1080

Understanding rates of reinvasion is critical for determining what drives ship rat population recovery following large-scale control operations. We radio-tracked 23 adult ship rats on the edge of a forested area where rats had been suppressed by aerial compound 1080 in the Hollyford Valley, Fiordland. Eleven individuals died within two months of collaring and two individuals were never detected again, leaving us with data from 10 rats.

A resetting toxin device (the “Spitfire”) has been designed that delivers a toxic paste to a rat’s ventral surface when it passes through a tunnel. The rat grooms off the paste and ingests the toxin. The system was assessed in cage trials and one field trial. The purpose of the cage trials was to investigate whether a range of toxins can be delivered by the Spitfire to rats (Rattus rattus and R. norvegicus), namely 0.55% sodium fluoroacetate (1080), 0.2% brodifacoum, 15% cholecalciferol, and 12.5% zinc phosphide.

The introduction of mammalian predators, particularly stoats (Mustela erminea), to New Zealand led to the decline in whio (Hymenolaimus malacorhynchos), an endemic riverine duck. Stoat control for whio in the South Island has focused on valley floor trapping along waterway margins but increasing survival and productivity for whio using this method is complicated by irruptive predator dynamics caused by occasional masting of beech species (Nothofagaceae).

Stoats are implicated in the severe decline of certain iconic endemic species in New Zealand. Stoats are notoriously difficult to control, as they are highly cryptic and often neophobic around control techniques such as traps and poison baits in tunnels. Stoats are often killed through secondary poisoning in both aerial and hand-lay operations targeting other mammalian pests. We prototype trialled a novel approach to poisoning of stoats: wild-caught ship rats that had consumed (and subsequently died from) a lethal dose of 1080 cereal baits in a captive facility.

We assessed the effect of aerial 1080 control of possums (Trichosurus vulpecula), ship rats (Rattus rattus) and stoats (Mustela erminea) on the survival and nest success of South Island robins (Petroica australis) at Tennyson Inlet, Marlborough Sounds, from 2012–2017. Cereal baits containing 1080 were applied in 2013 when rat and stoat numbers were low, and again in 2014 after a beech mast when rat numbers were high. Survival rates of 134 banded adult South Island (SI) robins and 209 SI robin nests were monitored.

Modern aerial 1080 (sodium monofluoroacetate) operations are effective in reducing population densities of possums, rats and stoats, thereby reducing predation pressure on birds. Debate regarding 1080 use, however, continues to centre on potential non-target effects, with some groups claiming that birds are killed in large numbers such that forests “fall silent”. We investigated these claims by recording birdsong for 5–8 weeks before and after three separate 1080 operations in the Aorangi and Remutaka Ranges of the lower North Island, New Zealand.

Kea (Nestor notabilis) are highly inquisitive parrots endemic to Aotearoa/New Zealand that often interact with novel items in their environment. To help reduce the risk of by-kill of kea during aerial 1080 pest-control operations, we investigated how kea perceive the different types of cereal baits typically used in such pest control.

To help develop new tactics for the local elimination of possums using a fast-acting toxin (1080; sodium fluoroacetate), we tested whether possums that had survived a cereal 1080 baiting could be poisoned with an alternative peanut butter paste (PB paste) bait that differed greatly in appearance, texture, smell, and taste. A two-stage field trial was undertaken in 2018 in three 50−80 ha study blocks in mature pine forest near Rotorua.

New Zealand aims to eradicate possums (Trichosurus vulpecula) and ship rats (Rattus rattus) nationally by 2050. This aim will require more effective tactics for locally eliminating these pests. Therefore, we explored whether possums and rats could be eliminated from large areas using pre-feeding and two applications of sodium fluoroacetate (1080) bait spaced a few months apart.

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.