More than one way to kill a rat
More than one way to kill a rat
There's more than one way to kill a rat, a possum or a stoat. A wide range of techniques and tools are used to control pests, depending on the threats and the terrain you are dealing with.
Ground control-using traps, bait stations or culling-is the most widely used method, and can prove highly effective where the terrain is suitable and regular checks can be made. Modern traps are humane, effective and designed to avoid harming native birds. The Department of Conservation (DOC) maintains a network of over 180 000 traps and spends more than $5 million per annum on stoat and rat trapping.
Bait station
As part of the trapping programme, DOC also supports possum fur recovery in a number of regions, which can help supplement mainstream possum control initiatives. But even with high fur prices, consistently high numbers of possums are needed to make trapping economical. Furthermore, to ensure the protection of native species, possum numbers must be driven down to very low levels- less than five possums recovered from 100 traps-which is uneconomical for a fur recovery industry.
Poison bait stations employ toxins such as 1080 gel, brodifacoum (also known as Talon®), diphacinone, cholecalciferol (Vitamin D) and potassium cyanide (Feratox). The choice of toxin depends on the specific pest target, the surrounding environment, and potential risk to native wildlife and human health.
Ground control methods are precise, but still pose some risk to non-target species such as native wildlife, dogs or farm stock. They are also labour-intensive and expensive. Despite this, with more than 400 000 hectares under management, ground control is DOC's most widely used pest control approach.
Some areas requiring predator control are too remote or too difficult to effectively negotiate on foot, leading to reduced predator kill rates. In other areas, predator plagues simply overwhelm trap and bait stations, leaving critical populations at risk. In these circumstances, DOC may apply 1080 baits from the air. This biodegradable toxin is the only effective poison that has been registered for on-going aerial pest control campaigns in mainland New Zealand.
The financial costs of aerial treatment are significantly less than ground control-in some cases less than a quarter. Nevertheless, DOC applies aerial 1080 over less than 2 percent (about 150 000 hectares) of the 8.6 million hectares of public conservation land. For every hectare of aerial treatment, more than 2 hectares are covered by ground control operations.
DOC has fine-tuned and improved aerial application techniques over many years. Global Positioning Satellite (GPS) technology is now used to ensure baits are accurately and consistently targeted. The amount of bait applied has also been greatly reduced. In the early 1990s, up to 18 kg of bait per hectare was used. Today, sowing rates of 2-3 kg per hectare are now common, thanks to advances in application techniques to improve effectiveness and minimise risks to native species. Deer repellant can also be used to protect valued recreational species.
One individual 1080 bait is a maximum of 0.15 percent toxin; the rest is simply a carrot or cereal base. This means that, at today's sowing rates of 2-3 kg of bait per hectare, a treated hectare is covered with less than 1 teaspoon of actual toxin.
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