Rat poisons killing hawks, owls and others

Three adult Northern Spotted Owls like this one tested positive for rodenticides in their blood in 2012.  Photo by JoLynn Taylor
Whooo's poisoning me? Great Horned Owls are disproportionately represented in WildCare's data of positive rodenticide results. Photo by Melanie Piazza
Gray Foxes like this young orphaned patient represent the highest percentage of positive results. These little animals are fantastic rodent control, so their poisoning is extremely disturbing. Photo by Melanie Piazza
A healthy family of Gray Foxes in your yard are not only thrilling to observe, they provide free rodent control! Photo by Linda Campbell
Raccoons eat lots of rodents and will keep your property free of rodent infestations, unless they are poisoned. Photo by Christine Margle
A Red-tailed Hawk poisoned by rodenticide shows the tell-tale bleeding from eyes and nares that indicate anticoagulant exposure. Photo by Alison Hermance
Great Horned Owlets like these can easily be poisoned when their parents bring them a poisoned rodent. Help WildCare halt the use of these deadly poisons!
Rat at a bird feeder. Photo by Laura Lind Bring bird feeders inside at night and sweep up all spilled seed to prevent rodent visitors.
A family of Barn Owls can eat 3,000 rodents in a breeding season. An owl box can attract them to your property. Photo by David Goodman

WildCare's Rodenticide Diagnostics and Advocacy Program is a major research initiative in partnership with the Environmental Protection Agency, the Humane Society of the United States, the California Department of Pesticide Regulation, and the UC Davis California Animal Health and Food Safety Laboratory.

Together, we are working to eliminate dangerous rat poisons that affect wildlife, pets and people.

When an animal is admitted to WildCare's Wildlife Hospital, poisoning is not usually the obvious reason for admittance. The majority of our patients are hit by cars, caught by cats, otherwise injured or found without the tell-tale symptoms of rodenticide poisoning such as bleeding from the mouth or other orifices and conspicuous anemia.

But even without symptoms of anti-coagulant rodenticide poisoning, WildCare's data reveals that the majority of rodent-eating patients like hawks, owls, raccoons and foxes are carrying these toxins in their bodies.

And the impact is far-reaching. The various toxins stay in body tissues for a surprisingly long amount of time. Brodifacoum and bromadiolone, two of the most prevalent and toxic second-generation anti-coagulant rodenticides remain in body tissues for 217 days and 248 days respectively, which is one of the reasons so many WildCare patients test positive. These animals are simply unable to rid their bodies of the poisons.

Various studies have found these poisons in the fetuses of pregnant animals, and an increasing number of studies including this one on Notoedric Mange in Bobcats and Mountain Lions show clear links between rodenticide exposure and increased mortality from non-poison-specific causes.

So what do WildCare's data reveal?

The following numbers reflect species totals for WildCare patient rodenticide exposure in 2013:

As the above chart indicates, Barn Owls, Northern Raccoons and Gray Foxes are the animals most affected according to WildCare's data.

Ironically, these three species are particularly adept at eating rodents and thus provide some of nature's best free rodent control. If you have raccoons and foxes moving through your yard, you likely do not have problems with rats and mice.

By allowing these predators to be poisoned, we are destroying the best chance we have at maintaining a natural balance of rodent populations.

The vast majority of tested animals must have received their rodenticide load through secondary poisoning, whereby an animal eating a rat dying of poisoning gets poisoned himself. Due to the nature of so-called "second generation" anticoagulant rodenticides, a rodent may take several days to die of dehydration and internal bleeding, during which time he may return to a bait box again and again.

These rodenticides are advertised to "kill in a single feeding" and, while no doubt the first feeding is what eventually kills the rodent, the time lapse between initial feeding and death means a dramatically higher toxic load builds up in the rodent's body tissues. By the time a Great Horned Owl eats that rodent, it has many times the lethal level of poison in its system.

Other animals in our 2013 testing data including the opossum and the crows probably encountered the poisoned bait itself and consumed enough to poison themselves. Domestic pets may also be poisoned the same way, and data from Poison Control Centers nationwide demonstrate that children can be poisoned too. (Click to read more about risks to children and pets.)

The data WildCare has been collecting on rodenticide prevalence since 2010 provide unequivocal proof that predatory wildlife is being poisoned from eating poisoned rodents. But more information was needed to complete the picture.

How to Control Rodents Humanely

Rodents are an integral part of the environment, and they are the primary food source for most of the predatory animals in our area. It is not possible, nor is it desirable, to eradicate rodents outside.

However, most people do not want rodents inside their homes or damaging their property. The following information will help you effectively eliminate rodent problems without resorting to the use of rat poisons.

Use catch-and-release traps as a safe, sanitary, and humane solution. Catch-and-release traps will allow you to remove rodents from inside your home, but you must prevent their return by sealing entrance and exit holes and removing attractants (see above). Remember it is illegal in the state of California and cruel to relocate animals (click to learn why), so trapped rodents should be deposited outside once entry points have been sealed.

We need your support! Please click here to donate toward our Rodenticide Diagnostics and Advocacy Program!