North Cowichan has decided to ban the use of anticoagulant rodenticides to deal with rodents in all properties owned by the municipality.
But council made it clear at its meeting on May 19 that North Cowichan does not have the jurisdiction to ban the use of anticoagulant rodenticides broadly across the municipality, and can only do so on properties owned by North Cowichan.
Residents in North Cowichan can expect to hear more about the harmful impacts of anticoagulant rodenticides (which work by interfering with the activation of vitamin K, a critical component in the production of blood clotting factors in the liver) through upcoming communications from the municipality, and the sharing of educational materials.
A report by Dave Preikshot, North Cowichan’s senior environmental specialist, said there is a body of evidence suggesting that ACRs can be consumed by non-target species.
In particular, raptor species like eagles, owls, and hawks are highly susceptible to ACR poisoning when rodents are a primary diet item.
“Several local media reports have described an increasing incidence of ACR poisoned owls arriving at animal rehabilitation facilities,” Preikshot said.
“The absolute effect of any concentration of ACR in a given raptor species is very difficult to assess. Still, the opinion of [studies on the issue] is that ACRs have a significant and negative effect on raptor populations.”
Preikshot said there is also a potential risk posed to other wildlife, domestic animals, and human health through the continued use of ACRs.
He said most reputable sources recommend that as the first line of defence, all buildings and storage infrastructure should be modified to discourage entrance by rats and other rodents, including blocking all openings with durable materials, or using heavy wire mesh to cover openings that cannot be blocked, and removing or securely isolating any sources of food and water.
But Preikshot said that, despite these measures, rats and rodents continue to access a number of municipal buildings and property in North Cowichan.
He said other available methods of rodent control include blunt-force traps and euthanizing live captures.
“‘Snap’ traps are not regarded as effective for institutional use by pest-control operators,” Preikshot said.
“Because rats live communally, they will quickly learn to avoid snap traps when observing other rodents caught by these traps. Multiple-kill repeater traps are regarded as more effective but are also significantly more expensive to purchase and maintain than snap traps or rodenticide.”
Preikshot said live traps are also an option for managing rodent populations on municipal property.
“However, the most significant consideration in the use of live traps is that they require either euthanizing the rodent by hand or releasing it,” he said.
“It’s not permissible to freeze, drown, electrocute, or asphyxiate any mammal pests. Because many rodents are invasive, releasing them to the wild would likely have a negative effect on the environment through competition with native rodents. A likelier outcome of releasing rodents to the wild is that they will simply locate a new home on nearby residential, commercial or agricultural property.”
Preikshot said an estimate for changes to costs for rodent control was prepared by the contractor currently engaged in managing rats and other pests at a number of North Cowichan properties.
“The current labour and maintenance cost for rodent control at these sites is approximately $7,000 per year,” he said.
“It’s anticipated that the added expenses of maintaining blunt-force or live traps would increase the annual cost of rodent control to about $14,000 per year.”