How to Detect and Trap Predators


Placing and baiting traps

Read our Trappers Guide to Predator Free Port Hills for detailed information on the traps sold by the Summit Road Society.

Finding the best location for your trap(s) will depend on the type of trap you have and the predators you want to target. When placing traps, if children might come onto your property, make sure that they cannot reach the trigger mechanism, either by placing the trap out of reach e.g. mounted high enough on a tree, or by making sure it is inside a secure trap box which is designed so that children cannot reach inside.

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To identify the best place to put traps, a good way to start is to place some chew cards around your property. These are cards impregnated with a lure which encourage pests to chew on them. The bite marks left behind can then be used to identify the pest animal. That way you can see which pests are a problem and where they are the most prevalent. Your local co-ordinator should be able to supply you with some chew cards and can give you some advice on how to use them.

Chew cards showing typical chew marks, from left to right: possum gnaw marks, stoat/hedgehog/cat puncture marks, rats chew entire sections of card, mice chew small sections of card (Halo)

 

Where to place your trap

To place traps, some tips to keep in mind are:

  • Consider where pests might be in your backyard and why. Many predators can be found near water and food sources such as fruit/nut trees, roses, compost bins, and chicken houses. Rats and mice often enjoy the warmth of your house during the colder months.
  • Predators will often use regular pathways in the grass, along fence lines and ridges, down the side of the house, near compost bins, waterways and culverts – basically, the easiest path to travel along.
  • Look for ‘sign’, such as faecal pellets, bite marks, scratch marks, bark with urine stain, and partially eaten leaves.
  • Possums and other mammals like to be warm and dry. Rather than get their feet wet walking through long wet grass, they will use tracks and roads to move around, unless there is a food source that draws them away from these main thoroughfares. They tend to be more active on clear moonlight nights and stay closer to home when the weather is bad. This also means that they tend to nest in sheltered spots including thick vegetation, such as in riparian plantings, and in trees covered in vines.
  • Mustelids will be attracted to locations where mice, rats and chickens are present, as well as rabbits.

 

Place traps on a flat surface and make sure that the entrance and exit are clear of obstructions including long grass, other vegetation or sticks etc. For Trapinator possum traps, please mount them onto a tree at least 1m off the ground.

Choosing the right baits and pre-feeding, especially for mustelids and rats, are also important. Place the lure in the box and around the entrance without setting the trap for a week or two, so the rats get used to entering the box. This helps establish your trap as a source of food and creates scent trails that other rats will follow. Then set the trap and catch them.

 

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Stoat that has been trapped
(Avenue, Wikimedia Commons)​

 

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There are lots of options for baits/lures. These include several commercial lures that you can buy, or using your own.
Commercial lures are normally easy to handle and designed to last longer than fresh bait. Some examples of lures for each pest include:

●      Mustelids: fresh baits are preferred and include hen eggs or fresh meat e.g. rabbit, beef, chicken, possum, fish-based cat food, dead mice or rats, or you might want to try salted or freeze-dried meat. Eggs can also be hard boiled.

●      Possums: a flour and icing sugar mix of five parts flour to one of icing sugar with the option of adding a spice such as cinnamon; or try pieces of fruit. If using the flour-icing sugar mix, put it in a soft drink bottle with holes drilled into the lid and spray the lure on the trap and around the trap in order to lure the possum in to the trap. For raised traps, always place lure below traps to encourage animals to move up to the trap. The white colour of the flour-sugar mix also acts as a visual lure. Reflectors can also be used to attract possums to the trap.

●      Rats and mice: peanut butter or nutella

Also, some pests have a clear season of trap-ability. For example, ferrets, especially females, are relatively easy to catch in summer and autumn but more difficult to catch in late winter and spring.
 

To maintain your traps you will need to:

●      Check and rebait traps at least once a month, and ideally more frequently if using fresh bait as it needs to be palatable for the pest to interact with the trap enough to be caught in it e.g every four to five days for fresh meat, and every two to three weeks for eggs.

●      The more pests there are in your area the more frequently you should check your traps.

●      Make sure the trap is still working - to test a trap use a stick to trigger it.

●      Some traps will need a bit of maintenance to keep them working. It’s a good idea to lubricate the working parts of the trap once or twice a year.

The Predator Free NZ Trust website has trapping guides targeting each pest species.

Recording Your Traps and Catches

An important aspect of achieving a Predator Free Port Hills is to coordinate our trapping efforts. We can do this by recording trap locations and  the number and type of pests being caught.

Recording catches also means that we can see how much progress has been made, which helps with publicity and funding, but also keeps everyone informed and enthusiastic as we can see the collective results of the group.

Help us achieve our goal of 4000 households trapping on the Port Hills through signing up your household, mapping your traps and logging your catches.
 

Pest Detection

Pest detection helps identify the types of pests that are present and to get a measure of pest activity. It can be done using tracking tunnels or you can simply look for animal scats i.e. poo, or toothmarks on fruit and nuts. Tracking tunnels will give a measure of changes in relative abundance over time.


A tracking tunnel is a run-through tunnel containing a pad that shows the footprints of animals that travel through the tunnel. A tracking pad can be made by placing two pieces of paper either side of a sponge soaked with a tracking medium like food colouring. As an animal passes through the tunnel it picks up the tracking medium on its feet, then, as it departs from the tunnel, it leaves a set of footprints on the papers. It is a non-destructive sampling technique so it does not impact the target species or, any non-target species.

Footprints left on the tracking papers can then be compared to pictures of tracks from different types of pests (see below).

These images show examples of tracking tunnels - a homemade tracking tunnel, top (DOC) and a commercial tracking tunnel, bottom (Science Learning Hub).

Check out this video for instructions on how to make your own tracking tunnel with materials from around the house. A great activity for the kids.
 

 

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Examples of pest footprints (Pest Detective)

 

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Possum scats top, and stoat scat middle left (Jaqui-nz, Nature Watch),
mouse and rat droppings middle right (Goddamn Bowtie, doctorwhogeneral.wikia.com);
possum damage to trees (DOC, Steele, Pest Detective)

One thing to consider is that some predators will peak in numbers and/or activity at certain times of the year. For example, stoat numbers peak in summer, but that peak is only for a very brief time and this is when many species of native birds appear to be most vulnerable.

Another thing to look for are animal scats. For example, stoat scats are black, long and thin, and usually are full of bones, feathers or fur, and 40-80mm long. Scats are often deposited as a 'marker' in prominent positions such as on top of logs or stones along travelling routes. The scats of ferrets and weasels are very similar, only differing in relative size. However, take care not to confuse these scats with blackish bird droppings - the contents of the droppings should identify the owner.

 

Possums also cause distinctive damage to vegetation. The Pest Detective is a great website for identifying pests if you are not sure.

Pest monitoring is a more systematic process that helps assess the prevalence of pests and predators over time. As it uses a systematic method, results can be compared over time and between locations.  It involves the placing of tracking tunnels and chew cards at set points on a monitoring line. Tracking cards are usually placed out for one night, chew cards for 7 nights.

Predator Free Port Hills is currently undertaking monitoring in reserves in selected suburbs across the Port Hills.

To get in touch, please email Predator Free Port Hills or sign up via our website.

 

 

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