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Sad Reminder About Rodenticide Use

rodenticide boxWe are saddened to hear about the recent passing of one of our local mountain lions. You may have seen past articles in local media including the Los Angeles Times, Ventura County Star, and the Acorn.

Anti-coagulant poisons have been linked to numerous past deaths of wildlife such as mountain lions, bobcats, and hawks who prey on rodents as a food source as well as cats and dogs who eat the sick rodents. The Santa Monica Mountains Fund has been leading an effort locally to eliminate the use of anticoagulant rodenticides to prevent these deaths. The Thousand Oaks City Council voted unanimously on April 14, 2015 to discontinue the use of anticoagulant rodenticides in operations and maintenance of municipal facilities and landscape, except under circumstances of extreme risk of danger to the health of our citizens or damage to infrastructure. In addition, it urged businesses and residents to stop using anticoagulant rodenticides and businesses to stop selling them. A couple of years ago, the City contacted all HOAs in Thousand Oaks to encourage them to discontinue use of the poisons and remove bait boxes from their premises, and provided references to resources and effective alternatives to poisons. Neighboring cities including Malibu, Agoura Hills, Calabasas, and Westlake Village have also passed resolutions urging businesses and residents to discontinue the use of anti-coagulant rodenticides. 

First-generation anticoagulant rodenticides require rodents to consume the bait for several consecutive feedings for delivery of a lethal dose. There are three US EPA-registered first-generation rodenticides, including warfarin, chlorophacinone, and diphacinone. The first-generation compounds are excreted fairly quickly by mammals, usually within a week. The second-generation anticoagulant rodenticides (SGARs) are substantially more potent than the first-generation compounds, and a lethal dose can be ingested in a single feeding. SGARs are not excreted easily, persisting in bodily organs such as the liver. Some SGARs are especially problematic to birds and mammals.

poisoned CATEPA studies indicate that the first-generation anticoagulants are less hazardous than the more highly toxic and persistent second-generation anticoagulants. SGARs compounds are much more likely to poison predatory wildlife that eat live or dead poisoned prey and have a higher risk of severe poisoning for children, pets, and other non-target wildlife. The second generation anticoagulants are the only ones banned for consumer use, but however it has been determined that 1st generation anticoagulants are also doing harm. The use of any rodenticides poses a poisoning risk to children, pets and wildlife. That is why the City supports nontoxic forms of control.

We recently wrote an article on more ways to avoid the use of rodenticides to control rodents around your home, and developed a helpful brochure, available on the City website, about second generation anti-coagulant rodenticides.  If you find good resources or links on safe rodent control, please share them with your friends and family on your social media channels, in addition to forwarding this article to them.

If you suspect an HOA, school, business or resident is using first or second-generation rodenticides, contact them to inquire what they are using, or what their pest control company is using. Keep in mind that not all bait in bait boxes contain anticoagulants, kill traps and non-anticoagulant rodenticides may instead be used in the bait boxes.  These include bromethalin, cholecalciferol, and zinc phosphide, which are US EPA-registered and frequently used in controlling pest rodent populations. The potency of these rodenticides is highly variable, with rodent mortalities typically occurring several hours to days following ingestion of a lethal dose.

As a neurotoxicant, bromethalin poisons the central nervous system and ultimately causes respiratory distress following ingestion of a single dose. Cholecalciferol, the biologically active form of vitamin D, is completely nontoxic in small amounts, but massive single doses or prolonged low-level exposure can prove toxic. Ingestion of excessive amounts of cholecalciferol induces hypercalcemia (elevated blood calcium levels), which ultimately results in heart problems and kidney failure. Zinc phosphide, which functions to liberate toxic phosphine gas upon interaction with stomach acid, is highly toxic and can lead to rodent mortality within hours of ingestion. Unfortunately, zinc phosphide can also poison birds, such as hawks and owls, following ingestion of treated baits.

In addition to our rodent control web page, here is another good reference for safe rodent control:
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