Rodenticides & Mice: Here’s What You Need to Know

It’s clear why you shouldn’t use rat poison, also known as rodenticides, against rats — rats are showing a serious immunity to most forms of rat poison, meaning that it just doesn’t work to get rid of them. Fewer mice are displaying this trait, but it still could be the case that mice in your building are immune to whatever chemical removal approaches you use.

Even if the mice in your building are not immune to the effects of rodenticides, we don’t recommend it as a pest removal method.

Here’s why . . .

You have no control over where that poison ends up. Mice might eat it. Other animals might eat it. Remnants of the poison could be deposited into the great outdoors in the feces of mice (and other animals) who have consumed it, and crumbs and leftovers of that poison could end up contaminating various things — water sources, soil, vegetation, etc.

Let’s just assume that you have an infestation of mice that are not immune to the toxic properties of rodenticides; you have absolutely no control over where the dying mice go, or where they die, or what happens to the carcasses. Poison doesn’t encourage the mouse population to leave your property. Instead, it just leaves a string of dead mouse carcasses all over the place. As you can imagine, this poses serious hazards to health, will kick up a bad smell after a short time, and just makes your job all the more difficult — you will need to locate, remove, and then dispose of every single mouse carcass that is hidden in and around your home.

In fact, exactly the opposite happens when you attempt to use poison to get rid of mice. Mice need to repeatedly eat the poisoned bait in order to get the full effects, so if they only eat a little bit and then move on, they might not consume enough to actually kill them. In these cases, the mice can become sick, weak, and vulnerable as a direct result of the poisonous bait, but still not die. They won’t die until they are so weak and vulnerable that they can no longer feed or take care of themselves, then suffer with the effects of dehydration, starvation, hyperthermia, overheating, and perhaps even predatory attack, such as that from a cat, dog or other domesticated animal. Being weak and vulnerable, the mouse is less likely to be able to scamper away and save itself when attacked.

Whether you’re attempting to cull a nest of mice or a nest of rats, using rodenticides (poison) isn’t a humane approach. In most cases, the poison isn’t enough to actually kill all of the rodent population, simply maiming them. In the case that the poison does work to kill the mice or rats, it takes a long time, usually as a result of massive internal bleeding. This is not a humane or quick death by any means, and we highly recommend avoiding it.

How do you know where those mice are going to go when they feel sick enough to die? There’s a pretty good chance they’ll head straight for the nest, or close to it, but if you haven’t located that nest yet (there could be many in one property), you’re going to have a hard time locating the carcasses to then remove and dispose of them. This could result in a number of actual holes in the wall as you make your way from room to room desperately trying to remove them. If you don’t remove them, the smell will get very bad, and the carcasses are also likely to attract other pests, such as flies.

Let’s say that the poison you’re using doesn’t work to kill the mice on your property — you’re still going to have mice. The longer they’re there, the more they will reproduce, and the more mess, smell, and damage they will cause. Going back to the point we made previously about attracting other pests, including flies, you could also attract other scavengers — animals that prey on mice — including snakes.

The story doesn’t get much better if your rodenticides DO work to kill mice. You’re going to have lots of dead or dying mice in the area which are going to be an easier meal for any predators. Unless you can find and then dispose of those carcasses or half-dead mice, they’ll work as an attractant for other, larger animals. Lots of animals prey on mice, both dead and alive, including foxes, coyotes, snakes, owls, eagles, and more.

If a weak mouse has consumed poison — the reason behind its weakness — it is not only more likely to be attacked by a predator (sensing its weakness), it is also more likely to pass on the effects of that poison. It’s the same story for an already dead mouse that has been poisoned.

The poison doesn’t just disappear from the mouse’s body because it is dead. It will still be present, in the flesh of the animal, as well as in the digestive system. If a predatory animal consumes that mouse, they are then consuming what poison is left in the mouse’s body. With enough poison, the predatory animal could then suffer with the effects of secondary poisoning. This is enough to kill other animals, including domesticated animals and agricultural animals. There have even been cases of very sick vultures, poisoned after feasting on eating poisoned rats.

Poison causes more problems than it solves in almost every single case, so we cannot personally recommend it to you as a successful and effective method of rodent control. We don’t recommend using poison in any way, not even in conjunction with other methods.

What we do recommend, however, is killing those rodents using traditional snap traps. The outcome is usually much more positive providing the traps are positioned correctly, and you are left with fewer problems to worry about. You’ll know where the carcasses are — still in the trap. You won’t accidentally cause secondary poisoning to another animal, such as a local pet cat. There’s also no fear of accidentally contaminating water sources or soil.