Winter can invite household nuisances like mice and rats inside along with unwelcome gnawing habits, putrid droppings and disease. But as you look to eradicate vermin from your house this winter, The Raptor Center at the University of Minnesota invites you to take a moment and pause.
Your choice between rat poison and an old-school snap trap could impact human, pet and wildlife health.
Commercial and consumer rodent poisons frequently result in unintended poisonings. More than 10,000 children suffered from direct exposure to rodenticides nationwide prior to a recent tightening of protections by the Environmental Protection Agency (EPA). Pet and wildlife poisonings are also recurrent, with The Raptor Center seeing occasional suspect cases of secondary poisonings.
In 2008, the EPA unveiled new regulations to prevent the most common U.S. rodent poison risks. The rodenticide class now banned for retail to consumers is known as “second-generation anticoagulants,” which work by preventing the body from clotting blood and fully healing itself. Days can pass between the time a mouse or rat was poisoned and the rodent’s death. In the meantime, raptors, including Minnesota’s great horned owls, short-eared owls, and red-tailed hawks can ingest the poisoned animal and suffer similar poisoning effects.
“Studies have shown that a high percentage of raptors in rehabilitation show evidence of anticoagulants in their livers,” said Julia Ponder, D.V.M., executive director of The Raptor Center at the University of Minnesota. “Because we don’t know with certainty if rodenticide poisoning plays a role until after death, rodent-consuming birds receive vitamin K when excessive bleeding or bruising is present.”
Vitamin K counteracts the active ingredient in many poisons – an anticoagulant – over the course of one month, but can still leave birds more vulnerable to poisoning the next time around.
While new EPA guidelines protect children and pets by restricting the intensity of poisons available directly to consumers, commercial rodenticide companies can still apply second-generation anticoagulants when contracted.
“It’s important to call around and learn what your commercial company, neighborhood or condominium association is using,” said Ponder. Second-generation anticoagulant poisons brodifacoum, bromadiolone, difenacoum and difethialone are well-known wildlife offenders. While these poisons kill rodents effectively by requiring only ingestion of only a single dose to cause death, they also have the most severe trickle-down effects.
First-generation anticoagulants, by contrast, generally pose a lesser risk to wildlife health and can serve as a slightly safer alternative. This poison type requires multiple ingestions by a rodent to prove effective, and is therefore somewhat less potent should it carry over to raptors.
Photo: Flickr user Rennett Stowe/CC 2.0/flic.kr/p/644zVk
“It’s about striking a balance when it comes to rodent control,” said Ponder. “The most effective poisons are unfortunately also the greatest risk to wildlife. It’s important to consider all your rodent-control options – including non-poisons.”
When Ponder discovers an unwanted mouse in her house, she uses an old-school wooden snap trap.
Learn how rodent poisoning can ripple through an ecosystem – such as this one in the Santa Monica Mountains – in the National Park Service graphic below. (Click to enlarge.)
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