POISON REVIEW
Park board eyes rodenticides after Postmedia revealed that placement of bait boxes around park buildings could result in secondary poisoning of other wildlife
A very sick barred owl in a stream last year near Marine Drive in North Van. Rats that die from rodenticide put out by people can then poison raptors.
The Vancouver park board is conducting a review of rodenticides after Postmedia News revealed that the placement of poisoned-bait boxes around restaurants and other park buildings could result in the secondary poisoning of owls and other wildlife attracted to parks.
“I am totally in favour of looking at options,” Howard Normann, director of park operations, said. “That’s something the park board is going to look at. That’s my strategy moving forward. Where can we avoid those at all cost? It’s great you brought it up. We’ll look at it.”
The review will also determine how many of the boxes are currently out there with active bait and how many are no longer in use but have not been picked up. “It’s also a matter of us doing a better job of monitoring them,” he said, adding they could be placed more discretely.
Rob Hope, raptor care manager at OWL rehab in South Delta, estimated that at least 100 owls brought to the facility last year showed signs of rodenticide poisoning. They were mostly barred owls but also some great-horned owls. Almost all died, and testing is underway to confirm the cause to be rodenticide. A few owls brought in early enough were saved with vitamin K injections.
Hope believes the impact of rodenticide on raptors is getting worse. “People are going for a quick, easy fix,” he said, noting rodenticide bait stations don’t have to be checked as frequently as snap traps.
Metro Vancouver says it does not use rodenticides in regional parks, as a way to reduce secondary poisonings of raptors and other wildlife. Markus Merkens, regional natural resource management specialist, said that where food may attract rodents, such as at concessions, snap traps or electrocution traps are typically used.
“It’s sort of like the electric chair,” he said, noting the pest gets a double zap for good measure.
Elsewhere people use coyote urine, a retail product, to deter rodents, including from chewing on wires. Simon Fraser University is also experimenting with use of sexual pheromones to lure rats into trap boxes.
Postmedia News visited Boundary Bay Regional Park in Tsawwassen and found several black bait boxes around the perimeter of the concession-washroom building at Centennial Beach. The area is a hot-bed for owls that feed on voles and other small prey.
Metro Vancouver spokesman Greg Valou investigated and reported that
the boxes contained snap traps only. “No rodenticide was contained in the boxes. Some of the boxes had the word poison embossed on their plastic, and this led to the confusion about contents. We will recommend that the contractor discontinue the use of these embossed plastic cases for use in regional parks.”
The boxes have been removed. Delta municipality has a few park concessions and no formal policy on the use of rodenticide, but prefers to control the source of the food attracting the rats.
West Vancouver uses snap traps as necessary inside park buildings and the rodenticide Contrac Blox outside. The product claims to be “less toxic to non-target animals, in both primary and secondary poisoning situations, than other single-feeding anticoagulants” but also warns “this product is toxic to fish and wildlife.”
By banning or severely restricting the use of rodenticides, Vancou- ver park board — and its municipal counterparts in the region — could set an example for those using rodenticides on private property, often without knowing the repercussions to wildlife, and domestic dogs and cats.
“It’s a big challenge,” Normann said. “They don’t understand the impact it could potentially have. It’s an education thing. Let’s hope your story brings this to light.”
Biologists with expertise on the effect on rodenticides on wildlife say that at a minimum, bait boxes — especially ones containing the second-generation anticoagulant rodenticides, including bromadialon — should be used strategically and not left out for weeks and months on end.
“Ideally, they wouldn’t be used
in parks,” said Sofi Hindmarch, an independent biologist based in Langley who has extensively researched the issue. “These are our green spaces. This is where a lot of our remaining wildlife is. It’s a contamination of the whole food chain.”
Bait boxes containing rodenticides are widely used in the region, including within residential and business areas, to control rats.
The problem is that rats don’t die inside the boxes where the poison is contained, and can even remove poison to be cached for later consumption, spreading the problem even wider. Instead, the rats continue to roam for days until they die, putting raptors such as greathorned, barred and barn owls at risk of consuming them. Small birds, insects and other animals may also find their way into the boxes to consume the deadly bait. Pets and children can also be at risk.