Recovery of introduced Pacific rats following a failed eradication attempt on subtropical Henderson Island, South Pacific Ocean

A failed eradication attempt of Pacific rats (Rattus exulans) on Henderson Island, a UNESCO World Heritage Site in the South Pacific, led to rapid population recovery within two years. The study found annual per capita growth rates ranging from 0.48 to 5.95, with rat numbers rebounding from 60–80 individuals to two-thirds of pre-eradication levels before stabilizing around carrying capacity. Seasonal fluctuations in trapping rates—peaking at 36.6 rats per 100 trap-nights and dropping to 12.6—were observed, alongside density variations (20.4 to 42.9 rats/ha) in embayment forests and lower densities (0.76 to 6.08 rats/ha) on coral plateaus. These findings highlight the challenges of rodent eradication in tropical environments, where reduced seasonality and resource pulses complicate population dynamics. Understanding invasive species behavior is critical for future eradication success.

Veitch, C. R., Clout, M. N., Martin, A. R., Russell, J. C., & West, C. J. (Eds.). (2019). Island invasives: scaling up to meet the challenge. Proceedings of the international conference on island invasives 2017. https://doi.org/10.2305/iucn.ch.2019.ssc-op.62.en