Pest Control
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Ultrasonic repellers are small plug-in devices that give off high-pitched sound, above the range of human hearing, which is meant to drive mice away. They are cheap, quiet and need no traps or poison, so it is easy to see the appeal. The evidence that they work is much thinner than the packaging suggests.
How they are supposed to work
Mice hear far higher frequencies than people do. The idea is that a constant or pulsing ultrasonic tone is so unpleasant to them that they leave the area and stay away. Many devices claim to work on rats, insects and spiders as well.
What the research shows
Ultrasonic devices have been tested on rodents for decades, and the findings are consistent. Mice may show a mild aversion when a device is first switched on, but within a few days they get used to it and carry on as before. Where there is food to be had, mice will feed right next to an active device.
Reviews of commercial products have reached the same conclusion: no reliable repellent effect beyond the first few days of use. Claims that the same devices repel insects have fared no better under testing.
Why they fall short in a real house
- The sound does not travel far. High-frequency sound is easily blocked. It does not pass through walls, floors or kitchen units, and soft furnishings absorb it. Mice nesting in a wall cavity, under the floor or in the loft are unlikely to hear it at all.
- Mice get used to it. Any discomfort wears off quickly, especially when the alternative is going without food.
- It treats the symptom, not the cause. Mice come in because there is food and shelter and a gap to get through. A repeller changes none of those.
- Pets may hear it. Some pets, including rabbits, guinea pigs, hamsters and pet rats or mice, can hear ultrasound, and dogs and cats hear higher than we do. A device that does nothing to wild mice may still bother the animals you want to keep.
The main cost of a repeller is often time. While you wait to see if it works, the mice carry on breeding.
What works instead
- Remove the food. Sealed containers, clean surfaces and no pet food left down overnight.
- Trap the mice you have. Snap traps set against walls along their runs are cheap, quick and let you see what you have caught.
- Close the way in. Seal gaps of 6mm and over with wire wool set in mortar, metal mesh or brush strips. Our guide to keeping mice out of your home covers this in detail.
When to call us
If you have tried a repeller and the droppings and scratching have carried on, call us. We find where the mice are living and how they are getting in, clear them with traps or secure bait stations, and proof the entry points. See our mouse control page, or call 01926 632 929.