Reduce Anticoagulant Use – While We Still Can by Richard Strand

The introduction of anticoagulant rodenticides some 60 years ago made rodent control easy. We no longer needed meticulous pre-baiting because the new products were sufficiently slow acting that rats and mice did not associate being poisoned with eating the bait. There was also an antidote to anticoagulants, so if a child or a pet ate the bait, there was time to administer that antidote.

It is hardly surprising, therefore, that anticoagulants revolutionised rodent control to the extent that in chemical terms, there are now precious few alternatives. Yet now we find a raft of new limitations on how these wonder products can be used.

The purpose of this article is to ‘colour in’ why the recent clamp down on anticoagulant use has taken place and the reasons behind some of the restrictions that have been introduced.


The introduction of anticoagulants in the mid-twentieth century revolutionised rodent control


This may be contentious but there is a view that the widespread availability and use of anticoagulants ‘de-skilled’ rodent control. Anybody could, and did, lay some baits, then went away and anticipated a result! Little thought may have been given to where much of this bait was going. Even less thought to where its victims ended up.

From a practical point of view, perhaps one drawback of the first generation anticoagulants was that a ‘kill’ could only be guaranteed by ensuring that the target rodents took multiple feeds to build up that important lethal dose. By the 1970s and the introduction of the second generation anticoagulants (SGARs), one dose was likely to be lethal. This prompted a boom in permanent baiting. Baits could be left in place without the need for regular inspection and they were going to protect your property from invasion by anything that came along and ate them. The only issue was to make sure that these bait stations were always fully charged. If any thought was given to protecting the bait, that concern was to shelter it from the elements rather than from non-target animals. Little consideration was given to what happened to the victims of the bait. How could it when the next inspection was in six weeks’ time?


By the 1970s and the introduction of the second generation anticoagulants (SGARs), one dose was likely to be lethal.​


With the benefit of hindsight, it is not surprising that ‘things went wrong’. In many respects it is a similar story to the overuse of DDT in the 1950s/1960s, so graphically illustrated in Rachel Carson’s book “The Silent Spring”. Back then, a whole raft of species accumulated DDT, many geographically distant from the area of application. Now it is animals other than rats and house mice that are being poisoned by rodenticide. Why do we never learn?

Back in the 1980s, a colleague once noted that whenever a pest controller landed up in court, ‘it was a dog that died’. Unprotected baits proved very attractive to many species that found them, particularly dogs. Even if baits were protected, only animals that were bigger than rats could be excluded, not those that were smaller e.g. outdoor living mice and voles. It was hardly surprising that increasing levels of anticoagulants were being observed in predators of rats and mice, particularly in predatory birds that were not going to be eating the bait itself. It was clear that rodent control practices were leading to both primary and secondary poisoning of unintended victims.


In the 1980s, unprotected baits proved very attractive to many species that found them, particularly dogs.


By the 1980s, resistance by rats to anticoagulants was becoming a significant problem in many parts of the country. This further exacerbated the problem to wildlife. Baiting continued even though it was failing to achieve control. At some sites, increasingly large quantities of bait were being laid to try and overcome the problem, rather than recognising resistance for what it was and changing to a different control strategy. More and more rats, dosed up with anticoagulant, were active for longer and in the food chain for longer, greatly increasing the likelihood of secondary poisoning.

By the turn of the century, it was becoming clear that practices had to change. HSE’s stark warning to users within agriculture, game keeping and public health, was to ‘self-regulate’ or HSE would… and we may not like the outcome!

It is not the intention of this article to go over the changes in working practices that have been introduced, all of us now will either be certificated or working under a farm assurance scheme. The purpose is to highlight how the Campaign for Responsible Rodenticide Use (CRRU) code of practice, if applied diligently, will bring about a halt to the year on year increase in the level of SGARs in non-target bird and mammal species.  Once levels have plateaued, attention can focus on beginning to reduce these levels.

The CRRU code encourages users:

  • To consider the potential consequences of any rodent management exercise by undertaking environmental assessments prior to each such exercise. Which non-target species might your activity affect?
  • To consider all possible methods of control, placing priority on habitat management first and chemical options last – the ‘hierarchy of rodent control’. If you don’t use rodenticide then you will not poison wildlife, domestic and companion animals.
  • If rodenticides are selected, they are to be applied so as to minimise the opportunity for non-target animals to access them.
  • If rodenticides are used, the objective is to seek eradication of the target infestation as quickly as possible and then to remove any surplus rodenticide from the environment. Permanent baiting becomes the exception, not the rule. The opportunity for non-target animals to access the bait is greatly reduced.
  • During and following a rodenticide treatment, rodent carcases must be actively searched for, collected and disposed of. The opportunity for predators and scavengers to eat poisoned carcasses is greatly reduced.


We don’t have long. To borrow a term used by M Barnier of the Brexit negotiations ‘the clock is ticking.’ The success (or otherwise) of the ‘campaign’ is already being assessed. It is vital that all of us who have been through the additional rodent management training do not view it just as a means to get ‘a ticket to use rodenticides.’ The content of these courses may have seemed controversial but unless the CRRU code of practice is taken seriously, we may yet lose some very valuable products.


If you're interested in learning more about the safe and effective use of rodenticides, check out our training courses.


Richard Strand is a zoologist who made his career in pest management. He was Executive Director of the British Pest Control Association (BPCA) for 18 years and President of the Confederation of European Pest Control Associations (CEPA). For the last 10 years he has been an Instructor and External Verifier for Lantra for pest management related subjects.


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