Friday January 6, 2023
Earth.com —
Rats have been introduced to many offshore islands in the past, mostly arriving by accident aboard visiting ships. They can cause devastation to the indigenous wildlife of these islands, particularly if the native species include ground-nesting birds. This has led to a call for rat eradication programs on many islands, in order to save wildlife from the deleterious impacts of these introduced rodents.
A study led by researchers at Lancaster University has now identified an unexpected way in which invasive rats on tropical islands have affected the lives of fish inhabiting the reefs around the islands. This is an unusual instance where the presence of terrestrial rats leads to a change in the behavior of species in an entirely different biome. It reveals how species in different biomes are linked, despite the fact that they will never meet one another.
The study, which also involved researchers from Lakehead University in Canada, compared the territorial behavior of jewel damselfish (Plectroglyphidodon lacrymatus) on reefs around five rat-infested and five rat-free islands in a remote archipelago in the Indian Ocean. These small reef fish are highly territorial and readily chase away other fish that enter their territory. They “cultivate” patches of algae between the branches of corals within a territory, and mostly direct their aggression towards intruders that are also herbivorous and in search of algal turf for food.