However the survivors still managed to breed up to a population of 300 million by 1995. The best and most humane long-term option to reduce populations is fertility control to stop breeding. There are many colonies of unowned cats around human settlements. Cats are very prolific breeders and these populations can expand to the point where the animals are unhealthy and a nuisance. People in the area can be disturbed by the fighting, spraying and caterwauling of the undesexed colonies.
Authorities then try to eradicate the cats, sometimes by cruel methods.
However, it is very unlikely that every single cat will be removed, and it only takes one breeding pair to re-establish the population. In addition, when an area is vacant, other cats will move in to claim the territory. The killing has to start all over again, ad nauseam. By 1975 there were 2,500 cats on the island preying on ground-nesting seabirds. Between 1986 and 1989 further surviving cats were exterminated by hunting.