Well look, you might think I'm unashamedly biased here - well of course I am! But let's look at the evidence and feedback on these devices and see how well they work.
Electronic deer scarers, which include ultrasonic devices, motion-activated lights, sounds, sprinklers, or electric shock systems, have mixed effectiveness in deterring deer, with results varying by type, deer population pressure, and environmental factors. Overall, they are not considered reliable long-term solutions, as deer often habituate to them over time, but some types can provide short-term relief or work better when combined with other methods like repellents or fencing.
Ultrasonic scarers, which emit high-frequency sounds inaudible to most humans, are among the least effective for deer. This is just a warm and fuzzy way to say they are virtually useless, and a potential health hazard to humans as well.
Research and expert opinions indicate they rarely provide lasting deterrence, with deer quickly adapting or ignoring the sounds, especially in high-pressure areas. User experiences and tests, such as those on animals like squirrels or dogs, show variable reactions, but specific deer trials often conclude they're ineffective.
Promotional claims suggest they work against deer and other pests (oh really?), but independent reviews are skeptical. Overall, scientific consensus leans toward ultrasonic repellers being ineffective for deer long-term. They may provide short-term deterrence when novel, but deer adapt, especially in high-pressure areas with food scarcity. Some studies note potential human health effects, like discomfort or headaches from prolonged exposure to high frequencies, particularly for younger people or those with sensitivity.
Motion-activated scarers, such as sprinklers or lights that trigger upon detecting movement, tend to perform better initially by startling deer with water, noise, or illumination. These can reduce damage short-term, especially if repositioned frequently to prevent habituation, but effectiveness wanes over weeks or months.
Sure, I would admit that something that makes a sudden noise, or sprays out water could be good, but consider how these things have to be set up in the garden.
1. How is power and water supplied to the device to spray water. A solar powered device to pump water would need alot of battery storage to handle the load, or to light-up the device? Costs would be a big issue and render many impractical.
2. If it's located in the garden then it should be ok to get a hose clipped in, but otherwise in more remote areas this is not practical, nor possible to get a power supply to that device.
Motion-activated devices generally perform better than non-motion ones because the element of surprise prevents quick habituation. However, studies and reviews show variable results, often effective short-term (1-6 weeks) but waning as deer learn to ignore them, especially if food is scarce. These devices work, but powering them to do a decent spray or make a noise is a problem, unless mains power is supplied.
The BEST solution is to combine the above with a topically sprayed protein or fat repellent, especially where the device battery is limited. This double-banger approach spreads the risk and enhances effectiveness. Numerous studies prove that a topical spray is the best way to go, and that is the approach exclusively adopted by commercial forestry applications.
If deer are your primary pest then FATBANG is the solution!
If a mix of deer and rabbits are the problem then go for BANGBANG!