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Another Chipmunk Mystery

Another Chipmunk Mystery

This past week I was in Michigan, where I had an opportunity to get out and do some recording on a couple of mornings.  My earlier posts (1 2) on chipmunk “chuck” calls had stimulated my curiosity in mammal sounds, so when the chipmunks started calling all around me, I turned on the mic — and lo and behold, I got something pretty interesting:

Chipmunk "chuck" call, Peshekee Grade Road, Marquette Co., Michigan, 8/6/2009 (20-43).
Chipmunk "chuck" call, Peshekee Grade Road, Marquette Co., Michigan, 8/6/2009 (20-43).

I was struck by the similarity of this sound to the mystery call from California that was probably made by a Merriam’s Chipmunk.  I can confirm that the Michigan sound came from a chipmunk: after a few minutes of hunting I spotted the little guy on the ground only 10 feet away, twitching his head forward slightly with each call.  Unfortunately, I was under the mistaken impression at the time that only one chipmunk species inhabits the Upper Peninsula of Michigan.  Upon returning home, I discovered that the U.P. actually has two species, Least and Eastern:

Least Chipmunk photoEastern Chipmunk photo
Least Chipmunk (Tamias minimus), Glacier National Park, Montana. Photo by Phil Armitage. Eastern Chipmunk (Tamias striatus), Bas-Saint-Laurent, Quebec. Photo by Gilles Gonthier (Creative Commons 2.0).

If I had been paying attention, I could have identified the little guy to species by looking at his size, shape, and facial striping — but I wasn’t paying attention, so now, alas, I have to use the recording to figure out which ‘munk was chipping.

And there’s the rub.  The vocalizations of Least and Eastern Chipmunks have been described in the literature (e.g., Bergstrom & Hoffman 1991, Burke da Silva et al. 1994), but I can’t find a published spectrogram of this particular sound.  Nonetheless, the evidence points to this being the “chuck” call of Least Chipmunk.  Reasons:

  1. The “chuck” call of Eastern Chipmunk has been well studied, and I’ve heard a couple of recordings of it (e.g., this one), which sound nothing like what I recorded;
  2. The Michigan sound is similar to the probable Merriam’s Chipmunk “chuck” from California, and all western chipmunk species (including Least) are supposed to have similar “chucks,” according to Brand (1976).  Eastern Chipmunk is not closely related to other North American chipmunks.

The Least Chipmunk is the most widespread chipmunk species in North America, occurring throughout much of the Rocky Mountain and Great Basin regions, plus the boreal forest from the Yukon to the U.P. and southwest Quebec. In much of its range it is common, and in many places it is the only chipmunk.  So, those of you who know something about chipmunk vocalizations, this one’s for you: has anyone heard a sound like this from a Least Chipmunk?  How about from an Eastern?  How good is my tentative ID?