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For: The opinion Updated 06 Jan 2023, 0:22 am EST
For years, rats have become a problem relevant to major cities like New York and now a research reveals that they also affect animal species on tropical islands.
Scientists have discovered for the first time that Invasive rats on tropical islands affect territorial behavior of fish of the surrounding coral reefs.
The new study, led by scientists from Lancaster University (UK), shows that the presence of invasive black rats on tropical islands is causing Changes in territorial behavior of jewel damselfisha herbivorous species of tropical reef fish that “grows” algae on the branches of corals.
The study, published in Nature Ecology and Evolution and involving researchers from the University of Lakehead (Canada), compared five rat-infested and five rat-free islands on a remote island archipelago in the Indian Ocean.
The scientists found that rats, which in many cases they arrived on the islands as stowaways on ships in the 18th centurymodify the behavior of damselfish by disrupting an important nutrient cycle.
The research explains that the seabirds travel to the open sea to feed and return to nest on the islands. These animals deposit nutrients through their droppings on the islands, and many of these nutrients are later washed into the seas, fertilizing the surrounding coral reef ecosystems, where the damselfish feed.
On islands with invasive rats, rodents attack and eat small resident seabirds and their eggsdecimating their populations to the point that seabird densities are up to 720 times lower on rat-infested islands.
This is how rats affect fish
The situation described above causes a drop in nutrients in the seas surrounding the rat-infested islandswith 251 times less nitrogen flowing into coral reefs, reducing the nutrient content of algae for herbivorous fish.
Around islands with intact populations of seabirds, breeding damselfish aggressively defend their small plotusually less than half a square meter, of the reef.
But the scientists found that damselfish that lived on reefs adjacent to rat-infested islands were much more likely to have larger territoriesand five times more likely to behave less aggressively than those living on reefs adjacent to rat-free islands.
Damselfish on rat-infested islands, the study explains, they had to have larger territories (an average of 0.62 m², compared to an average of 0.48 m² on rat-free islands) because the kelp grass on rat-infested islands was less nutrient-dense due to a lack of bird-derived nutrients marine.
“We believe that the presence of rats is reducing the nutritional benefit of the lawn to the point where it’s almost not worth fighting for, which is what we’re seeing with these behavioral changes,” said Dr. Rachel Gunn, who conducted the research as part of her doctoral studies at the University from Lancaster and who now works at the University of Tübingen (Germany).
The study adds to the evidence base supporting the need to eradicate rat populations Invaders of tropical islands.
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