Chew cards are a safe and useful tool to help detect the presence of predators by looking at their unique bite marks. Chew cards are squares of corflute card, with grooves filled with peanut butter (non-toxic lure), and when predators bite down on the card, it captures their bite marks.
Installing a chew card is a great way to work out what predators might be lurking in your backyard and the best location for your backyard trap. You might also spot chew marks on other things, like fruit, berries, or other infrastructure – and this guide can help you to identify which chew belongs to who.
Installing chew cards
Place the cards in areas where you suspect rat activity, eg. near compost or rubbish bins.
Nailing it to a nearby tree or fence (at a height of 50mm-100mm) will help keep it secure.
We suggest leaving it out for a five to seven nights.
Identifying bite marks
Rats
Rats typically remove large parts or all of the baited portions of the card.Mice
Mouse chews are usually between the channels on one surface of the card, with fuzzy twisted edges rather than clean teeth cuts.
Stoat chews
Mustelids and cats leave paired, circular canine punctire marks, top and bottom.
Possum
Possums leave crushed margins that can sometimes look like water damage. They can also leave moustache shaped teeth marks that are 5-7mm wide. Biting and crushing can extend well beyond the baited portions of the card.
Hedgehog
Hedgehogs leave both circular puncture marks and blunt mandible (lower jaw) incisor impressions.
Credit: Manaaki Whenua Landcare Research, and Predator Free Dunedin.