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Rodenticides can harm wildlife; please use carefully
Throughout California, the careless use of poison baits used to control rodents has injured and killed numerous wild animals and pets. This is because scavenging birds like owls, hawks, and predators such as raccoons, foxes, skunks and coyotes that eat dead or dying rodents that have consumed these baits will also be poisoned.
Pets will also eat dead or dying rodents and unprotected bait. You can protect both pets and wildlife by reading – and following – the label directions of any rodent baits you purchase, and only purchasing those that are legal for the pest you are trying to control.
Protect your wild neighbors and pets from accidental poisoning. Use all pesticides very carefully and follow all label directions, or chose organic or mechanical pest control methods.
Rodenticide Baits: Frequently-Asked Questions
Q. How do rodent baits harm wildlife and pets?
A. It's possible for wildlife and pets to consume the poison directly. However, it's more likely that these animals have received a secondary exposure. A secondary exposure occurs when wildlife or pets consume dead or dying rodents that have eaten the rodent bait. Wildlife that can be affected by secondary poisoning include owls, hawks, other scavenging birds and predators such as raccoons, foxes, skunks and coyotes.
Q. How can I protect wildlife and pets, but still control rodent pests?
A. Rodent bait users must follow label directions carefully. Some rodent baits, for example those that contain the active ingredients chlorphacinone and diphacinone, are legal to use in outdoor areas. These products can be used to control field rodents such as gophers, voles and ground squirrels. Other rodent bait products, such as those that contain the active ingredients broadifacoum, bromodialone or difethialone, can only be used to control rodents found within structures, like rats and mice.
- Read product labels carefully before using any pesticide, and follow directions exactly.
- Check daily for dead rodents. Wearing gloves, collect the carcasses as soon as possible, place in plastic bags and dispose in garbage cans with tight lids that other animals can't open. Always wear protective gloves when handling any dead animal.
Q. Where can I get the rodenticide with chlorphacinone and diphacinone?
A. These products are sold at many hardware, nursery and farm supply stores. Depending on the county, they may also be sold by the county agricultural commissioner's office.
Q. Why are chlorphacinone and diphacinone safer to use in open spaces?
A. Chlorphacinone and diphacinone are less toxic to mammals, and are eliminated rather quickly from the bodies of animals that ingest them. These products generally require multiple feedings before killing rodent pests.
Q. What kind of rodenticides should I NOT use in the yard, away from buildings?
A. Over-the-counter rodenticides, such as d-Con®, that contain the active ingredients brodifacoum, bromadiolone or difethialone. These can only be legally used to control rats and house mice in and around structures. It is illegal to use these products in open areas such as pastures or fields.
Q. Why is brodifacoum so dangerous for wildlife and pets?
A. Brodifacoum, bromodialone and difethialone pose a greater secondary toxicity risk to wildlife and pets than products that contain chlorphacinone and diphacinone. These products are more toxic to mammals, stay longer in the bodies of animals that ingest them and can kill with a single feeding. Their residues are most likely ingested by scavenging dead rodents. Deer are sometimes attracted to the pellet form of brodifacoum.
Q. How do these rodent baits work?
A. Both types of rodenticides are anti-coagulants. Animals that ingest them die from internal hemorrhaging (bleeding).
Q. How do you know rodent baits are poisoning wildlife?
A. Since 1994, CDFW's Pesticide Investigations Unit has confirmed at least 136 cases of wildlife poisoning from anticoagulant rodent baits. Brodifacoum was the poison most frequently detected. Animals harmed include coyote, gray fox, San Joaquin kit fox, raccoon, fox squirrel, bobcat, red fox, mountain lion, black bear, Hermann's kangaroo rat, golden eagle, Canada goose, great-horned owl, barn owl, red-shouldered hawk, red-tailed hawk, Cooper's hawk, turkey vulture and wild turkey.
Since animals typically retreat to their dens, burrows or other hiding places in the final stages of anticoagulant poisoning, the number of non-target wildlife killed by these compounds may be much greater than we know. CDFW researchers have found that most birds and mammals killed by anti-coagulants are found in areas adjacent to urban development.
Q. Can I control rodent pests without using poison baits?
A. You can discourage some rodents from moving in by keeping grasses mowed at no more than two inches or by disking around sites that need to be protected. (See Vole Control, below.)
Q. I found a dead raccoon (or other small wild animal) in my yard. What should I do?
A. First, do NOT touch it bare-handed. Wildlife can carry diseases and parasites, so always wear protective clothing – especially gloves – before handling dead or dying animals of any kind. If you're in an urban or suburban area, call your city or county animal control office with detailed information about the animal's appearance and condition. Even if they don't have the staff to come retrieve it, they need to know about it, as the one you found may not be the only one.
Q. If I think my pet has been poisoned, what should I do?
A. If your pet is having seizures, is unconscious or losing consciousness, or is having difficulty breathing, phone ahead and take your pet immediately to your local veterinarian or emergency veterinary clinic.
Rodent baits are often used to control voles. Their populations tend to be cyclical and once established, vole colonies are not easy to control.
One of the most effective ways to discourage voles from moving in is to simply mow grasses down to no more than two inches or disk around sites that need to be protected. Either action will reduce or eliminate their preferred habitat. Often, if you don't control the vole population, there may be little you can do about it. The secret is to protect sensitive sites – such as gardens – by mowing or disking the area before the population gets too high.
If you must use a rodent bait to control voles, only use those baits intended for field rodents. Their labels will identify chlorphacinone or diphacinone as the active ingredient. Baits should only be used in small treatment areas and the areas should be checked daily for dead rodents.
With very high vole populations, rodent baits may ultimately have little effect. The best approach is to protect sensitive sites – such as gardens – by mowing or disking the area before the population gets too high.