Why rat and mouse poison poses different risks to dogs, cats and wildlife
Not all rat and mouse poisons are the same. Different active ingredients and bait concentrations can present very different risks to dogs, cats and wildlife. One product might reduce the risk of poisoning an animal that eats a poisoned mouse (for example) but may also pose a greater risk if a dog eats the bait directly. Therefore choosing a suitable rodenticide for a given job involves considering both the target pest being controlled, and what other animals may be on site that we want to protect.
This article assumes that rodenticide use has already been assessed as necessary and appropriate, after considering non-toxic alternatives such as proofing, removing food sources and trapping.
Using rodenticide inside a property also involves weighing up the potential consequences. A rodent that dies in an inaccessible area can cause an unpleasant smell that may persist for some time. However, where appropriate, rodenticide used alongside measures such as trapping can help achieve faster control, reducing the health and property risks associated with a prolonged rat or mouse infestation.
No rat or mouse poison is safe for pets to eat. Let’s make that clear from the outset. The aim is always to prevent pets and other non-target animals from accessing bait. However understanding the differences between products can add another layer of protection by helping a pest controller reduce the risks should an accident occur.
Our general guide to rat poison around pets explains how we plan and place treatments. This article looks more closely at active ingredients and how their toxicity figures can impact on product selection.
If you think your dog, cat or other pet has swallowed toxic bait, contact a vet immediately, even if your pet looks well. Keep the packaging or ask your pest controller for the product name and active ingredient. Do not wait for symptoms or try to calculate a safe quantity from figures online.
What does LD50 mean?
LD50 is a measure used to compare acute toxicity. It is the estimated dose that would kill 50% of a test population under specified conditions. For rodent baits, comparisons may be expressed as grams of bait per kilogram of an animal’s body weight. The lower the number, the more toxic the product is for a given species species.
It is not the amount an individual animal can eat safely. Serious illness or death can occur at lower doses.
The British Pest Control Association (BPCA) publishes the following cautionary estimates. Each figure represents grams of the specified bait per kilogram of body weight to deliver an estimated LD50 dose.
| Bait formulation | Dog LD50 | Cat LD50 | Rabbit LD50 | Chicken LD50 |
|---|---|---|---|---|
| Cholecalciferol, 750 ppm | 13.4 g/kg | 166.7 g/kg | 12 g/kg | Not listed |
| Difenacoum, 50 ppm | 200 g/kg | 2,000 g/kg | 40 g/kg | 1,000 g/kg |
| Bromadiolone, 50 ppm | 200 g/kg | 500 g/kg | 20 g/kg | 1,000 g/kg |
| Brodifacoum, 50 ppm | 5 g/kg | 500 g/kg | 5.8 g/kg | 200 g/kg |
Source: BPCA — Lethal Dose 50 (LD50): everything you need to know.
The differences are substantial. For instance, difenacoum and bromadiolone have much higher dog LD50 figures than cholecalciferol or brodifacoum – so are less toxic. The cat figures are show less toxicity compared to the dog figures. This is how what none target species are present can impact when choosing a product.
Note how care must be taken around rabbits, with comparatively high toxicity across all active ingredients.
Dogs and cats may encounter poison in different ways
A dog may investigate and eat bait it finds, including pieces moved by rodents. A cat may be less inclined to eat spilled bait, but a hunting cat may catch or eat a mouse that has fed on it. These are tendencies to consider, rather than guarantees about an individual pet. Cats can of course eat bait directly.
Body size matters too. Within the same species, a smaller animal generally needs to eat less bait to receive the same dose per kilogram of body weight. A small amount of spilled bait can therefore be more consequential for a small dog than a large one.
Cholecalciferol bait: balancing direct and secondary poisoning risks
Cholecalciferol is vitamin D3 used at a concentration intended to kill rodents. Toxic doses disrupt calcium balance, causing death.
Certain cholecalciferol products can provide relatively rapid control and a “stop-feed” effect: rodents stop feeding after consuming a lethal dose, potentially reducing the amount of bait eaten. Another advantage is a lower risk of secondary poisoning than with anticoagulant baits. Secondary poisoning occurs when another animal eats a poisoned rodent.
However, this advantage does not make the bait harmless if eaten directly. The BPCA comparison shows a relatively high toxicity for dogs with 750 ppm cholecalciferol bait. There is also no specific antidote, although veterinary treatment is available.
A product selected to reduce secondary poisoning risk may therefore present a different challenge where a dog is on site, and so this risk must be built into any treatment plan.
Anticoagulant bait: why the particular ingredient matters
Anticoagulants interfere with blood clotting. For the formulations shown in the table, 50 ppm difenacoum and bromadiolone baits have higher LD50 figures for both dogs and cats than 750 ppm cholecalciferol bait. This indicates lower toxicity in that comparison and can provide a greater margin if accidental ingestion occurs.
That advantage does not apply to all anticoagulants. Brodifacoum, for example, has a much lower dog LD50 and so is much more toxic.
Anticoagulants also have a specific antidote: vitamin K1, prescribed as part of veterinary treatment. Its availability is a useful consideration, but does not remove the need to prevent exposure.
The trade-off is the secondary poisoning risk. An owl, fox or other animal may eat a poisoned rodent, and anticoagulants can accumulate in animal tissues. Some rodent populations are also resistant to particular anticoagulants, leading to fail treatments. A bait that looks preferable from one toxicity comparison may be unsuitable if the rodent population have developed a resistance to that product.
What should I do if my pet may have eaten rat poison?
Call your vet immediately. Give them:
- The product name and active ingredient, if known.
- The approximate amount that may have been eaten.
- When the incident may have happened.
- Your pet’s weight.
Take the packaging or a photograph of the label if available. If a professional placed the bait, ask them for the product details straight away, without delaying your call to the vet.
Do not wait for signs of illness: symptoms can be delayed. Treatment depends on the product, so accurate identification matters.
Does a higher LD50 make a rat poison safe for pets?
No. A higher LD50 can indicate lower toxicity, but it does not make bait safe to eat.
Choosing the active ingredient is one part of designing a treatment. An experienced pest professional will consider the rodents present, likely local resistance, bait placement, pets and wildlife, and how the treatment will be monitored.
If you are considering using rat or mouse poison yourself, it is worth asking whether you fully understand the factors involved in choosing and using a suitable product. My personal view is that rodenticides are best left to trained professionals—although, as a pest controller, I appreciate I am not entirely without bias. Unfortunately, I regularly encounter unsafe use of DIY rodenticides by well-intentioned customers trying to resolve a problem themselves. The risks are not always obvious, and being able to buy a product does not necessarily mean knowing how to use it safely.
If you have pets at home, tell your pest controller before any rat or mouse treatment starts. At The Pest Company, we tailor treatment plans to the property, aiming to control the infestation effectively while minimising risks to people, pets and local wildlife.
