Introduced black rats are among the most invasive species to islands worldwide. In addition to agricultural impacts,rats are vectors of disease, cause damage to native flora and fauna, and negatively impact threatened/endangered species.Eradication efforts have met with mixed success. Success or failure of an eradication effort can depend on the population density ofthe target species, which can influence rodenticide sowing rates. We used snap trapping grids to estimate black rat densities in twodifferent forest types on Diego Garcia: coconut forest and mixed species forest. Individual snap traps baited with fresh coconutwere placed every 10 m in a 100-m × 100-m (1 ha) grid in the mixed forest and every 20 m in a 220-m × 220-m grid (4.8 ha) in thecoconut forest. Traps were checked twice daily for 7 and 11 days in the mixed and coconut forest, respectively. In total, 914 ratswere captured on the coconut forest grid and 125 rats were captured on the mixed forest grid. Rat density in coconut forest was 187rats/ha (95% CI: 176-201) and 88 rats/ha (95% CI: 82-104) in mixed forest. Stomach contents were examined in 121 rats trappedin the mixed forest: 81% contained coconut along with other vegetation or meat, and 67% contained coconut exclusively. It islikely that the high rat density is driven by an abundant coconut food source resulting in a variable distribution of rats among habitattypes. Planning for eradication will need to consider the variability of rodent densities across different habitats, with managementstrategies developed to address this variability
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Vogt, S., Vice, D., S., Pitt, W., C., Guzman, A., Nestor, Necessario, E., J., & Berentsen, A., R. (2014). Rat Density on Diego Garcia: Implications for Eradication Feasibility. Proceedings of the Vertebrate Pest Conference, 26. https://doi.org/10.5070/v426110559
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