Earth Notes: The Mouse that . . . Whistles?

Dec 26, 2012

At night, sharp-eared southwestern campers sometimes hear the sound of a fierce predator on the prowl.

It’s an eerie whistle, so high-pitched that it’s right at the edge of human hearing. On a dark night, it just might set the hairs on the back of your neck to tingling.

But have no fear, for what you’re hearing is the cry of the ferocious . . . grasshopper mouse. It’s a small but voracious hunter that without hesitation will kill and eat scorpions and large insects—even other rodents up to three times its size.

Grasshopper Mouse
Credit Utah Division of Wildlife Resources

Grasshopper mice are the size of typical deer mice, but they patrol territories that can be as much as nine times larger. As a result, they’ve developed remarkable ways of communicating with each other. Grasshopper mice bark, howl, and whistle so loudly that they can sometimes be heard at a distance of 200 yards.

In 1931 the great Southwestern mammalogist Vernon Bailey watched one of these 5-inch-long mice stand up on its hind legs, throw back its head, close its eyes, and belt out a prolonged squeaky howl. It was made, he wrote “with raised nose and open mouth in perfect wolf form.”

Once you learn to recognize these distinctive sounds of the desert night you might hear them throughout most of the Southwest. When you do, take a moment to appreciate how evolution has crafted a mouse that howls—and be glad that they don’t come in a much bigger form.

Earth Notes is produced by KNAU and Northern Arizona University’s Sustainable Communities Program.