The province of B.C. has instituted a temporary ban, effective immediately, on the "widespread sale and use" of so-called second-generation rat and mouse poisons.
The announcement of the ban came in a July 21 news release from the Ministry of Environment and Climate Change Strategy that said the prohibition would last 18 months.
In the release, secondary poisonings of wildlife such as owls were cited as the reason for the ban. The year-and-a-half moratorium on second-generation anticoagulent rodenticides (SGARS) will give the government time, according to the release, to conduct a "science review" and promote alternatives to the powerful poisons via a Rodenticide Action Plan.
"The ministry’s Rodenticide Action Plan also includes increased public information activities to raise awareness of the risks of SGARS, the benefits of alternatives, and the promotion of the integrated pest management system to reduce unnecessary pesticide use," the bulletin noted.
Secondary poisonings occur when rodents, mostly rats and mice, consume a lethal or sublethal doses of poison and are then caught and eaten by predators such as owls, hawks, crows, coyotes, or pets like cats or dogs. Poisoned rodents are often easier to catch by such predators because of slowed movements or failure to adequately conceal themselves.
However, it was unclear from the announcement how effective the temporary rodenticide ban would be in curbing secondary poisonings. Extensive use will still be permitted in certain sectors: "Exemptions to the temporary ban include when use supports agricultural production and food safety," the release said. "Health services, such as hospitals, food processing and storage facilities, restaurants, and grocery stores, are also exempt."
“We share the concerns of many British Columbians that rodenticide use is harming, and too often killing, birds, pets and other wildlife,” Minister of Environment George Heyman said in the release. “That is why we are taking action to reduce risks, conduct a review and step up our efforts to reduce unnecessary pesticide use, rather than safer alternatives.”
Most "first generation" anticoagulent poisons cause death gradually, sometimes after rodents have consumed multiple baits, with death usually coming days after an initial dose. The poisons work by disrupting the production of blood-clotting factors and causing internal bleeding, with death resulting from hemorrhagic shock and/or anemia.
Second-generation anticoagulents are much more toxic, usually lethal after one dose.
Federally, Health Canada’s Pest Management Regulatory Authority decides, after evaluating risks, what pesticides can be sold. B.C.'s Integrated Pest Management Act is administered through the Ministry of Environment.
According to a posted response to the ban announcement by the B.C. Society for the Prevention of Cruelty to Animals (BC SPCA), the prohibition is good news for wild animals: "This is a huge win for local wildlife—as more humane alternatives to control rodents will mean less poison in the environment to potentially consume for owls, hawks, coyotes, and many more species up the food chain."
The BC SPCA page noted that 16 B.C. municipalities had passed bylaws or motions since 2020 banning rodenticide use on municipal properties, including New Westminster, Victoria, Esquimalt, West Vancouver, Salmon Arm, the City of North Vancouver, Port Moody, Sooke, Saanich, and the District of North Vancouver.
In the Environment Ministry release, Deanna Pfeifer, a spokesperson for the Rodenticide Free B.C. campaign, said that alternative methods of pest control are better than poisons for several reasons.
“Thousands of British Columbians have voiced their concerns over the use of rodenticides and the harmful impacts they have on owls and other animals,” Pfeifer said. “I am pleased to know the minister is acknowledging the detrimental effects rodenticides can have on our ecosystem and look forward to an increased awareness of alternative pest management approaches that are safer, more humane and more effective in the long term."
The BarnOwlsBC website, which describes itself as "a resource site for barn owl conservation", says that the injurious effects of rodenticide exposure in B.C. wildlife has been known for decades.
"Every year in B.C. there are several documented cases of raptors such as owls and hawks that have died as a result of eating rodenticide exposed rodents," the site says. "Secondary rodenticide poisoning of raptors is not a new phenomenon in B.C. Residue data dating back from the early 90s. when monitoring first began. documented exposure in all the resident owl species (barn owl, great-horned owl, and barred owl). Since then, the residue data collected annually in B.C. is showing that the number of raptors species exposed, the proportion of the population being affected by anticoagulant rodenticides, and the overall concentration in individual raptors is increasing."
Information on the BarnOwlsBC site indicates that a single owl can kill up to 1,000 rodents per year.
A 2014 study prepared for the Ministry of Environment showed the extent to which second-generation anticoagulents had been discovered in owl carcasses in the province.
"Anticoagulant rodenticides are commonly used to suppress rodent populations, and subsequent direct or secondary poisoning of non-target species has been documented worldwide...In B.C., work by Albert et al. (2010) found that 62%...of the Barn Owl carcasses collected throughout the province, between 1988 and 2003, tested positive for one or more anticoagulant rodenticide. In most instances, Barn Owls were testing positive for second-generation anticoagulant rodenticides. These compounds are found to be more toxic and persistent in the tissues of animals, thus posing a greater risk to nontarget species than the more commonly known first-generation products such as warfarin."