Table of Contents
Advances in Zoology
Volume 2014, Article ID 101763, 8 pages
Research Article

Orangutan Night-Time Long Call Behavior: Sleep Quality Costs Associated with Vocalizations in Captive Pongo

1The Nunn Lab, Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
2Indiana University, E. Kirkwood Avenue 701 Student Building 130, Bloomington, IN 47405-7100, USA
3Indianapolis Zoo, West Washington Street 1200, Indianapolis, IN 46222-0309, USA
4Krasnow Institute at George Mason University, Fairfax, VA 22030, USA

Received 13 June 2014; Revised 28 July 2014; Accepted 11 August 2014; Published 7 September 2014

Academic Editor: Luciano J. Avila

Copyright © 2014 David R. Samson et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Researchers have suggested that the ability of male primates to emit long-distance vocalizations is energetically costly and potentially incurring important adaptive consequences upon the calling individuals. Here, we present the first preliminary data on captive orangutan (Pongo spp.) nocturnal long calls, generated at the Indianapolis Zoo. We used videography to characterize long calls with observed behavioral contexts for 48 nights (816 observed hours totaling 83 long calls). We generated somnographic data for a subset of the long calls. Overall measures of sleep quality generated by infrared videography were then compared to the somnographic, nocturnal long call data. We tested hypotheses related to the proximate mechanisms involved in the initialization of vocalization and the potential costs of emitting long calls to overall sleep quality. We found that (1) performed long calls were conscious and premeditated in nature and (2) greater number of night-time long calls shared a positive relationship with arousability and sleep fragmentation and a negative relationship with total sleep time and sleep quality. These findings strongly suggest that only several minutes of total time invested in long calls throughout the night disproportionately cost the caller by negatively impacting overall sleep quality.