Rodenticides are potentially toxic to any species of bird or mammal—including children and pets. Rodenticide poisoning has been reported in many wild mammals including white-tailed deer, raccoons, gray squirrels, chipmunks, red foxes, skunks, opossums, prairie dogs, and badgers. Wild birds reported with rodenticide toxicity include bald eagles, golden eagles, peregrine falcons, red-tailed hawks, great-horned owls, snowy owls, screech owls, turkey vultures, wild turkeys, and crows. The poisoning of these species is generally unintentional, secondary poisoning caused by eating an animal that was intentionally poisoned because it was considered a nuisance or undesirable—such as rodents under a bird feeder. Nonetheless, these animals are being needlessly killed for the sake of convenience.

The two types of rodenticides are: Anticoagulant rodenticides which work by interfering with the activation of Vitamin K, a critical component in the production of blood clotting factors in the liver. An animal that ingests it will eventually hemorrhage and bleed to death. The second type of rodenticide are non-anticoagulants which are more variable and are dependent on the chemical and dose. The clinical signs of ingestion include: rapid onset of seizures, muscle tremors, limb weakness, ataxia, neurologic signs, respiratory paralysis, anorexia, nausea, vomiting, diarrhea, and lethargy.

The scenario goes something like this: rats are gathering under your bird feeder eating the seeds that have fallen to the ground. You want them gone! So what should you do?  Mostly it is what you should NOT do and why! Rats appear only when food is available. You are the source of that food. Feeding backyard birds is a pleasurable avocation for many, but birds are not tidy and seeds fall to the ground making an enticing buffet for ground dwelling creatures.

You have set the stage for rats to appear, as well as other opportunistic scavengers that will clean-up your mess. The best thing you could do is clean up the spilled seeds and in a short time the problem would be remedied. All too often a trip to the hardware store to purchase poison is considered the solution to the problem. So you lay poison out to kill the rats…and everything else that gets tangled in the thread created when it is used.

You have now set in motion a chain of destruction within your local ecosystem, and beyond. Rats are at the bottom of the food chain, reliant on found food and are part of the diet of birds of prey and small species predators. Birds of prey—hawks and owls feed on the rats who have ingested poison and the poisoned flesh then in turn kills the birds. Also foxes and coyotes feed on the poisoned rodents and possibly the poisoned bait, and they have now been eliminated for your local ecosystem.

Since the predators already manage the rodent population you have created a lethal redundancy impacting far more than the scavenging rats.

Sources: Commonwealth of Pennsylvania Game Commission; Cornell Wildlife Health Lab