Variation in the bark call of the red squirrel (Tamiasciurus hudsonicus)

Calls of the red squirrel (Tamiasciurus hudsonicus; n = 122) were recorded in wild populations from 15 localities in Arizona, New Mexico, Colorado, Ut ah, Wyoming, Montana, Ida-ho, and Washington. Computer-generated audiospect rograms 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 i dentified 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 w ere found among subspecies, within subspecies, and within populations; addi tionally, the southern subspecies utilized a reduced number of bark types. The large number of different bark types and the variation, in bark type us age within populations suggest the potential for communication of such info rmation as individual identification, behavioral states, or gender identifi cation.