Black rat (Rattus rattus) captured in a fur seal rookery at Guafo Island. © Mauricio Seguel

Biological invasions are one of the greatest threats to biodiversity in the world. Among invasive mammal species cats and rats have been identified as two of the most pernicious species, especially in oceanic islands since native fauna from those places evolved in absence of land predators.

Guafo Island is an inhabited island and one of the most important biodiversity hotspots at the Pacific Patagonia. In this place avian, native small rodents and marine mammal species live in contact with introduced rat and feral cat populations.

Pathogens are natural enemies that can potentially regulate their host populations (e.g. rats). Introduced rats can loss some critical, population-regulating pathogens during the process of invasion, and may not have as many natural enemies as in mainland, leading to increased densities and facilitating the establishment and maintenance of their populations (enemy release hypothesis). If this is the case, new introductions would have a negative effect in the established group and an advantage for the new invaders, making it easier for other invasive species (e.g. Rattus nonvergicus, Mustela vison) to establish on the Island. Because of this this project will measure the parasitic diversity, density and distribution of rat populations.

Additionally as a result of trapping in different sites along Guafo Island coast, we can determine rat presence or absence, and estimate through capture success the density of their subpopulations.

Through determining the presence of Taenia taeniformis cysts in rat livers (a cestode that requires a felid final host), we can assess the presence of cats in the area. This is really important since we think that areas of the island with sporadic human intervention (fishermen campsites) could be one of the sources of new mammal invasions and one of the spots with higher rat density, and higher parasitic diversity.

Through our field work in key places with human activity, and a current project of extension in local schools we intend to involve local communities in this project and help them avoid new introductions of non-native species to the island.