Why the research is clear
The idea behind ultrasonic repellers is that high-frequency sound (above 20 kHz, inaudible to most humans) causes distress in rodents and deters them from the area. This is a theoretically plausible premise — rodents use ultrasonic communication and are sensitive to high-frequency sounds. The problem is habituation. Rodents habituate to non-threatening stimuli within days, including ultrasonic frequencies. Numerous peer-reviewed studies (University of Nebraska, 1994; Kansas State University, 2003; several subsequent replications) placed rodents in environments with and without ultrasonic devices and measured activity. The result was consistent: rodents showed brief initial avoidance (1-3 days) followed by return to normal activity, indistinguishable from no device at all. Even studies funded by the device manufacturers failed to show sustained effect.
Health Canada reviewed ultrasonic pest-control devices and does not register them as pest-control products because they cannot demonstrate efficacy under the Pest Control Products Act standard. They are instead sold as consumer electronic devices, which have no efficacy requirement. This is why you see them at Canadian Tire and Walmart without a pesticide registration number — because they're legally not claiming to be a pesticide.
What we see on real Metro Van inspections
When we arrive at a rodent callout and find ultrasonic devices running, the scenario is almost always the same: the homeowner installed the devices 2-4 months ago after seeing the first mouse, activity seemed to slow for a week or two (consistent with the brief initial avoidance effect, or simply reflecting normal population fluctuation), then activity returned. By the time they called us, they have droppings in multiple rooms and often can hear sounds in the walls. The devices are typically right next to the heaviest activity sites — rodents nest within 2 metres of the device because the ultrasonic field is directional and very limited in range, leaving dead zones behind furniture and appliances where rodents spend most of their time.
Other rodent-control myths in BC
- Peppermint oil: provides brief scent disturbance at best. Mice habituate within days. At the concentrations required to have any sustained effect (cotton balls soaked in undiluted peppermint oil, replaced every 2 days), the cost exceeds snap traps and the efficacy doesn't.
- Mothballs indoors: illegal for this use under BC's Integrated Pest Management Act. Naphthalene and paradichlorobenzene mothball products are registered as closet/storage moth deterrents, not rodent repellents. Using them as rodent deterrents violates their label, which is illegal under the Pest Control Products Act.
- Indoor cats as mouse control: a single indoor cat can intercept individual mice but cannot eliminate an established colony. Mice nesting inside walls, attics, and crawlspaces are inaccessible to a cat. Cats are not a substitute for structural exclusion.
- Fox urine or predator scent sprays: field tests show initial avoidance of 1-3 days followed by habituation. No sustained effect on established populations. Also needs to be refreshed after rain, which in Metro Vancouver means near-daily application.
- Bay leaves in pantry: a folk remedy with no rodent-deterrent evidence in controlled settings.
What actually works
The evidence-based tools are the same ones they've been for 50 years: snap traps (Victor, T-Rex), tamper-resistant bait stations with first-generation anticoagulant bait (post-2023 SGAR ban), electronic traps (Goodnature, Victor electric) for snap-trap-averse homeowners, and structural exclusion. None of these are exciting consumer products. None of them are sold on Amazon Prime for $40. All of them have documented efficacy in peer-reviewed literature and thousands of actual Metro Vancouver infestations. See our [rodent control method comparison](/guide/rat-baiting-stations-vs-snap-traps-bc) for the full breakdown.