Seattle Life in the Yard

Sustain biodiversity: garden with native plants.

Introduced Poison

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A few weeks ago, I found a dead rat while removing English ivy at Meadowbrook Playfield Park and it had clearly died from internal bleeding. It had eaten the poison bait in one of the many black plastic boxes that have been placed all around the Meadowbrook Community Center and Pool building. When I saw this, I became concerned about the birds and animals that might eat this rat, or part of it, any time after it had eaten the poison, because the secondary poison dose could slowly kill the bird/animal or negatively impact reproduction and survival of offspring.

This NE part of the city still has many big native trees and some small natural areas that are under restoration and because of this, we have a couple bald eagles, coyotes and racoons in our neighborhood and all of them eat rats. The danger for the eagles is that they will scavenge food and eat dead things, like a recently poisoned rat, plus feed them to their chicks. Urban coyotes and racoons eat rats, dead or alive. Parks like Meadowbrook are used as off-leash walking areas for family dogs and the pet owner cannot always see what their dog is doing or even stop them from gobbling down a poisoned rodent.

Just recently my husband and I went to an “Owl Prowl” evening offered by the Seward Park Audubon. It was a very interesting educational evening and we found out that rats can make up a big part of an owl family’s diet. Volume 3 of the “Wild Hope” magazine has an article called “Do No Harm” by Janet McGarry about the Hungry Owl Project (HOP) ( http://www.hungryowl.org/ ). The article is worth a read and the website is worth a visit. One of the quotes from the article is “A family of barn owls in a four-month breeding cycle can eradicate 3,000 rodents.” Wow.

That is way more than five poison boxes can kill in a four-month period. It seems obvious which would be better at rat control – owls! The danger for owls is that they will attack and eat a recently poisoned rodent that hasn’t died and is still moving around while the slow death by internal bleeding is in process which can take several days.

The Forest Stewards who work in the Seattle Parks try to be sensitive to bird and wildlife reproduction so that we don’t inadvertently clear nesting cover and expose this year’s baby birds and critters to predation. The timing for clearing Himalayan blackberry, for example, is for minimizing reproductive harm; we cut canes in the fall and winter when the nesting is over or has not begun, the lack of cane thickets disallows nesting and the roots can be dug up later without concerns for nesting disruption.

I think that we can reduce the harm that is caused by rat poison boxes with a harm reduction approach like replacing poison boxes with boxes that allow mechanical rat traps. These would require more monitoring but maybe that would add a job or two for checking and emptying the traps or with a digital approach, a battery-operated signal would request rat box emptying, similar to a security system notification.

It might be more effective and useful to add owls, owl habitat and owl boxes that would help control rats instead of the steady introduction of poisons into our struggling wildlife food chains and habitats. We might want to encourage and protect other more natural methods of rat control too like existing coyotes and racoons instead of exposing them to secondary poisoning. I would like to see a more effective and less harmful strategy for rat population control than the poison boxes.

Another website weighing in on the issue:  http://www.barnowltrust.org.uk/hazards-solutions/rodenticides/

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