How rat poison affects animals high up in the food chain

February 24, 2016, 8 a.m.
A distracted barn owl perched on a post
Photo: duangnapa_b/Shutterstock

When we set out poisons aimed at one animal, sometimes it's many other animals that suffer the consequences. One infamous example is DDT, an insecticide that sent populations of many bird species plummeting in the mid-1900s. Today, the same is happening with rodenticides.

Aimed at killing mice, rats and other rodent pests, the poison can work its way up the food chain, causing the grisly deaths of hawks, owls, eagles, bobcats, mountain lions, coyotes, pet dogs and cats, and even predators far, far away from cities, such as fishers. The predators consume the poison when they consume the rodents that ingested poisoned baits.

Audubon Magazine writes, "Both first- and second-generation rodenticides prevent blood from clotting by inhibiting vitamin K, though the second-generation products build to higher concentrations in rodents and are therefore more lethal to anything that eats them."

The U.S. Environmental Protection Agency explains further that, "Second-generation anticoagulants also are more likely than first-generation anticoagulants to be able to kill after a single night's feeding. These compounds kill over a similar course of time but tend to remain in animal tissues longer than do first-generation ones. These properties mean that second-generation products pose greater risks to nontarget species that might feed on bait only once or that might feed upon animals that have eaten the bait."

In 2014, California banned direct-to-consumer sale of some types of rat poisons over concerns for wildlife. According to the Center for Biological Diversity, "Harm to wildlife from rodenticides is widespread: Poisonings have been documented in at least 25 wild species in California, including mountain lions, hawks and endangered San Joaquin kit foxes and northern spotted owls." That is only one state, however, and even in California the worst of the poisons are still available for commercial use.

Audubon points out there are safer alternatives, "including single- and multiple-entrance snap traps, electrocuting traps, glue traps (provided you use them only indoors and frequently dispatch stuck rodents), and even first-generation baits with these active ingredients: chlorophacinone, diphacinone, diphacinone sodium salt, warfarin and warfarin sodium salt."

Mammals, raptors and other animals are necessary for rodent control. Taking them out along with the rodents will present a much bigger problem in the long run than anything rodents may currently be doing. Keeping them around requires coming up with smarter, safer solutions to handle rodent infestations.

You can help by encouraging local and state legislators to look into the issue and ban rodenticide, and by looking into safe rodent control options for your home or business that avoid these harmful and long-term impacts.

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Jaymi Heimbuch is a writer and photographer at Mother Nature Network. Follow her on Twitter, Instagram and Facebook.