Thursday, September 6, 2012

Squirrel Facts: Richardson's Ground Squirrels Speak In a "Whisper"

The Richardson's ground squirrel lives on the plains of the northern United States and southern Canada. It is sometimes called the "flickertail" because of its habit of constantly shaking or trembling its short tail. This small (about 7-9 inches long) squirrel has a brown or buff back and tan underside, and remarkably short ears. It can be found both on the prairies and in suburban parks and yards.

Like most ground squirrels, Richardson's ground squirrels live in colonies. However, they are territorial. Closely related females live in proximity to each other and will not tolerate the presence of adult males or unrelated females around their burrows. They have a herbivorous diet, eating primarily leaves, grass seeds, buds, flowers, grains, cereal crops when available, insects, and sometimes carrion. They enter hibernation in July-September, depending on the area. Males emerge from hibernation earliest, in March, with females waking up a couple of weeks later.

When danger is detected, Richardson's ground squirrels, like most squirrels, give alarm calls to warn others of the threat. Recently, scientists have discovered that this species will sometimes give ultrasonic calls, high-pitched "whispers" that are inaudible to humans and many other species but which can be heard by the sensitive ears of other nearby squirrels (thanks to the blog At The Edge Of The Wood for bringing this story to my attention). The researchers in a recent study of ground squirrel communication noticed that sometimes a squirrel would open its mouth and seem to emit a puff of air but no sound, but that other nearby squirrels would rise into a vigilant stance. The researcher then used a bat call detector and found that the squirrels were in fact calling to each other using ultrasonic frequencies.

The advantages of this capability are obvious. The squirrels can alert each other of a predator's presence without being heard by that predator. Besides being undetectable by most species, ultrasonic calls are highly directional, further reducing the chance that they can be heard by unintended recipients. This makes ultrasonic calls extremely useful for sharing rumors about other prairie species.

Hey guys, you didn't hear it from me, but
Thelma the prairie chicken just got implants!

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