Do ultrasonic devices really work against rodents?

DEAR JOAN » I read your article about getting rid of rats and mice and liked your idea of using twine to tie bait to a trap. Have you any information about using ultrasonic devices?

Are they effective, and do you need one per room in a 1,000-square-foot home? How expensive are they, and where can these devices be purchased? — Steven Masui, San Jose

DEAR STEVEN » Researchers say the products are good in theory, but they aren’t effective for a number of reasons.

Though rodents can be irritated by ultrasonic waves, they don’t always immediately vacate your home. They can become acclimated to the waves and after that initial irritation won’t be bothered at all.

Ultrasonic waves at full strength can cause brain damage and even kill, but the devices sold to the public are not that powerful, and the delivery method — through the wiring in your home — is problematic as the waves can be blocked by walls and furniture.

The repellents are marketed as good not only for rodents but also for insects, including ants. As we know, little will stop the Argentine ants that live beneath the Bay Area, and studies done on the devices reveal that they don’t bother the ants at all. About the only insect they did have some marginal success with was crickets.

Having said that, a long time ago my mom and I bought some for our home, and they seemed to work. We got them after one too many ant invasions, and we didn’t have another after installing them. However, after looking at the research that found them ineffective against ants, it might be that my other attempts to get rid of the ants, including placing bait traps around the exterior of the house, were what was working, not the devices.

The research was done several years ago, and the Federal Trade Commission has cracked down on some sellers, so perhaps improvements have been made, making them more of a viable option. They are not horribly expensive — $20 to $40 — unless they don’t work, and then they are way overpriced. You can get them at home improvement stores and through Amazon.

If you decide to give them a try, check the packaging for instructions on how many you’ll need, and be sure to let me know if you have success with them. Readers, have you tried them? I’d love to know how they worked — or didn’t — for you.

Remembering our lost pets

The 15th annual Pet Remembrance Candle Lighting ceremony, sponsored by the Nikki Hospice Foundation for Pets and the Humane Society of the North Bay, is set for 7 p.m. Thursday at Skyview Memorial Lawn Garden Chapel, 200 Rollingwood Drive, Vallejo.

You can bring photos of your pets — deceased or missing — to the chapel starting at 6:30 p.m., where they’ll be added to poster boards. The memorials also will be displayed later at the Humane Society of the North Bay’s headquarters, 1121 Sonoma Blvd., Vallejo.

In addition to the candle lighting and photo display, a video featuring pictures of pets from last year’s ceremony will be played, followed by a reading of names for this year’s memorialized pets.

For more information, call the Nikki Hospice Foundation at 707-557-8595.