The dummy with the ultrasound was bitten repeatedly in both set-ups. It was also bitten within the same trial after the ultrasound had been triggered. The average biting duration with the 19 seconds ultrasound was longer (1.39 s) for than for the momentary ultrasounds (1.05 s). Consequently the deterrent effect of the ultrasound is questionable. However, the ultrasound was highly directional, with the sound beam axis along the long axis of the dummy (the ultrasound unit was mounted in the “neck” region of the dummy). At an angle of 30° off the beam axis the sound pressure level is reduced by about 14 dB. Thus the wolves might not have experienced the max level (75 dB re 20µPa rms @ 1m @ 1m) of the ultrasound if coming in from the side of the dummy to bite.