mustelids Pest Animal Factsheet Introduction

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1 mustelids Introduction The introduction of mustelids is regarded as one of the worst mistakes ever made by European colonists in New Zealand. They were introduced to reduce the rabbit population, but have since become a major predator of native species. Mustelid predation has led to the extinction of some native birds and has aided the decline of the kiwi, kakapo, takahe and many more. Damage to native birdlife on farms often goes unnoticed by landowners, due the very secretive nature of ferrets, stoats and weasels. Ferrets, stoats and weasels can travel very long distances and live in home ranges which vary in size up to 200 ha. Males tend to occupy larger areas than females. Mustelids are shortlived but very productive breeders. Most young are born during spring or early summer and litter size is dependent on the abundance of food. yellow undercoat, with long guard hairs that are black at the tip, giving a generally dark appearance. The leg and tail appear darker than the body. The lighter facial region has a dark mask around the eyes and across the nose. Their smell and hearing are the main senses; their eyesight is poor by day, but better at night. Ferrets are relatively poor swimmers and climbers in comparison to stoats and weasels. Ferrets prefer more open country and are seldom found deep in the forest, although they will use forest edges. Ferrets are often common in areas containing high rabbit numbers. They are nocturnal, so they are not often seen in the wild. Stoat Mustela erminea Ferret Mustela furo Stoats have long thin bodies, smooth, pointed heads, short round ears, and round black eyes. They are smaller than ferrets. Males are up to 300 mm long and weigh around 350g. Male ferrets grow to 440 mm and females to 370 mm in length. They have a creamy Females are up to 250 mm long and weigh around 240g. Their fur is brown with creamy white underparts. They have a distinctive bushy black tipped tail.

2 There are few places they cannot reach. They are strong swimmers in both fresh and salt water, and islands within 2 km of the mainland are vulnerable to stoat invasion. Stoats are agile climbers and can live almost everywhere. Weasel Mustela nivalis vulgaris Mustelids are also a major threat to poultry, killing hens and taking eggs. They will also target pets such as guinea pigs and pet rabbits. Ferrets are significant carriers of Bovine Tb and toxoplasmosis. Pest Animal Status Mustelids are Suppression animals on mainland Southland. Mustelids are Exclusion animals on Stewart Island, offshore islands and inland islands. Weasels are the smallest and least common mustelid in New Zealand and are about 200 mm long. Males weigh up to 150 g and females up to 80 g. Their fur is brown with white underparts often broken by brown spots. Their tail is short, brown and tapering and lacks the black tip. Weasels prefer disturbed areas like suburban gardens, farmland, scrub and cutover or exotic forest, and forest edges. What is the problem? Mustelids are extremely devastating predators that pose a threat to the long term survival of many of New Zealand s native species. Mustelids will kill almost anything from native bats to freshwater fish. Mustelids are major predators of virtually all native birds including endangered; kiwi, kaka, yellowhead, blue duck, yelloweyed penguin, native pigeon, and saddleback. Note: Regulation 3, Wildlife (Farming of Unprotected Wildlife) Regulations 1985, prohibits the keeping in captivity, conveying to, or liberation of any unprotected wildlife (Ferrets, Polecats, Stoats, Weasels) on Stewart Island and any other island within the territorial sea of New Zealand, except the North and South Islands. Regulation 25. The regulations also prohibit, without a licence, the keeping of more than three specimens of unprotected wildlife: Regulations 2 and 4. Ferrets have been designated as unwanted organisms under the Biosecurity Act Strategy Rules Except as authorised by or under the Wildlife (Farming of Unprotected Wildlife) Regulations 1985, no person shall have in his or her care any sexually mature Mustelid which has not been neutered. Any person keeping a Mustelid shall keep the Mustelid in a securely fastened cage from which the Mustelid is unable to escape at all times. No person shall possess, transport to, or release any Mustelid on Stewart Island, any offshore island or any inland island. Control Currently, the most effective control method for mustelids is trapping.

3 Trapping Environment Southland loans traps for the control of mustelids. To purchase traps contact Environment Southland for supplier details. To be effective, trapping must be ongoing due to the rapid reinvasion of mustelids into controlled areas. Suitable traps for mustelids include: Stoats and Weasels DOC 150, 200 or 250 traps (see predator traps com for details) Mark 4 or 6 Fenn traps KBL tunnel trap Victor (modified rat trap) Live capture tunnels Ferrets DOC 200 or 250 traps (see predator traps for details) Mark 6 Fenn trap Timms ferret trap KBL tunnel trap Live capture tunnels Leg hold traps can be used to catch mustelids but should be used in a tunnel and must be checked daily. Trap Tunnels Traps for mustelids should be set in a tunnel or under a cover to protect non target animals. Mustelids also investigate tunnels and burrows encountered while hunting, so using a tunnel will increase your catch rate. Plans for a Fenn Mk 4 trap tunnel are shown below, if Mk 6 Fenn traps are used the box will need to be widened from 200mm to 250mm to accommodate them. Commercial trap covers/tunnels are also available. Makeshift tunnels can be constructed from any material handy such as timber, bricks, tiles or logs. Trap Placement Traps set beside linear landscape features, such as fencelines, waterways, forest edges and roads, around farm buildings and offal pits and in areas with abundant prey produce the highest catch rates. When controlling large areas, one trap should be placed in every 1020 ha to ensure that at least one trap is within each mustelids home range. Figure 1 Plan of the wooden floored trap tunnel developed for Fenn traps

4 Bait The most effective mustelid baits are fresh meat (rabbit is particularly good) and hen eggs. Meat baits go off relatively quickly and loose their attractiveness. As a result, they need to be replaced every few days. of the hood is facing downwards and about 1520 cm above the ground. Place the bait on the safety pin and then set the trap as you would a normal mouse or rat trap. Directions Salted rabbit is an effective bait for Stoat and Ferret traps and has a much longer field life than fresh rabbit. Homemade salted rabbit meat bait 1. Skinned and gutted rabbits can be frozen whole until you have enough to salt (a dozen rabbits makes a bucketful). 2. Chop rabbit into bait sized pieces with a cleaver about 25 pieces per reasonable sized rabbit. 3. Layer the pieces in a bucket with a handful, or two, of noniodised salt per rabbit. Mix, cover and leave in a cool place for 24 hours. 4. Mix again, and then drain off the liquid. 5. Bag the pieces in plastic bags and freeze. The pieces of bait should freeze free flow and be ready to use as you need them. Excess bait left after a days trapping can be refrozen. 6. Put the bait on a peg above the ground in 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. Modified Victor Trap Plan The modification described below converts a Victor rat trap into a cheap, but relatively effective, stoat trap. This trap design will be effective only on stoats, weasels and rats. Trap location The trap is best attached to a fencepost or tree by drilling a hole in the two back corners of the wooden trap base and screwing it into place. The trap should be positioned so that the front opening Figure 2 Completed trap Glue a safetypin to the metal trigger plate of the trap with the point opening towards the front. This allows a meat bait to be attached easily. Using the hood pattern, overlaid, cut out a plastic hood from the side of a two litre plastic milk bottle, remembering to take the small section out of the middle to allow the arm of the trigger mechanism to reach the trigger plate. Thin plastic other than milk bottles could be used. Attach the hood to the trap by sliding the back of the hood under the spring mechanism, and then staple the tabs at the front of the hood to each side of the wooden base of the trap. When in place, the hood

5 should allow the spring loaded arm of the trap to pass freely just in front of it. The opening in the back of the hood should also allow the trigger mechanism to function freely. Bait Meat bait such as rabbit, possum or fish is suitable for use in this type of trap. Advice & Information To find out more information contact: Biosecurity Officer Environment Southland Private Bag 90116, Invercargill Phone Toll free Fax Website