To operate the Varmint Call, a machined aluminum tube made by King Tool of Bozeman, Mont. ($15; king-tool.com), suck air through the brass mouthpiece. It supposedly imitates the "all-clear" call sounded by gophers and Columbia ground squirrels. Really? In my experience, high-pitched whistles remind ground-dwelling rodents of raptors, and the sound sends them scurrying to their burrows. I decided to test its efficacy over the course of several gopher-shooting sessions last spring.
I established the same pattern: I shot until the easy squirrels were dead and the survivors were wary. Then I sounded the call for varying durations.