Calls of the red squirrel (Tamiasciurus hudsonicus; n = 122) were recorded in wild populations from 15 localities in Arizona, New Mexico, Colorado, Utah, Wyoming, Montana, Idaho, and Washington. Computer-generated audiospectrograms of 20- or 30-second samples from a calling bout of each individual were analyzed. Eighteen bark types (distinct forms of the bark call) were identified plus a 19th category that included rarely used, longer bark calls. The frequency of use of each bark type within the sample was recorded for each squirrel. Differences in frequency of use of the various bark types were found among subspecies, within subspecies, and within populations; additionally, the southern subspecies utilized a reduced number of bark types. The large number of different bark types and the variation in bark type usage within populations suggest the potential for communication of such information as individual identification, behavioral states, or gender identification.
Yamamoto, Osamu; Moore, Barry; and Brand, Leonard
"Variation in the bark call of the red squirrel (Tamiasciurus hudsonicus),"
Western North American Naturalist: Vol. 61
, Article 2.
Available at: http://scholarsarchive.byu.edu/wnan/vol61/iss4/2