If you leave the doors and windows to your house open, sooner or later, a robber will appear and try to steal your TV. So, you pick up a gun and shoot this robber, but continue to leave your windows and doors open.
Shortly afterwards, another robber appears, and again tries to steal your TV, so you shoot this one too. The question is, is it easier to keep shooting robbers? Or, is it better to simply close and lock the windows and doors, so robbers can’t get in?
It is just this question people should ask themselves when deciding how to get rid of mice. Baiting with poison is the most common method used by pest controllers to try to keep properties mice and rodent-free. But it has some big problems, which are not often explained to clients by people who promote it. Here are six of those problems:
1. Resistance to the bait
Baits contain anti-coagulants that are designed to kill mice through internal bleeding. Common anti-coagulants would be bromodialone, difenacoum and brodifacoum. The problem is, these baits have been around since the 1950s and mice have developed resistance.
Exact levels of resistance are difficult to determine as they vary from population to population. But a recent study using DNA sequencing for the detection of anticoagulant resistant mutations, shows that more than 90% of mice examined carried these mutations, leading to resistance being found at 29 of the 30 sample sites.
2. The need for the mouse to consume a lethal dose
Mice feed from a large number of locations and a large number of food types – they like a little nibble of everything from everywhere. This means they are less likely to consume a sufficient quantity of bait to ingest a lethal amount. A more likely scenario is that they will ingest a small quantity of the bait, and develop symptoms of illness. They will then associate the bait with feeling unwell, and never go near it again.
3. Behavioural resistance
It is a legal requirement in most situations for bait to be contained within bait boxes for safety reasons. Behavioural resistance is where mice have ‘learnt’ to associate bait with bait boxes, and therefore refuse to enter them. They, simply, climb over the top of them, or run around them. The same phenomenon occurs with glue boards and snap traps.
4. Dead bodies
Where mice are affected by baits, they will generally die within your property somewhere. This can lead to quite a stink where the body putrefies, as well as generating a blowfly or maggot nuisance. Or both.
5. Non-target species
Anti-coagulant baits will kill all mammals in just the same way they kill mice. After all, these products are poisons and designed to kill. Most baits are brightly coloured. They have attractive smells to entice rodents to eat them. Some even smell of chocolate! So there is a significant risk of consumption by other animals such as dogs, cats and birds, and even children. Also, a dead mouse killed by poisoning will still contain the anti-coagulant. So, an animal that eats the dead mouse will also ingest the poison, and will be affected by the anti-coagulant. This is called secondary poisoning. It is recognised as a big problem for birds of prey and other larger animals above the mouse in the food chain.
6. It’s a short term solution
Baiting is a method of mice control (i.e. keeping on top of the numbers) rather than a method of elimination (i.e. completely removing all mice).
It is very unlikely, for all the reasons outlined above, that baiting will ever remove 100% of the mice within a given building. There will always be a population that remains, to re-establish larger numbers once more.
Proofing is a method of elimination – it removes all mice through habitat manipulation, that is, blocking off their access to food, shelter and warmth. Pests require a habitat and cannot exist without one. Therefore, they cannot generate resistance to proofing.