Eradicating introduced mammals from a forested tropical island

Methodologies developed in New Zealand for eradication of exotic mammals from temperate oceanic islands were adapted for use on a topographically complex, 194-ha, densely forested, tropical island off the Pacific coast of Mexico. Isla Isabel is a National Park and a nesting refuge for nine species of marine birds, but the island’s extraordinarily dense population of cats (113/k2) was annually killing 23–33% of nesting sooty terns. We provide quantitative descriptions of the implementation and outcome of the methodologies over a period of three years, culminating in successful eradication of cats, but not rats. We also provide quantification of the effects of cat eradication on sooty tern mortality over a period of 11 years.