What does it look like?
Weasels are the smallest and least common of the three mustelids in New Zealand. They have a thin, muscular body and a small head. Their colouring is very similar to stoats, but with a more red-brown coat and a shorter tail uniform in colour. Weasels are usually found where there are plenty of mice, in gardens, long rank grass or near trees and buildings, rather than in open paddocks.
They grow to 20-25cm long and will attack prey that is much larger than themselves, usually eat the flesh from the neck and head area of their prey.
The easiest way to determine whether mustelids are present in an area are their scats which are long and thin, they often also have a characteristic tapering twist at each end. They are filled with fur, feathers and bone fragments. They are hard and black when dry. Scats are often found out in the open, like in the middle of a track. Mustelids secrete scent onto their scats, a thick, oily yellow powerful smelling fluid called musk. This acts as a sign to other mustelids in the area.
Why is it a problem?
Mustelids can be devastating to native bird life and other fauna. They have very good hearing and a strong sense of smell. They are not as common in New Zealand as other mustelids, but they also have an impact on native birds and lizards, especially skinks. Weasels produce one to two litters each year, each containing four to six young. The young in the litter grow very fast and are weaned at four weeks, at which time their eyes open. They can hunt and kill from five to eight weeks old.
Control methods
Traps
The Department of Conservation (DOC) series of traps, the DOC 150, 200 and 250, are used nationally for predator control. The DOC 150 and 200 are suitable for catching stoats and weasels, while the larger DOC 250 can kill any mustelids. These traps are easy to use but you need to be strong to set them. Always follow trap manufacturer instructions when using traps and consider using a setting tool for safety.
Good places for traps are areas where weasels would be travelling or hunting for rabbits and other prey (near cover, along streams, offal holes, pathways, tracks and fence lines, tree lanes and forest margins). If you don’t catch them after some time, then experiment with different bait and/or locations. You can modify the trap with a plate ramp and/or duct tape on the metal plate (metal is a non-natural (cold) surface and is believed to create aversion behaviour in some individuals).
If you are trapping over a large area, then set the traps about 100-200m apart. Put a number on each trap and keep a record of how many have been set, when, and where.
Bait and check the traps at least once a month and change the bait. Remove and dispose of old bait away from the trap. Check traps more often in late summer and autumn as bait deteriorates faster, food sources dwindle and catch rates can go up. Wear gloves when handling the bait and setting traps as mustelids can detect and be put off by human scent.
All DOC series traps are also capable of killing rats and hedgehogs. If you have cats, then use eggs as bait and avoid meat or buy a Weka link extension for the trap which also works to keep cats out. For more information on how to use DOC traps, visit https://predatorfreenz.org/ , www.doc.govt.nz, search “backyard trapping” or contact the Regional Council for solutions to issues encountered.
Bait/Lure
The best lure for mustelids is fresh or salted rabbit. Eggs or fish flavoured cat food work well. There are commercial long-life baits on the market. Raw fat is very attractive over winter. Spray on lures are also effective. A piece of bait or fish can be dragged around on a piece of string to make a scent trail leading to the trap.
Shot rabbits make good mustelid bait and can be frozen until you have enough to salt. Partially defrost rabbits (there is less mess when butchering). Put the salted bait on top of two or three nails inside your traps to help it last and to aid scent dispersal. The bait should last around three weeks depending on the weather and the shade on your trap site.
Dispose of all used bait carefully, either bury or remove from the area. You must not leave used bait in the field where stoats may find it, taste it and be put off going into traps.
Use scent and by-kill to your advantage. Utilise a freshly killed weasel by rubbing its anus over the trap. This will create a smell “neon sign” irresistible for other weasels, increasing curiosity and likelihood of successive kills. Using sex-drive can also solve the issue of abundant food sources in the environment reducing the attraction of carrion as bait. Additionally, using weasel scent or freshly killed rats/mice will lure these and other predators which are looking for these animals as prey.
More information
See also:
Related links
- Weasels – DOC (Department of Conservation NZ)
- Predator Free 2050 Trapping Guide (PDF)
- Where to Buy Traps and Equipment – Predator Free NZ
- Hawke’s Bay Regional Pest Management Plan 2018–2038 (PDF)
- Fine-Tuning Your Predator Control – Webinar
- How Do I Identify My Pest – BioNet
- DOC 200 Predator Trap Specification (PDF)
Management Programme
Site-led Pest Programme
Pests listed under the site-led programmes, and most of the other pests included in the RPMP, are capable of damaging habitats and important ecosystem processes, or competing with indigenous species for food, or prey directly on native species. Pest management, habitat protection (e.g. via fencing) and habitat restoration/creation (e.g. via planting) are key management measures in halting biodiversity decline in Hawkes Bay. A site-led management programme significantly assists with the delivery of each of these goals.
More informationSustained Control Programme
Sustained Control exists to hold well-established pests at an acceptable maximum. However, the costs of management and control grow in-step with the size of the invasive population. Because cost:benefit returns can fall to 1:5 or less, most of this work is focused on specific sites of high ecological value. While the spread of these pests between neighbouring properties remains the predominant risk, in some cases control within properties is still sought and warranted. A sustained control programme will hold populations to maximum acceptable limits over the period of the RPMP.
More informationRules
Plan Rule 16
All occupiers within a Predator Control Area shall maintain ferrets, stoats, weasels, and feral cats in accordance with the Hawke's Bay Regional Predator Control Technical Protocol (PN 4970)
More informationSections 52 and 53 of the Biosecurity Act (1993)
No person shall knowingly communicate, cause to be communicated, release, or cause to be released, or otherwise spread any pest or unwanted organism, in accordance with Sections 52 and 53 of the Biosecurity Act 1993
More informationTaxonomies
FamilyMustelidae
TypeAnimals
GroupMammal
HabitatLand
Management ProgrammeSite-led Pest ProgrammeSustained Control Programme
RulesPlan Rule 16Sections 52 and 53 of the Biosecurity Act (1993)
