Eradicating invasive rodents from wet and dry tropical islands in Mexico

Abstract

AbstractEradications of invasive rodents from tropical islands have a lower success rate compared to temperate islands. In the tropics the wide range of physical and biological conditions results in a wide variety of island biomes, with unique challenges and windows of opportunity for rodent eradications. We describe and compare research and operational details of six successful eradications of invasive miceMus musculusand ship ratsRattus rattuscarried out during 2011–2015. The work was conducted on six islands in two distinct tropical archipelagos in Mexico (one dry in the Gulf of Mexico; one wet in the Caribbean), and included the first eradication of rats from a mangrove-dominated island > 500 ha. Invasive rodent populations varied among species and islands, even neighbouring islands; overall density was higher on wet islands. Physical and biological features, including the presence of land crabs, determined eradication timing and rates of bait broadcast (higher on wet islands). An interval of 6–10 days between the two bait applications per island was sufficient to eradicate actively breeding mouse and rat populations. Impacts on non-target species were negligible, including those on wild and captive iguanas. Eradication success was rapidly confirmed based on ground monitoring and statistical modelling. Rodent eradications on larger tropical islands should be achievable with directed research to inform planning and implementation.