Have you ever noticed how the groundhogs you see on top often end up being the hardest ones to dig to?Now a study in the journal Nature may explain why. It turns out that Richardson's Ground Squirrel uses ultrasonic calls, inaudible to most other ears, to sound the alarm and warn others in the colony that a predator is about. The squirrel's ultrasonic calls, dubbed "whisper calls," are in the 50-kilohertz range-far above the 20 kilohertz that humans can hear.
Not surprisingly, there is also some evidence that other kinds of ground squirrels also make ultrasonic calls, such as marmots. Notes Daniel Blumstein, who studies animal alarm calls at UCLA, "Sometimes (the marmots) open their mouths and they shake their bodies as though they are alarm-calling and nothing comes out."
The groundhog you see on top (and that also sees you) probably has just enough time to scurry down and wall itself off in a latrine pit in a side wall of the burrow.
If anyone is looking for a good science project for their kids, a sure-fire winner is to record the sounds of groundhogs and step down the acoustics to see if they too produce ultrasound alarms. My bet is that they do.
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Sir,
ReplyDeleteyou don't actually need very much complex kit to see if marmots make ultrasonic noise; a cheap heterodyne bat detector kit will do just fine. These units work by producing an electronic signal at the frequency you are interested in, and combining it with the input from the microphone.
This gives you an ultrasonic listening device that you can tune, and the kits for these are most sensitive in the 45 to 55 KHz range, or so I have found. Pipistrelle and Daubenton's bats in the UK echolocate in these ranges, and the bat detectors can hear these bats at ranges of around 20 metres or so.
The other advantage to a bat detector is that it is cheap to build, and cheap to run. Give it a try; the experiment here should be very cheap to do and could be quite useful.