Baits are known as rodenticides within the industry – they all work on the same principle of trying to get a rodent to consume a lethal dose of a poison by masking that poison within a food material.
Rodents aren’t like dogs – they don’t just hungrily wolf down every bit of food you put in front of them until they are sick.
They are surprisingly fussy about what they eat and will often only eat certain foods which varies from population to population and individual to individual.
They also like to eat a little bit of this and a little bit of that – it’s what we nickname the ‘tapas’ approach.
The problem with this tapas approach is its very difficult to get them to consume a lethal dose of any given rodenticide.
Rodenticides have to have a lot of additives in them such as wax (to stop them rotting) and Bitrex (a bittering agent to ward off accidental human consumption) and typically consist of a mixture of compressed cereals and vegetable fat.
They also generally have very little moisture content and so aren’t really that appetising if rodents have got access to other normal food sources such as refuse and stored foods.
Think of the comparison of a freshly cooked pizza compared to a dry Ryvita crispbread – which one are you going to eat? (The Ryvita is the rodenticide for those unsure).
Chances are you going to continue walking straight past the Ryvita to get at the pizza every time – rodents are just the same.
So if you want rodents to even think about consuming rodenticides, you have to stop them accessing other food sources first (i.e. remove all pizzas).
The vast majority of rodenticides contain anti-coagulants – these cause death through internal bleeding (which is supposedly a humane death).
They kill through chronic action – i.e. they are slow acting.
They are not acute acting – i.e. sudden, like a cyanide pill in a James Bond film.
The advantage of a chronic action is that it overcomes the ‘tapas approach’ mentioned earlier.
The tapas approach means that only small quantities of bait are consumed which in turn means a sub lethal dose of rodenticide is consumed per ‘dining’.
If the action was acute, then the rodent would quickly associate which food source made it ill and simply avoid that for ever more.
The craftiness of a chronic poison is the delayed response means the rodent has already fed 2 or 3 times from the bait before it develops any symptoms and therefore there’s a much greater chance of consuming a lethal dose.
What’s not so clever is rodents have been developing resistance to rodenticides since they were first used in the 1940’s and now it’s pretty rampant.
Certainly anticoagulants such as Warfarin have virtually 100% resistance in both rats and mice.
Very common anticoagulants such as Bromodialone and Difenacoum (these will be the actives in any bait you buy from a hardware store) also have very high resistance levels.
These resistance levels vary from geographic district to district but as an example, Thames Valley area rats have reported resistance levels of 90% to both of these actives.
Brodifacoum and Difethialone still have low levels of resistance but these are very potent rodenticides and therefore have limitations/controls over how and where they are used.
So moral of the story is firstly, just because you put a bait down it doesn’t mean it’s going to eat it and secondly, even if it eats it then it doesn’t mean it’s going to die.
Pest control and pest eradication
Rodenticides, when used correctly, can be effective at pest control.
Pest control is the process of supressing rodent numbers – keeping a rodent population at a certain level.
Pest eradication is the process of reducing a rodent population to zero – i.e. eliminating the problem all together.
Rodenticides, when used correctly, can be effective at pest control – but they are rarely sufficient on their own to achieve pest eradication.
Pest eradication is typically achieved through targeting the environmental factors that are supporting the rodent population – i.e. food, shelter and warmth.
If these 3 factors are changed so the environment is no longer suitable or capable of supporting a rodent population, then no rodent population will exist – simple as that.
Here at Pestology we assume our customers want pest eradication – we assume they don’t want the repeated investment and compromise scenario associated with pest control.
We therefore focus on targeting the environmental factors supporting any given rodent problem – using rodenticides has its occasional role to play but in the majority of situations we find they aren’t needed.
This has a positive effect on the environment too.
The problem with rodenticides is they still remain active even when the rodent is dead.
Because rodents are at the bottom of most food chains, other animals eat them like popcorn and therefore ingest large amounts of rodenticide.
The rodenticide therefore kills them as well.
This is very much a rural phenomenon affecting Barn Owls and Kestrels but dogs and cats in urban scenarios are very much at risk too – it’s called secondary poisoning.
In general, the use of rodenticides should be questioned every time they come up in conversation – it’s actually quite an old-fashioned and limited approach to reducing or removing rodent numbers.