Rodenticides continue to affect wildlife in Seattle

by Caroline Guzman

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In a recent study, 125 dead birds of prey, including owls, Cooper’s hawks and red-tailed hawks, tested positive for rodenticides, according to the researchers. the latest report from Urban Raptor Conservancy, a Seattle-based organization of avian scientists. However, many other species are still exposed to these substances and are under-reported.

The adverse effects of anticoagulant rodenticides (ARs) are well known. Although states like Massachusetts, California and New Jersey have moved from ARs to more humane pest control, it remains legal in Washington state.

This unresolved issue has enabled a coalition between Urban Raptor Conservancy (URC), PAWS Wildlife Center, Seattle Audubon, Raptors Are the Solution, Woodland Park Zoo’s Seattle Urban Carnivore Project, and others.

URC took a lead role in opening a case study here in Washington state, and it has been testing birds of prey for several years now. While URC is still waiting for more lab results, Kersti Muul, an independent naturalist and first responder in the city, said: “How much data do we need to change something? Can we start doing something? Because 125 of those raptors is enough to get started.” .”

Muul, also a science teacher for Seattle Audubon, tells a compelling story about a family of owls she followed for more than a decade and discovered that the mother had died as a result of rodenticides. Muul said: “She (mom) died in 2019 and her 2019 chick died in March 2022. So there are actually two of that family that I knew so well. She had no outward trauma. It looked like food had been stolen from her because her claws were bloodied So I had her autopsied and she had three different poisons in her I knew she gave her babies that poison and her partner I was devastated because she died for no reason .” It was this incident that sparked Muul’s interest in the effects of rodenticides on other species, and led her to join the coalition.

Many species of urban wildlife eat poisoned rats, affect their nervous and cognitive skills, degrade their quality of life and drive them to death. The toxins will also affect their offspring, either through nursing or from parents feeding poisoned rats directly to their young.

Some common signs of poisoning in wild animals are walking or flying off balance, shaking their heads repeatedly, an old wound that hasn’t healed, and letting people get close to them, which is highly unusual.

One of the challenges in this ongoing research is that few labs can do this type of testing, and each sample collection costs about $100, according to the URC website† It is expensive and difficult to determine which animal has been affected by ARs before they are sent to the lab.

Nicki Rosenhagen is a wildlife veterinarian at the PAWS Wildlife Center. She contributed to this project for URC by connecting live birds of prey and taking dead ones for poison testing. “There is no way for us to do an easy test on a live bird, because we have to take samples of organs, and we’re not going to do that on live animals. So when we decide to continue treatment, we can only go based on clinical suspicion, clinical signs and history,” she said. “We have to wait until we have enough samples to ship, which can take months, and then we have to we’re waiting for the lab to run the tests and send the information back.” Not only does this delay valuable information, but there isn’t enough funding to make this a more effective or faster process.

Another critical point of discussion is the use of alternative measures to control rats. Some of the alternative solutions that have been discussed include vitamin D overdose (via consumption of cholecalciferol) and bringing to the attention of the public the use of traps and even contraception for rodents. “Finding an alternative, humane solution that is as cheap, convenient and effective as ARs does not currently exist,” Rosenhagen says. “We must all believe that rodent control doesn’t have to be inhumane, and it doesn’t even have to be fatal. In addition, by choosing options that do not contain poison, we eliminate the risk of unintentionally harming other animals.” The challenges in finding solutions to these problems are the reason why these organizations have joined forces.

Ed Deal keeps an eye on birds of prey for URC, of ​​which he is vice president. He says the two poisons that act as a replacement for ARs are bromethalin (a neurotoxin) and cholecalciferol (vitamin D overdose). These poisons don’t build up in the liver like ARs, “but there’s no antidote for bromethalin or cholecalciferol, so if your pet or child eats some, there’s no treatment,” Deal said.

For Rosenhagen, the use of vitamin D is “very inhumane and painful for those animals. Again, poison versus poison is not something I ever recommend.”

Tanea Stephens is the Washington State Coordinator and Director of the Seattle Chapter of RATS. They have been working on a pilot case study finding positive results in rodent contraception. “Poison Free by 2023” is a pilot project in Upper Queen Anne that uses a contraceptive solution for rats called ContraPest, and the pilot study has resulted in a 91% reduction in the original rat population since its implementation in July 2021.

The public also has the power to make a difference. The solution that the PAWS Wildlife Center always offers is ‘exclusion’. According to Rosenhagen, “exclusion” involves removing shrubbery near structures where rats feel comfortable hiding and limiting their food sources. She also mentioned other deadly options, such as traps that are, in theory, instantaneous and don’t pass anything deadly to other animals.

On April 13, a pair of mountain lion kittens died a few days after they were found with three different ARs in their livers, National Park Service officials reported† Rodenticides that affect wildlife are not news. Several cases have been recorded for years about the severity of these poisons in our animals, other than just birds of prey. Fortunately, these organizations continue to work in the best interests of Seattle’s urban wildlife, in the hopes that the public will switch to humane pest control.


Caroline Guzman is an animal and wildlife photojournalist based in Seattle, Washington. She covers stories of animal cruelty, animal laws, conservation, and more. Follow her on Instagram @imcarolineguzman and on Twitter @carolineguzmanor contact her by email at [email protected]

Featured image is attributed to romana klee under a Creative Commons (CC BY-SA 2.0) license

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