The first modern rat and mouse poisons were given the name - First Generation Anti-coagulant Rodenticides or FGAR’s for short, and these were developed back in the 1950’s as an answer to the every present problem of commensal rodents – this is the term for those species that live completely off mankind. FGAR’s were designed with lower rates of toxicity than the second generation one’s and required the need for rodents to feed multiple times before they had absorbed enough of the active ingredient; this meant that many rats and mice survived eating it. 

As the overall rodent population declined leaving only those that could consume the bait and live, their offspring were born with a built in immunity to these chemicals; we know that rats and mice breed a lot and so within a short space of time most of the rodents were born with full blown immunity: they could ingest the poison and metabolise it so that it no effect on their health. 

‘Modern’ rodenticides weren’t working so scientists went back to the drawing board and developed the Second Generation of Anti-coagulant Rodenticides which they gave the catchy name of SGAR’s to, these chemicals were designed to be more toxic and for the chemicals to work after just a single feed. We had the ultimate weapon for use against these rodents – or so we thought, in fact rodenticide is the most commonly found chemical worldwide. 

The idea behind SGAR’s is that the chemical binds within the animals liver following ingestion and then over a course of a few days it causes changes that prevent the blood from clotting, as the blood starts to thin it is pushed out of the animals circulatory system and starts to accumulate within voids such as those found in joints and around the lungs. The animal slowly dies from internal bleeding, this all sounds rather grim but there is evidence that shows it is relatively painless and as a way of controlling rats en-masse ie in huge numbers, its more humane than trapping or dispatching with dogs and air rifles. 

So science saves the day and we have this super poison which we can rely on to stop rodents in their tracks, unfortunately as with many great things, our stupidity gets in the way. Rodenticide used to be used everywhere and to be honest it is still heavily relied on as the first course of action when a rat is seen. We started this blog with the statement that a good old bit off poison will do the job and the inconvenient truth is – it won’t, well, not always. 

You see that one of the most commonest SGAR’s used the active ingredient bromadiolone, just type in bromadiolone into Google and up comes adverts for Rat and Mouse Killer; some even call it Super Rat and Mouse Killer (I didn’t know that there was a Super Mouse and now I have an image of a mouse in a little red cape). 

They sell these poisons in 10 kilogram sacks, typically for use on farms where it will be poured out onto barn floors or throw under haystacks in the worst scenarios that is, and once again some rats survived eating the poison and so the spread of resistant genes starts.  

So what is the answer if the SGAR’s are not going to work? 

The number one solution will always be to trap, trapping can be difficult and time consuming so many large companies will not use traps but rely on the chemical approach as a sole means of control. And that brings us to the key to resolve any rodent infestation = achieving control by discovering the access point and then sealing it shut. This is something that you can do if you have the time with traps by tracking the animals routes and determining the entrance point. Once that is uncovered its relatively easy to finish off what’s running about and leave the customer permanently rodent free. 

The scientists will keep on bringing new chemicals out due to demand and that’s fair enough; we use rodenticide and I’m personally not against it, just the lazy practise of throwing poison in someone’s loft and saying that’s it job done, and then coming back in nine months to do it all again at the customers expense.