Rat trapping trial

We have run a highly successful rat control community-based programme for the last ten years. This programme uses a bait block containing bromadiolone as an active ingredient. The design of these blocks was to have a very low, to no, secondary kill. In other words, if something ate a dead or dying poisoned rat it would not also be poisoned. We felt this was important because of domestic cats and dogs in the area. When you have a programme like this it is important that you have the majority of people in the area on your side and we would not get that if we were knocking off their cats and dogs. Incidentally, some baits, brodifacoum for example, are designed to have a secondary kill. This bait, which goes under a number of proprietary names, is freely available at most hardware stores.

Successive programmes around the country which have tried to get a good knock down of rat numbers using only traps, have never been successful. Remember it is not how many rats you catch, but the number of rats left. Rats are prolific breeders with one pair in spring potentially responsible for up to 2000 offspring by late autumn. Therefore, our aim has been to eradicate all resident / breeding rats and then knock out reinvasion to prevent the rats getting re-established. To date we believe we have been successful.  

So why look at traps? The use of toxins has never been ideal.

There are two motivations for this trial. One is that ruru / morepork owls nest in the gully. They catch mice. Mice also feed on the poison baits. Although the bait should have a low secondary kill, we do not know what effect it would have on chicks. Secondly Hamilton City Council has always been uncomfortable with our community-based programme.

Owl with mouse at nest in Mangaiti Gully