Scientists have discovered for the first time that invasive rats on tropical islands are affecting the territorial behaviour of fish on surrounding coral reefs.
The new study, led by scientists from Lancaster University in the UK and involving researchers from Lakehead University, Canada, shows that the presence of invasive black rats on tropical islands is causing changes in the territorial behaviour of the jewel damselfish — a herbivorous species of tropical reef fish that ‘farm’ algae in the branches of corals.
On islands with invasive rats, the rodents attack and eat small resident seabirds and their eggs, decimating their populations to the extent that seabird densities are up to 720 times smaller on rat-infested islands.
This results in a drop-off of nutrients in the seas surrounding rat-infested islands, with 251 times less nitrogen flowing onto the coral reefs around these islands, lowering the nutrient content of seaweed for herbivorous fish.
The study is published in Nature Ecology and Evolution
image: Jewel Damselfish (Plectroglyphidodon lacrymatus) near rat-free islands credit: Dr Rachel Gunn