Back in 2002, Ascension Island which is a UK Overseas Territory, had its cat population eradicated by the RSPB. Fast forward 14 years and they now have another population crisis- rats.
Over a two year period, all cats living in the wild were either destroyed or poisoned, which helped increase the numbers of endangered Frigate Birds and Masked Boobies. The process, which received funding from the Foreign and Commonwealth Office, had the aim of removing the predatory cats to allow the falling bird numbers to flourish.
However, without the cats preying on rats, the rodents numbers have risen sharply. These rats have now taken to eating the eggs and young Sooty Tern Chicks.
Dr. Jim Reynolds of the University of Birmingham explains, ““There was a problem with domesticated cats escaping from human settlements and going feral and decimating seabirds, but after the 2002 programme there was a very successful recovery of frigate birds and boobies.
“But since then we’ve noticed an explosion in rat populations. The removal of an apex predator has allowed a mesopredator to thrive. And they are moving away from the mountains towards where the seabird colonies are breeding.”
Removing the cats has had the desired effect with increasing Frigate and Masked Boobies numbers, however it has encouraged the rats to prey on the Terns which has now started to decrease their population.
Jonathan Hall, our Head of Overseas Territories, said: “The rat problem is certainly something we are trying to look into at the moment.
“There isn’t solid evidence about the level of rat predation or population level increases at the moment. But we have carried out rat eradication programmes in the past.”