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Rodenticide

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Rodenticides are chemical substances manufactured specifically to kill rodents. While many people call them "rat poison," these chemicals are used to control a wide variety of animals. This includes mice, woodchucks, chipmunks, porcupines, nutria, beavers, and voles.

Rat Poison
Rat Poison

Because rodents cannot vomit, they often exhibit "poison shyness." They tend to sample new food and wait to see if it makes them or their companions sick. To overcome this, many rodenticides are designed to require multiple doses before they become lethal.

Tree squirrel eating bromadiolone tablets from a rodent bait station
Tree squirrel eating bromadiolone tablets from a rodent bait station

One major class of rodenticide is the anticoagulant. These chemicals work by blocking the vitamin-K cycle in the body. The body uses vitamin K to produce essential blood-clotting factors, specifically coagulation factors II (prothrombin) and VII (proconvertin). When these factors are blocked, the animal cannot clot its blood properly. Massive doses of certain anticoagulants, like 4-hydroxycoumarin, also damage tiny blood vessels called capillaries. This increases permeability and causes internal bleeding. The process is gradual and takes several days. Eventually, the rodent suffers from hemorrhagic shock or severe anemia and dies.

Anticoagulants are categorized into different generations based on their strength. First-generation anticoagulants generally require higher concentrations, usually between 0.005% and 0.1%. They require consecutive intake over several days to reach a lethal dose. Second-generation anticoagulant rodenticides, or SGARs, are much more potent. They are often applied in much lower concentrations, between 0.001% and 0.005%. These "superwarfarins" can be lethal after a single ingestion. They are also effective against rodent strains that have become resistant to first-generation versions.

Rattenkoederbox 4521
Rattenkoederbox 4521

Another type of rodenticide is the metal phosphide. These are fast-acting and usually kill within one to three days of a single dose. A common example is zinc phosphide, which is added to bait at concentrations of 0.75% to 2.0%. When the rodent eats the bait, the acid in its digestive system reacts with the phosphide. This chemical reaction generates a toxic gas called phosphine.

5654-Linxia-City-market-rat-poison-vendor
5654-Linxia-City-market-rat-poison-vendor

These baits have a strong, pungent garlic-like odor. This smell may attract rodents but often repels other mammals. However, birds like wild turkeys may not notice the smell and could accidentally eat the bait.

Some rodenticides use vitamins to cause harm, specifically vitamin D. Chemicals like cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2) are used for this purpose. These vitamins affect how the body manages calcium and phosphate, a process called homeostasis. In large doses, they cause hypercalcemia, which is an excessive amount of calcium in the blood. This high calcium level causes the body to absorb more calcium from food and move it from the bones into the blood.

Rat Poison
Rat Poison

This can lead to the mineralization of soft tissues like the kidneys, stomach wall, and lungs. It also causes heart problems and kidney failure.

Scientists sometimes use a process called synergism to make poisons more effective. This occurs when two substances are mixed to create a total effect that is greater than the sum of their parts. For example, mixing calciferols with anticoagulants creates a much more toxic result. This allows manufacturers to use lower, less expensive concentrations of calciferols while still achieving a massive toxic effect. This method is used in modern products like Sorexa CD, which combines difenacoum with cholecalciferol.

Safety is a major concern when using these chemicals. Many rodenticides are toxic to non-target animals, including dogs, cats, and humans.

Nontarget affected animals
Nontarget affected animals

There is also a significant risk of secondary poisoning. This happens when a predator, such as a hawk or a cat, eats a rodent that has already ingested poison. While metal phosphides have a low risk of secondary poisoning because they do not accumulate in tissues, other types like SGARs can be more dangerous. Because single-dose anticoagulants bind closely to enzymes in the liver, they can be stored in the body for a long time.

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🖼️ Images & Media (7)
File:Rattenkoederbox 4521.jpg
Rattenkoederbox 4521.jpg
File:Rat Poison.jpg
Rat Poison.jpg
File:5654-Linxia-City-market-rat-poison-vendor.jpg
5654-Linxia-City-market-rat-poison-vendor.jpg
File:A Box of Blue Rat Poison.jpg
A Box of Blue Rat Poison.jpg
File:CPS141ratpoison.jpg
CPS141ratpoison.jpg
File:Tree squirrel eating bromadiolone tablets from a rodent bait station.jpg
Tree squirrel eating bromadiolone tablets...
File:Nontarget affected animals.jpg
Nontarget affected animals.jpg
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