Examining Onset Timing and Duration of Duet Production in Wild White-handed Gibbon (Hylobates lar) Vocalizations — Presentation Detail — Celebration of Scholars

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Examining Onset Timing and Duration of Duet Production in Wild White-handed Gibbon (Hylobates lar) Vocalizations

Name: Rachel Roschi
Major: Biology
Hometown: Oswego, IL
Faculty Sponsor: Angela Dassow
Other Sponsors:
Type of research: Independent research
Funding: University of St Andrews, University of Wisconsin-Madison, and Carthage College

Abstract

White-handed gibbon (Hylobates lar) vocalizations include duets which are used during pair-bonding and defending territorial boundaries. We categorized duets as broad vocalizations which are defined as unsynchronized or non-overlapping calls; or narrow vocalizations which we define as synchronized or overlapping calls.

To explore the function of duets, we elicited vocal responses to the presence/absence of various predator models. Vocalizations were recorded from fifty-two wild gibbons in Khao Yai National Forest in Thailand. Onset duration measurements in minutes:seconds (MM:SS) were taken from the start of the vocalization to the start of two or more individuals calling. Duet duration measurements in minutes:seconds (MM:SS) were taken from the start of multiple individuals calling to the last note of multiple individuals.

Results show that the sitting tiger duets had the shortest average onset timing, though there was no statistically significant difference between predator model responses (p-value = 0.266). The duration of the first duet was found to be statistically significant compared to all later duets for each predator model response (p-value= 0.012). By understanding the onset timing of duets, we can better understand the vocal interactivity of gibbon behavior. Future research will focus on finding the onset duration of duets in captive white-handed gibbon vocalizations and comparing them to the recordings of wild gibbons.