As soon as fall approaches the possibility of a rat infestation increases too, which means usage of rat poison, also known as rodenticides, goes up as well. However, what many of us are unaware of is that rat poison doesn’t just kill rats alone- their impact goes high up in the food chain.

Rat poison or rodenticide is actually a pesticide that kills rodents. Rodents include not only rats and mice but also squirrel, chipmunk, beavers, nutria, porcupines, and wood chunks. Currently, there are four different types of rat poison available in the market; anticoagulants, neurotoxins, cholecalciferol, and zinc phosphide. The thing with any type of poison targeted towards a specific species is that many times other non-target species also have to suffer the consequence. Rat poison, though aimed at killing rats, cause severe health damage, direct death on ingestion and secondary poisoning resulting in death in non-target wildlife. Numerous cases of animal death have been reported as a result of secondary poisoning, caused by the process of bioaccumulation of rat poison in rodent carcasses and causing poisoning in rodent-eating predators. In recent years, animals like hawk, owl, foxes, coyotes, mountain lion and even fishes have been reported as endangered as a result of secondary poisoning from rat poison. In California’s San Francisco Bay Area, TheSan Joaquin kit fox, Alameda whipsnake, Swainson’s hawk and salt marsh harvest mouse are species at risk of poisoning by rodenticides

The Different Types of Rat Poison 

Rat poison can be broadly divided into two main categories; Anticoagulants and non-anti-coagulants. Currently, four different types of rat poison are sold in the market; anticoagulants, neurotoxins, cholecalciferol, and zinc phosphide- the last three being non-anticoagulants. Vitamin k is an essential compound that helps in clotting blood. Human and animal bodies require vitamin k, among other purposes, to help blood clot and prevent excessive bleeding.  This much essential vitamin is recycled in the liver with the help of a special enzyme Anticoagulants work by inhibiting the coagulation of blood by preventing the function of this enzyme and cause internal bleeding, resulting in death within 3-10 days, in rats or any animal that ingests the poison or the poisoned rats. Meanwhile, the non-anticoagulant category of rat poison usually kills in a shorter time span. The main non-anticoagulant rat poison in use are neurotoxins, cholecalciferol, and zinc phosphide. Neurotoxins target rats by causing swelling in the brain that leads to paralysis and, eventually, death. Cholecalciferol, one of the most potent rat poisons, increases blood calcium levels to life-threatening levels and may result in kidney failure. Apart from targeting rats, Cholecalciferol is also poisonous to cats, dogs, cows, horses, and birds. While zinc phosphide, upon ingestion, converts to phosphine gas which is then absorbed into the bloodstream and captured by the liver and the lungs. This Phosphine gas results in lung dysfunction, vomiting, weakness, collapse, and even death.

The Impact of Rat Poison High Up in the Food Chain

 Rat poison has put other living things from birds to pets and even humans at tremendous risk. The rat poison effects in two ways on other living things; primary poisoning and secondary poisoning. Primary poisoning occurs by the direct ingestion of the rodenticide by a living thing. The extent of poisoning depends on the different type of rat poison being used i.e. anticoagulant or non-anticoagulant. Secondary poisoning usually occurs when one organism eats another organism that has been poisoned. Animals that prey on poisoned rat carcasses also ingest the rat poison along too. However, whether any harm occurs due to secondary poisoning depends on the extent of the toxicity of poisoning and the number of feedings on the poisoned carcasses. Secondary poisoning is only harmful if the toxicity of the poison is sufficiently high.

Impact of Rat Poisoning on Pets- Cats and Dogs

Cats and Dogs by nature are pretty curious creatures, no wonder they often end up ingesting things they shouldn’t- one of them being rat poison. The most common rat poisons include Anticoagulants, Cholecalciferol, Bromethalin, and Phosphides. Depending on the different types of rat poison, the symptoms of poisoning in cats and dogs may vary. 

Anticoagulants

Anticoagulants inhibit the production of vitamin k, thereby preventing blood clotting and causing internal bleeding which, eventually, cause death. It usually takes 3-5 days for symptoms to start showing in a dog that has ingested an anticoagulant rodenticide. Common warning signs to look out for are lethargy, exercise intolerance, coughing with or without blood, difficulty breathing, and pale gums. Some poisoned pets may also show these less common signs including vomiting, diarrhea, nose bleeds, bruising, bloody urine, and bleeding from the gums. In comparison to dogs, cats are more resistant to this type of poison. Once the symptoms are identified, treatment of vitamin-k1 for 30 days usually serves as the best antidote.

Cholecalciferol

This is one of the most dangerous and most difficult to treat rat poison. It elevates blood calcium to life-threatening levels, resulting in acute kidney failure. Symptoms include decreased appetite, increased thirst and urination, uremic breath, weakness, lethargy, and possible kidney failure within two days of ingesting the poison. Cholecalciferol poisoning has almost no antidote and a small dosage of this could be extremely lethal.

Bromethalin

Ingestion of This poison results in brain swelling as a result of uncoupling oxidative phosphorylation. Common symptoms include impaired movement and coordination, vomiting, seizures, decreased appetite, paralysis, possibly coma and eventually death. Symptoms usually start appearing within the first 2 hours but may be delayed as long as 36 hours. The severity of the condition depends on the amount of toxin ingested. Cats usually show greater sensitivity towards bromethalin than dogs. Generally, a 2.5 mg/kg dose of bromethalin is considered toxic for dogs. 

Phosphides

While these are typically used to kill larger animals y, they may make their way into rat poison. This poison is not only dangerous for your pets but also your home and yourself. Once ingested, phosphides release toxic phosphine gas which is harmful to both the pet and pet owner if inhaled. It is recommended to not feed your dog anything in case of phosphide toxicity as food in the stomach will cause more phosphine gas to release. Common symptoms include seizure, bloating, shock, vomiting, abdominal pain, and liver damage. 

Impact of Rat Poisoning on Birds

The devastating impact of rat poison on wildlife has been a cause of concern recently. Not just animals, but even raptors (birds of prey) are not sage from it. According to a study by Tufts University found 88 percent of raptors have been found with rat poisoning. In California’s San Diego County, rat poison was found in 92 percent of raptors (bird of prey).a study in new york revealed that rat poison was found in 49 percent of 12 species of necropsied raptors and 81 percent for great horned owls. According to a Norwegian study, analyzing rat poison level in dead predatory birds, active ingredients of rat poison have been found in the liver of as 70 percent of golden eagles and 50 percent of eagle owls examined in a Norwegian study were found to have active ingredients of rat poison in the liver. The anticoagulant found in rat poison prevents blood clotting and may lead to internal bleeding. However, g however, until the body’s store of vitamin K is not exhausted t poison doesn’t show any signs or symptoms. As a result of which predatory eagles end up ingesting m poison in the form of poisoned rats, leading to an accumulation of poison in their bodies and an eventual death. While different bird species react differently to the different types of poison, there is a risk of poisoning at levels lower than 100 Nanograms per gram of liver tissue. 

In conclusion, all forms of rat poison have a negative impact on wildlife.  While the severity of harm caused by rodenticide depends on the type of rat poison being used, all types of rodenticide do cause some extent of poisoning that goes high up in the food chain.

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Dusty Showers has been in the urban nuisance wildlife and pest control field since 1993. Taught by Garon Fyffe, a pioneer in humane nuisance wildlife management, Dusty has a passion for finding humane solutions to human & wildlife conflicts. Dusty was the only individual invited by the Florida Fish & Wildlife Commission in the lat 1990's to help write legislation for legal protection of Florida bats. With an instinct for solving wildlife, Dusty found pest control to be an easy "add-on interest". Dusty started his first business "Animal Instincts Wildlife & Pest Management" in the Tampa Bay, Florida area in 1995. Eventually selling Animal Instincts in 2002, Dusty went on to start Creepy Creatures Termite and Pest Control in 2009, which he still owns and operates today in Palm Harbor, Florida.

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