Effect of Noise on Bornean Orangutans’ Glucocorticoid Metabolite (GCM) Levels

Title (eng)
Effect of Noise on Bornean Orangutans’ Glucocorticoid Metabolite (GCM) Levels
Author
Marina Bonde de Queiroz
Author
Luiza Figueiredo Passos
Author
Cristiano Schetini de Azevedo
Author
Ivana Schork
Author
Rupert Palme
Author
William J. Davies
Author
Robert John Young
Abstract (eng)
Zoos are increasingly hosting out-of-hours events such as ‘Music Nights’ to increase visitation, raising potential animal welfare concerns due to anthropogenic noise pollution. This study examined the physiological stress response, measured through faecal glucocorticoid metabolite (FGCM), of Bornean orangutans (Pongo pygmaeus; n = 6) at Twycross Zoo during four consecutive weekends of live music events. Faecal samples were collected over these weekends and compared with a comprehensive 24 h acoustic analysis of the enclosure. The acoustic data indicated that the environment was dominated by noise from the ventilation system, which masked the sound from the live music. Comparisons of acoustic metrics between Event and Non-Event periods showed that LAeq, LA10, and LA90 were significantly higher during event hours or open zoo periods. In contrast, daily means did not differ. Group-averaged FGCM concentrations were higher on Event days (mean ± SE: Event = 826 ± 99 ng/g; No Event = 701 ± 44 ng/g), but comparisons for each individual showed no significant differences (Batu: t = 0.577, p = 0.596; Maliku: t = 1.475, p = 0.212; Molly: t = 0.290, p = 0.786; Kibriah: t = 0.771, p = 0.506). In contrast, FGCM concentrations increased significantly with increasing acoustic levels (LAeq) across individuals, with Batu and Maliku generally showing higher FGCM levels in response to louder days. These findings suggest that the constant background noise may have caused partial habituation. At the same time, individual variation highlights the importance of assessing physiological responses at the individual level, as relying on group-level data may overlook adverse welfare effects on sensitive individuals.
Keywords (eng)
SoundscapeStressOrangutanZoo
Type (eng)
journal article
Language
[eng]
Persistent identifier
https://phaidra.vetmeduni.ac.at/o:5095
DOI
10.3390/ani15233384
Is in series
Title (eng)
Animals
Volume
15
Issue
23
ISSN
2076-2615
Issued
2025
Number of pages
17
Publication
MDPI
Version type (eng)
version of record (published version)
Date issued
2025
Access rights (eng)
open access
License
CC BY 4.0 International
Rights statement (eng)
© 2025 by the authors