The Editor’s Choice for Issue 54:1 is written by Associate Editor Ayesha Tulloch. The article chosen by the Editors as this issue’s Editor’s choice article is ‘Optimizing confirmation of invasive species eradication with rapid eradication assessment‘ by James Russell and colleagues.

Invasive species are one of the leading causes of biodiversity declines and extinctions globally. Efforts are increasing around the globe to manage and in many cases attempt to eradicate introduced plants and animals. Examples include the Australian “National Four Tropical Weeds Eradication Program”, and “Predator-Free 2050”, the New Zealand Government’s vision to eradicate all invasive predators by 2050.

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Cumulative number of successful invasive mammal eradication projects by year since 1950. Data are restricted to whole island events, excludes reinvasions, and data quality scored as good or satisfactory only. (Source: http://diise.islandconservation.org/)

New advances in eradication techniques are constantly emerging, with many recent successes attributed to novel methods of detecting cryptic or inaccessible invasive populations, through the use of sniffer dogs and unmanned drones. Confirmation of invasive species eradication following management typically occurs after waiting an arbitrary period of time before determining success or failure based upon the presence or absence of the target species (the so-called “Wait-and-See” approach). The risk of this approach is that it does not facilitate rapid response to early detection of survivors and thus obligates repeating costly and time-consuming eradications from scratch.

Along with advances in eradication, land managers faced with introduced predators therefore need cutting-edge scientific tools to enable them to confirm eradication as quickly as possible so they can move on to the next project without wasting limited resources on unnecessary monitoring and management. The recent study by Russell et al. has made significant progress towards addressing this need through the development of a new online tool for rapidly confirming when pests have been successfully eradicated from an area. Their rapid eradication assessment (REA) tool is an alternative to the traditional “Wait-and-See” approach, and requires the eradicated areas to be monitored using a grid of detection devices at some fixed time soon after eradication. The REA tool then builds statistical models of the probability of detecting survivors and their offspring, and estimates the probability that an eradication operation is successful given that no pests are detected during the monitoring sessions (Samaniego-Herrera et al. 2013).

This pioneering work is a collaboration between academics from the University of Auckland Department of Statistics and School of Biological Sciences, and scientists and on-the-ground managers from Landcare Research (New Zealand) and GECI (Grupo de Ecología y Conservación de Islas, Mexico). Users input basic population dynamic parameters for the pest species, such as how far individuals can move, how likely they are to be detected, and what level of effort will be put into monitoring. The software (freely available from http://www.rea.is) calculates the likelihood that pests have been eradicated from the area if none are detected during follow-up surveillance.

The software also allows users to simulate different monitoring scenarios which would maximise the confidence in confirming eradication success, e.g. over 95%. Russell et al. demonstrate the tool using real data on the eradication of house mice Mus musculus from the Mexican ‘Island of the Dead’ (Isla Muertos), and show how to calculate the probability that the mouse control efforts on the island in 2011 have led to successful eradication of this species. Mice are an ideal case study for this tool as they have severe impacts on native ecosystems, in particular, islands with no other mammals present (Angel, Wanless & Cooper 2009), and eradication attempts do not always meet with success. This is because mice are difficult to detect at low densities (Nathan et al. 2013), and they are rapid recolonizers (Nathan et al. 2015).

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Mus musculus fitted with tracking device.

Controlling invasive pests is a massive challenge worldwide, with even a single eradication of some pests costing billions of dollars (Pimentel et al. 2000). The approach developed by Russell et al. facilitates early detection and removal of localised survivors to avoid complete repeats of eradication operation when survivors are not detected and increase to unsustainable levels again. REA can also be used prior to confirmation to simulate different monitoring regimes (e.g. number of devices, number of nights, time since eradication) to optimise the level of effort required in confirming eradication to a given probability. By confirming eradications faster managers can move more quickly to eradications of other species, species reintroductions, and eventual ecosystem restoration and recovery.

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The native bird species on Isla Muertos are in peril from introduced house mice that predate on seabird eggs and chicks (Cuthbert et al. 2004)

Read the full article here:

Russell, J. C., Binnie, H. R., Oh, J., Anderson, D. P., Samaniego-Herrera, A. (2016), Optimizing confirmation of invasive species eradication with rapid eradication assessment. Journal of Applied Ecology. doi: 10.1111/1365-2664.12753

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