District of North Vancouver will research alternative types of traps and controls for rodents because of the increasing number of owls being killed by secondary rodenticide poisoning.
The district also plans to create a one-year pilot project on alternative rodent control methods at certain facilities. The report is expected to be before council in 2020.
Staff informed council this summer that they received several calls from people who found owls and other raptors dead, later confirmed to have been killed by eating rats infested with poison. Other animals are also dying of secondary poisoning.
“A number of local owls have been confirmed, via toxicity testing, to have ingested fatal amounts of rodenticide. There is additional data that documents the presence of rodenticide occurring in other higher-order predators such as weasels and coyotes as well as scavenger species like birds and squirrels,” the staff said.
DNV says it is now discussing the use of rodenticide and bait traps with its partner organisations, such as the North Vancouver Recreation and Culture Commission, which has a number of facilities adjacent to green belts and wildlife corridors. NVRC currently has a contractor that uses rodenticide bait traps at six sites within the DNV.
The recreation commission has obtained cost estimates for alternative methods.
“Switching to mechanical snap traps or other methodology does add cost due to more labour associated with inspection and maintenance of deployed traps. Rodenticide bait traps have been the preferred rodent control method, mainly due to what was thought to be their effectiveness and lower cost. However more local research on the effectiveness of alternative methods compared to bait traps is needed,” the staff told council.
Staff also conducted an informal survey of a number of local pest control companies and determined that all the companies surveyed used rodenticide bait traps to some degree. Although some companies limit the amount of poisoned bait, none of them appeared to keep track of the amount of rodenticide being deployed into the environment.
Community activist Elise Roberts says DNV should create a new bylaw to end or at least limit the use of second-generation rodenticides in the community. “And that means at any building, community centre, shopping mall, strata,” she says.
Ever since DNV resident Roberts found a dead owl besides Blueridge Creek, she has been actively researching the issue, and has contacted DNV Parks, Health Canada and provincial authorities. She also contacted Sandi Lee, wildlife ecotoxicology technician, at Environment Canada, who told her the agency collected 25 raptor carcasses from North Vancouver between 2013 and 2018.
They were found in Cleveland Park, North and Lower Lonsdale, Central and Upper Lynn, Lower Capilano, Carisbroke and Pemberton Heights.
A post-mortem analysis of 18 carcasses revealed that 10 had detectable liver residues that included rodenticide. Of those 10 samples, eight had total liver residues that suggested a “significant” likelihood of toxicosis. Lee is now working on analysing more recent data from North Shore and Metro Vancouver.
Katharine Fremlin, a doctoral student at the Department of Biological Sciences at SFU, did an ecological risk assessment of pesticide use on owls in DNV, especially potential risks from the recreation centres. She found that owls that eventually died due to injuries or sickness were typically in close proximity to green spaces, public parks or riparian areas.
Many of the owls were within one to two km of recreation and community centers, she said.
“My findings likely underestimated the overall risk of rat poisons to owls on the North Shore as bait boxes with rat poisons are commonly used across North Vancouver at commercial and residential properties – and I only looked at the potential risk from the recreation centers,” she said.
DNV spokesperson Courtenay Rannards said the district was in the process of researching and compiling the findings and would inform the community once the project was complete.