Costa Rica News – Almost 500 years ago rats first arrived on Cocos Island along with the first boats.
Aside from eating the endemic species, they go after the white tern, also called the Holy Spirit bird. This species, while not endemic, uses Cocos Island as its sole nesting site in the Eastern Tropical Pacific.
There is a fear that these birds and other at risk species, such as an endemic lizard, may go extinct due to the high population of rats going after them. The rats also eat insects, mollusks, crustaceans and fish. The waste created by rats affects the water supply for people living on the island.
The rats have a healthy gene flow, making reproduction easy. They are also good swimmers, colonizing the nearby Manuelita Island.
For this reason, in order to control the rat population there needs to be a ban on fishing vessels and tourist boats which bring more rats and make the population and gene pool stronger.