Effects of brodifacoum on the land crab of Ascension island

Ascension island and its surrounding islets and seastacks form the most imp ortant breeding place for seabirds in the tropical Atlantic. As a result of human exploitation and introduced predators, -populations of most seabirds have undergone large-scale declines since the island's discovery; by human s hi 1501. Plans to restore Ascension's seabird colonies have included prop osals to eradicate the introduced rats using island-wide application of the anticoagulant rodenticide brodifacoum. Assessment of the feasibility of ro dent eradication on this scale requires careful evaluation of the potential non-target effects. We investigated the direct effects of brodifacoum upon the native land crab (Gecarcinus lagostoma), brodifacoum persistence and d istribution in crab tissues, and the potential for secondary effects upon l and crab scavengers and predators, including humans. Land crabs were fed Ta lon pellets (20P and 7-20, 0.002% brodifacoum) to simulate maximum exposure should an island-wide rodent eradication program take place. Crabs were ke pt caged in their natural environment for varying periods of time, and body parts were analyzed for brodifacoum residues. No crabs appeared to die as a result of exposure to brodifacoum. Whilst crabs readily ingested Talon pe llets, only low concentrations of brodifacoum were found in their bodies af ter exposure (less than or equal to 0.129 ug/g wet body tissue). Brodifacou m uas not detected within crab claws at any time, and no residues were dete cted in any body tissues 1 month following exposure.