pest control

Predation by introduced mammals is considered a primary threat to New Zealand’s native frog populations. Rats are known predators of the terrestrial Archey’s frog (Leiopelma archeyi), New Zealand’s smallest Leiopelmatid frog. During a 12 year study in Whareorino Conservation Area, we investigated effects of sustained rat control on survival, number of independent juveniles per adult, and abundance of Archey’s frog. Frogs were monitored following a capture-recapture robust design at four grids, split between a 300-ha ‘nontreatment’ area and a 300-ha rat control ‘treatment’ area.

To test the long-term efficacy of mammalian pest control, annual distance sampling estimates of the density of North Island kākā (Nestor meridionalis septentrionalis) within the southern Waipapa Ecological Area (WEA), Pureora Forest Park from 2008–2020 are compared to previously published estimates made at the same sites and time of year (October) between 2000–2007. Kākā density increased approximately four-fold from an average of c. 0.5 (95% CI 0.5–0.6) birds ha⁻¹ between 2000 and 2007 to c. 2.3 (95% CI 1.9–2.8) birds ha⁻¹ in 2020.

Benefits of invasive species management for terrestrial biodiversity are widely expected and promoted in New Zealand. Evidence for this is presented in policy and scientific reviews of the literature, but the robustness and repeatability of the underpinning evidence-base remains poorly understood. We evaluated the design of field-based studies assessing biodiversity responses to invasive species management in 155 peer-reviewed articles published in 46 journals from 2010–2019.

In New Zealand, ship rats (Rattus rattus) have been implicated in many extinctions, declines, and range contractions of native birds, so ship rats are an important target of predator control. The outcomes of ship rat control operations are difficult to predict due to other factors which affect rat populations including altitude, Nothofagus seedfall, and control of other mammalian pests, particularly brushtail possums (Trichosurus vulpecula) and stoats (Mustela erminea).

The endemic fauna of New Zealand evolved in the absence of mammalian predators and their introduction has been devastating. Large-scale aerial applications of cereal baits containing sodium fluoroacetate (1080) are routinely used to control these pests. During one such operation in the Blue Mountains, West Otago, trail cameras were used to monitor the impact of the application on mammalian predators.

The impact of aerially applied 1080 poison on a Western weka (Gallirallus australis australis) population was assessed at Tennyson Inlet, Marlborough Sounds, between September 2010 and June 2016. We estimated mortality and the incidence of sublethal poisoning as a direct consequence of two aerial 1080 operations and examined the differences in nest success, chick survivorship and adult survivorship. Most weka in the treated block appear to have been sublethally poisoned but only one of 58 (1.8%) radio-tagged weka died as a direct consequence of 1080 application.

The kea (Nestor notabilis) is a highly intelligent and adaptable omnivorous New Zealand parrot. These traits potentially put kea at risk of poisoning during vertebrate pest poisoning operations. However, as kea fall prey to introduced pests, they also gain from pest control, creating a cost-benefit situation.

Controlling rodents near municipal areas requires bait that must be housed in purpose-built bait stations to prevent interference from curious people, companion animals, and non-target species. Bait station design is important, but so are the baits themselves.

We used a long-term replicated before-after control-impact (BACI) sampling design to monitor the effect of aerial 1080 possum-control operations on common forest bird populations. Paired treatment and non- treatment sites in the Rolleston Range (East Coast, South Island) and Alexander Range (West Coast, South Island) were monitored once before 1080 treatment during winter 2012 and for three successive summers afterwards. Mammals (possums Trichosurus vulpecula, rats Rattus spp.

In New Zealand, aerial poisoning with 1080 (sodium fluoroacetate) bait is widely used for control of introduced small mammal pests in remote or forested areas. However this practice is controversial, partly because of perceived risks to native fauna, particularly birds. That perception originally derives from substantial mortality of some native bird species in pre-1980 control operations, which prompted changes in baiting practice to mitigate most of the risk.