Evolution is a characteristic of all organisms. And just like man, other living things evolve to ensure their survival or defend against threats. The population expansion we’ve experienced over time means that areas previously unoccupied by human beings are now budding residential areas. With this residential expansion, humans have now built houses in the regions that wildlife once dominated. So today, we have man coexisting with wildlife (including pests) in different places.
We have attempted pest control in many ways since pests can be troublesome. One of the more obvious routes to pest control is killing the pests around your house, and poison is usually a very effective tool. However, the effectiveness of poisons seemingly dropping against rats across the globe begs the question: can rats get immune to poison?
In the 1950s, scientists discovered that rats were becoming resistant to the effects of poison. By 2012, studies in the UK showed that almost 75% of rats in the West of England were resistant to conventional poison. A biological, genetic mutation has helped some rats become immune to the effects of poison.
What Classifies as Rat Poison?
A rat poison can be anything capable of causing death or significant illness in rats when it gets into their systems. Rat poison is also known as rodenticides. Some ingredients can also be home made to repel or kill rats. Over the years, these substances have come in different forms, and the different types work best in different situations.
What are the Different Types of Rat Poisons?
To fully understand rat poisons, how they work, and what might be best for you, let’s take a look at the different types of rat poisons:
- Anticoagulants: Anticoagulants are one of the popular types of rodenticides. We can trace its history to 1947. But it was finally registered in 1950 after scientists discovered warfarin (a type of anticoagulant) in moldy sweet clover that made a herd of cattle fall sick.
Anticoagulants work as blood thinners, preventing enzymes that enable the recycling of Vitamin K from functioning. When the recycling of vitamin K slows, blood clotting agents that prevent excessive bleeding will not act. With significant exposure to anticoagulants, even the internal reserves that enable blood clotting run out. The rodent dies from internal bleeding, severe anemia, or hemorrhagic shock.
First-generation anticoagulants (those developed in the 1940s and 1950s) like Warfarin, Diphacinone, and Chlorophacinone require multiple consumptions to constitute a lethal dose. On the other hand, second-generation anticoagulants can deliver a fatal blow after rats ingest them just once. These anticoagulants like Brodifacoum, Bromadiolone, Difethialone, and Difenacoum persist in the system of anything that consumes them. They can also be hazardous to scavengers that feed on anything already poisoned.
Overall, anticoagulants are very dangerous and can significantly harm birds, other mammals, children, and adults. But anticoagulants are also highly effective rat poisons, particularly second-generation anticoagulants.
- Hypercalcemia: Hypercalcemia rodenticides provide rats with excess values of Vitamin D to increase the calcium levels in the body. Naturally, Vitamin D and calcium are only necessary in small quantities. However, a hypercalcemia rodenticide will increase the calcium a rat absorbs from its food. High calcium will affect multiple internal organs after calcium crystals form.
Organs that might be affected include the heart, lungs, stomach walls, and kidneys. In most cases, a single dose of hypercalcemia rodenticides may kill a rat. However, it might take a few days or even a week before death.
To increase effectiveness and toxicity, some manufacturers combine hypercalcemia with anticoagulant rodenticides. When combined, a single dose is more effective than single doses of each when administered individually. However, hypercalcemia rodenticides are still quite harmful to other pets and mammals. When combined with anticoagulants, they are ultimately more deadly.
The main component in a hypercalcemia rodenticide is frequently cholecalciferol or ergocalciferol. With cholecalciferol, a 0.075% concentration is usually sufficient, while for ergocalciferol, you might need as much as 0.1%.
- Metal Phosphides: Metal phosphides are one of the oldest types of rat poison. They are highly toxic since a single ingested blow will most likely kill a rat, but death may come in 1 to 3 days. Metal phosphides, particularly zinc phosphides (the most common form of metal phosphides), have to be ingested by the rat with bait food. The phosphide reacts with acid already present in the rat’s digestive system to generate phosphine gas which is toxic to the rat.
Phosphides were popular before anticoagulants were invented and have still worked where rats have become immune to the effects of anticoagulant rodenticides. The phosphides typically emit a smell that discourages most mammals and pets (but not birds) from consuming them, making them relatively safe. There is also a very low risk of poisoning for a pet that eats a rat poisoned with phosphides.
A concentration of 0.75 to 2% of phosphides in the bait will be sufficient.
- Bromethalin: Bromethalin rodenticides combat rats who have grown immune to the effects of anticoagulant rodenticides. They are generally more lethal than anticoagulants, and bromethalin rodenticides might require just a third of the dosage size anticoagulants require to kill a rat. A single dose of bromethalin will be very effective.
This rat poison works by hindering the production of energy in the central nervous system cells. Subsequently, these cells swell, putting significant pressure on the brain and causing paralysis and death. Bromethalin will naturally cause death in 1 or 2 days and is very effective against a large rat population.
It’s also highly toxic to pets, wildlife, and humans. Even skin contact with the poison is moderately toxic, so you must take all appropriate precautions during application.
- Strychnine: Strychnine is another highly lethal rat poison. It is so deadly that it can kill rodents slightly bigger than rats, and you cannot use it above ground in most places. Most countries also allow only certified pet control professionals to purchase strychnine.
Rats can absorb this poison through their mouths or stomachs. After absorption, it prevents effective nerve signals in the muscles and boosts reflex irritability in a rat’s spinal cord. This results in a loss of motor functions and extreme muscular contractions or spasms. Symptoms of poisoning might be evident in the rat within 20 minutes.
It is also highly harmful to humans, pets, and other wildlife.
Thankfully, resistance to a specific poison does not mean resistance to the effects of all poisons. If you think the rats around you have developed an immunity to the rat poison you use, you should switch to a different poison type. However, how you apply the poison is also very important.
More importantly, all our technicians are licensed, and. We understand how urgent a pest problem can be, so we are available 24 hours a day and strive to provide you with our services within a day. 
