The RSPB has found that an ultrasonic cat deterrent significantly reduced the time cats spend in gardens which used them.
This is thought to be the first 'scientific' test of its kind into the efficacy of ultrasonic cat deterrents. The RSPB
measured the effects of the 'CATWatch' (marketed by Concept Research) in 150 gardens over two years. They found that the device reduced the probability of a cat visit by 32% and the total amount of time spent in a garden by cats by 38%. In addition, the effectiveness of the deterrent appeared to increase with time - suggesting that cats learned to avoid gardens that had them.
CatWatch works by detecting movement and body heat within a range of 12m and through an angle of 100 degrees, which triggers an ultrasonic alarm. The sound is not harmful to cats and is not thought to affect other wildlife.