Rats, rodenticides and resistance: what next?

Complacency is not an option when dealing with rodent infestations but there are plenty of ways to limit unwelcome visitors on a shoot

- MIKE SWAN

I have suspected it for a while, but confirmation popped into the inbox the other day. Four rat-tail tips that I had sent to the Animal and Plant Health Agency (APHA) for genetic screening came back positive for second-generation anticoagulant resistance.

From here on in, the two most used rat poisons, bromadiolone and difenacoum, will be as good as useless on my shoot. If we were daft enough to use them, we would simply be risking sending the chemicals up the food chain to the likes of our barn owls, kestrels and red kites, while having no significant impact on rats.

So where do we go from here? Clearly, rat control is essential on any shoot, so giving up is not an option. This applies especially on a small wild bird shoot like mine, where I have the added risk of rats killing nesting hens and taking eggs. With all this in mind, I have always striven to minimise anticoagulant use and keep rat numbers to a minimum, using all the other means at my disposal, but more of that later.CAL

As far as poison baits are concerned, there is still an anticoagulant option, if with a rather restricted application, and there is a new active substance on the horizon, too. Until comparatively recently, the anticoagulants brodifacoum, flocoumafen and difethialone have been available for indoor use only.

While they are not allowed for the sort of ‘open area’ application around gamebird feeding stations that is the main gamekeeping use, the rules were changed a few years ago so that, depending on the product label, they can be used outdoors around buildings to help control infestations in the buildings themselves.