California’s rat poison bans aren’t working
For at least a decade, California has tried to restrict the use of rat poison so it stops killing all manner of creatures besides rats. So far, it hasn’t worked.
When a wild animal preys upon a rat that has ingested anticoagulant rodenticide, it can end up dead or sickened by the toxin as well. The poisoning continues up the food chain from predator to predator. Mountain lions, bobcats, foxes, coyotes, hawks as well as endangered species including the northern spotted owl and San Joaquin kit fox are among the wildlife that have been either killed by these rodenticides or made so ill that they can’t navigate their environment, hunt for food or dart across a road efficiently.
Anticoagulant rodenticides didn’t kill P-22, the beloved Griffith Park mountain lion, but they turned up in his system a couple of times — once causing a bout of mange for which he was lucky enough to receive treatment. Several different rat poisons were found in his system after he was euthanized in 2022, including diphacinone, a first-generation anticoagulant. Both of these rat poisons kill by causing internal bleeding. The older first-generation version is slower-acting, requiring the rat to feed on the poison several times before it is killed by it. The second-generation version kill rats more quickly.
Ten years ago the state prohibited the commercial sale of the more potent and fast-acting second-generation anticoagulant rodenticides, allowing them only to be used by professional exterminators. In 2020, the state Legislature decided to extend the ban to professional uses as well, except in some agricultural settings and in public health emergencies.
But the law still allowed consumers and professional exterminators to use first-generation rodenticides, which don’t act as quickly but still carry a powerful toxicity capable of sickening and sometimes killing the birds, mountain lions and other creatures that prey upon rats. A recent study of red-tailed hawks that ate prairie dogs poisoned with diphacinone showed signs of blood-clotting and trouble regulating their body temperatures.