of nutrient‑rich guano that fertilises surrounding waters. Without this input, reefs adjacent to rat‑infested islands host a higher proportion of small invertebrates and far fewer cryptobenthic fish such as gobies and triplefins, whose biomass can be more than five times lower than on rat‑free islands.

The shift in the reef’s base community can ripple up the food web, affecting larger fish and the overall resilience of the coral ecosystem. The researchers suggest that eradicating invasive rats and protecting seabird populations could restore natural nutrient cycles and help maintain healthy reef food webs.