Introduced mammalian predators are responsible for the decline and extinction of many native species, with rats (genus Rattus) being among the most widespread and damaging invaders worldwide. In a naturally fragmented landscape, we demonstrate the multi-year effectiveness of snap traps in the removal of Rattus rattus and Rattus exulans from lava-surrounded forest fragments ranging in size from <0.1 to >10 ha. Relative to other studies, we observed low levels of fragment recolonization. Larger rats were the first to be trapped, with the average size of trapped rats decreasing over time. Rat removal led to distinct shifts in the foraging height and location of mongooses and mice, emphasizing the need to focus control efforts on multiple invasive species at once. Furthermore, because of a specially designed trap casing, we observed low non-target capture rates, suggesting that on Hawai‘i and similar islands lacking native rodents the risk of killing non-target species in snap traps may be lower than the application of rodenticides, which have the potential to contaminate food webs. These efforts demonstrate that targeted snap-trapping is an effective removal method for invasive rats in fragmented habitats and that, where used, monitoring of recolonization should be included as part of a comprehensive biodiversity management strategy.

The Seychelles black parrot Coracopsis (nigra) barklyi, endemic to the Seychelles islands, is the only surviving parrot on the archipelago. Although originally classified as a subspecies of the lesser vasa parrot Coracopsis nigra evidence now indicates that the Seychelles population may be a distinct species, in which case its conservation status also requires reassessment. Here, we address the status of the C. (n.) barklyi population on the islands of its current and likely historical range, Praslin and Curieuse, assess the effect of habitat type on relative abundance, and identify the most appropriate point count duration for monitoring the population. We conducted point count distance sampling at 268 locations using habitat type as a covariate in the modelling of the detection function. Density on Praslin was estimated to be 0.14–0.24 individuals per ha, resulting in an estimate of a total of 520–900 individuals (95% confidence interval). The highest densities occurred in endemic palm and mixed forests. Habitats with a high proportion of palms were more likely to support parrots than habitats without palms. As no parrots were detected on Curieuse the number estimated on Praslin is the global wild population. The small size of this population necessitates its categorization as Vulnerable on the IUCN Red List. Our main recommendation for the conservation of C. (n.) barklyi, in addition to continued monitoring, is the preservation and expansion of the parrot's endemic palm forest habitat.

Removing invasive rats from islands is a powerful conservation tool, and practitioners are now targeting larger islands for rat eradication. As they do so, they face the challenge of mitigating for potential non-target impacts on native biodiversity that may be susceptible to rodenticides. We report on the eradication of black rats Rattus rattus from Anacapa Island, California, in 2001–2002, which was the first-ever invasive rodent eradication from an entire island where an endemic rodent was present and the first aerial application of a rodenticide in North America. As a mitigation strategy we staggered the rodenticide application over 2 years and held a representative sample of the Anacapa deer mouse Peromyscus maniculatus anacapae in captivity. We also mitigated for bird species potentially susceptible to brodifacoum poisoning and monitored aspects of the terrestrial and marine environments. The free-ranging native rodent population severely declined following rodenticide applications but reintroduction and translocation efforts were successful, and the population quickly recovered to pre-eradication levels. Non-target impacts also included mortality of raptors, gulls and passerines, including high mortality of rufous-crowned sparrows Aimophila ruficeps obscura despite planned mitigation. All observed non-target impacts are expected to be ephemeral; however, further monitoring should reveal details on the dynamics of those impacts. Brodifacoum was not detected in the marine environment or in significant amounts in terrestrial soil, plants and arthropods. Seabird benefits from the rat eradication were quickly realized.