Interestingly, in the course of his research Lawhern tested the whistles in the presence of seven species of the deer family, including 45 white-tailed deer. Possible responses he looked for included ears or head turning, flinching, or looking in the direction of the sound. Out of all these animals, however, only one response was noted, this from a single bull elk. At the shrill sound of the lower pitched whistle (audible to human ears) he charged the enclosing fence, in the process breaking a 2X4 post. In prolonged rage, he then bugled and urinated.