Note: The article below is intended as an overview. For the full version, read our Starter’s Guide to Predator Control on Farms [PDF 894 KB]
Introduced predators (rats, mice, possums, stoats, ferrets and weasels) create havoc on farms. They eat crops, spread disease including bovine TB and Leptospirosis, damage equipment, and harm native plants and wildlife. They also breed fast: one pregnant rat can result in 400 more rats in just six months.
The good news is that predator control can make a significant difference on your land, but knowing when and how is the secret to being successful and keeping costs down.
Your toolkit
Your predator control toolkit may include one or more of the following:
Toxins – Effective over large areas with dense predator populations while saving time, money and resources. However, you must carefully consider any potential effects of toxins on your farm. Desirable wildlife and livestock must not have access to baits.
Trapping – Useful for ongoing control once predator numbers are knocked down by toxins and/or night shooting, but a slower and potentially less effective method.
Shooting – Can be a useful method for possums, especially at night during spring when possums are abundant. Not effective for rodents or mustelids.
Note: All tools have their advantages, limitations and consequences. Overuse of the same tool will reduce its effectiveness. Tool selection depends on habitat, scale, which predators are present and how much time and money you put into it. For the best chance of success, you’ll also need to team up with your neighbours.
Wetlands and riparian zones
Wetlands and waterways are a critical part of any farm. However, rodents, possums and mustelids all favour the protection provided by these areas and their impact on wildlife can be devastating. Wetland and riparian margin pest control needs to target all three types of predator.
Possum control – One option is to night-shoot wetland willows when bud-break occurs in spring, then follow up with kill traps. Another option, if no pigs are present, is to use bait stations 30cm off the ground at 150m spacings on trees, well away from stock access along the inside of fence-lines.
Rodent control – If trapping, Goodnature A24 automatic resetting traps are ideal. Another, cheaper option is rodent snap-traps. During times of higher rodent populations, bait stations may be more effective.
Mustelid control – Use DOC 200 wooden box traps with enlarged openings (4×4 mesh squares) to target weasels, stoats and ferrets.
Bush blocks
Bush remnants on farms are often highly valued by farming families — as shown by the number of bush blocks that are fenced off and, increasingly, protected by covenants. However, predator species also pose a huge risk to these areas. Without predator control, these habitats and the native wildlife that depends on them will continue to decline, even with stock exclusion. Rodents, possums and mustelids all favour the protection provided by these areas, so predator control will need to target all three groups.
Possum control – Seasonally night-shoot bush-pasture margins and trees favoured by possums as flowers, buds or fruit come on e.g. pine, willow, larch, and natives (mahoe, cabbage trees, kōwhai). Follow up with kill traps. Service and re-bait about every 2-4 weeks. Alternatively, if there are no pigs present or livestock access, use bait stations 30cm off the ground on a 100-150m grid. Ensure dogs and livestock can’t access any bait.
Rodent control – Goodnature A24 automatically resetting traps are ideal for rodents. Place on a 75–100m grid, about 100–200mm off the ground on trees. Lure with peanut butter and check every 2-4 weeks. For high populations, bait stations may be more effective.
Mustelid control – Use DOC 200 wooden box traps with enlarged openings (4×4 mess squares) to target weasels, stoats and ferrets.
Buildings and storage areas
Buildings, sheds and food storage areas form a valuable part of most farming operations. However, they can also attract large numbers of rodents, so ongoing effort is required with a range of tools to reduce trap or bait shyness.
Goodnature A24 automatic resetting traps are ideal for rodents. Place 10–20cm off the ground, near food sources or on trees near pump sheds. Lure with peanut butter and check every 1-4 weeks.
For large populations, bait stations may be more effective. Work on installing one bait station per shed bay/pump shed or one station per 20m2 for rats. Pulse Ditrac, Contrac or Pestoff blocks every 4–6 weeks. Ensure stock cannot access bait.
Cost
Cost can vary from place to place depending on the scale, terrain, habitat type, ease and type of access, the type of tools being used, pest density and whether labour is voluntary or factored into pest control inputs.
As a rule of thumb, a least two devices per ha will be required for combined rat, possum and stoat suppression. Preferably these should include one trap and one bait station. Rodent control in sheds and buildings is more device-intense and should be costed separately.
For more information on predator control specific to your area, we recommend that you contact a predator control specialist or your regional council.
For more detailed advice, see our Starter’s Guide to Predator Control on Farms [PDF 894 KB]