The Vocal Range of Alarm Calls in Thirteen-lined Ground Squirrels

Authors

  • C. H. Brown,

    Corresponding author
    1. Department of Psychology, University of Missouri, Columbia
    2. Department of Psychology, University of Oklahoma, Norman
      Department of Psychology, University of Missouri, Columbia, MO 65211, U.S.A.
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  • P. L. Schwagmeyer

    Corresponding author
    1. Department of Psychology, University of Missouri, Columbia
    2. Department of Psychology, University of Oklahoma, Norman
      Department of Psychology, University of Oklahoma, Norman, OK 73019, U.S.A.
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Department of Psychology, University of Missouri, Columbia, MO 65211, U.S.A.

Department of Psychology, University of Oklahoma, Norman, OK 73019, U.S.A.

Abstract

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).

Zusammenfassung

Laut-Reichweite und Hintergrundgeräusche wurden gemessen, um die optimale Frequenz für vokale Kommunikation über größere Entfernung beim Erdhörnchen Spermophilus tridecemlineatus zu bestimmen. Befindet sich die Schallquelle 18 cm über dem Boden (wie typischerweise beim rufenden Hörnchen) und der Empfänger 6 cm über dem Boden (wie typischerweise beim futtersuchenden Hörnchen), dann reicht ein Signal von der Amplitude eines Erdhörnchen-Warnrufes am weitesten, wenn es zwischen 4 und 8 kHz liegt. In diesem Bereich liegen die Warnrufe, und sie sind, gemessen an der Beantwortung, 80–100 m weit hörbar. Demographische Daten von markierten Hörnchen zeigen, daß über 80 % der genetisch verwandten und einander bekannten Hörnchen innerhalb der Stimmreichweite des Warnrufes wohnen (Schwagmeyer 1979).

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