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

Queiroz, MBD ORCID: 0000-0003-0153-586X, Passos, LF ORCID: 0000-0003-4529-9950, Azevedo, CSD ORCID: 0000-0003-0256-9017, Schork, I, Palme, R ORCID: 0000-0001-9466-3662, Davies, WJ and Young, RJ ORCID: 0000-0002-8407-2348 (2025) Effect of Noise on Bornean Orangutans’ Glucocorticoid Metabolite (GCM) Levels. Animals, 15 (23). p. 3384. ISSN 2076-2615

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Abstract

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.

Item Type:	Article
Uncontrolled Keywords:	0502 Environmental Science and Management; 0608 Zoology; 0702 Animal Production; 3003 Animal production; 3009 Veterinary sciences; 3109 Zoology
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences Q Science > QL Zoology S Agriculture > SF Animal culture
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	MDPI
Date of acceptance:	21 November 2025
Date of first compliant Open Access:	27 November 2025
Date Deposited:	27 Nov 2025 16:34
Last Modified:	27 Nov 2025 16:34
DOI or ID number:	10.3390/ani15233384
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27636

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