Testing the effectiveness of integrated pest control at protecting whio (Hymenolaimus malacorhynchos) from stoat (Mustela erminea) predation in beech forest (Nothofagaceae)

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).

Toxin-laced rat carcass baits for stoat elimination

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.

The effects of beech masts and 1080 pest control on South Island robins (Petroica australis)

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.

Bioacoustic monitoring of lower North Island bird communities before and after aerial application of 1080

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.

Assessing kea perception of cereal baits using modelling of spectral reflectance

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.

Dual 1080 bait switching for killing cereal-bait-shy possums

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.

Attempting local elimination of possums (and rats) using dual aerial 1080 baiting

New Zealand aims to eradicate possums (Trichosurus vulpecula) and ship rats (Rattus rattusnationally 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.

Dead birds found after aerial poisoning operations targeting small mammal pests in New Zealand 2003–14

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.

Spatiotemporal changes in relative rat (Rattus rattus) abundance following large-scale pest control

We examined spatiotemporal changes in rat tracking indices following large-scale (>10 000 ha) pest control using aerial applications of sodium monofluoroacetate (1080) baits in Tararua Forest Park, North Island, New Zealand. Population control of rats appeared effective, with few to no rat tracks recorded in treatment areas during the 6 months after control. However, the rat tracking index increased rapidly after that, and 24–30 months after control, rat tracking indices in treated areas exceeded those in the non-treated areas.

Contamination of forest ecosystems by sodium fluoroacetate (Compound 1080).

Predictive and conceptual models are used to examine the contamination, toxicology, and residues of sodium fluoroacetate (Compound 1080) in relation to its application in vertebrate pest control programmes on forest and pastoral lands.
As a pesticide, the toxin appears to be neither mobile nor persistent. Exceedingly slender opportunities exist therefore for significant contamination of susceptible components of the environment.