Abstract and Summary
Sound propagation measurements and background noise measurements were conducted to assess the optimal frequency of sounds for long-range vocal communication in thirteenlined ground squirrels (Spermophilus tridecemlineatus). The results show that when the source and receiver are elevated above the ground 18 cm and 6 cm respectively (elevations typically achieved by erect vocalizing and foraging ground squirrels), and the amplitude of the signal matches that produced by ground squirrels, signals 4 kHz to 8 kHz in frequency are optimal for long-range communication. This frequency region matches that of the ground squirrel alarm call. Sound propagation measurements and estimates of sound perception suggest that the effective communicative range of the alarm call is 80–100 m. Demographic data on marked squirrels indicate that over 80 % of known close genetic relatives would reside within the vocal range of alarm calls (Schwagmeyer 1979).