Investigating the Impact of Acoustic Environment and Human Presence on Okapi Faecal Glucocorticoid Metabolites

de Queiroz, MB, Passos, LF ORCID: 0000-0003-4529-9950, de Azevedo, CS, Schork, I, Palme, R, Davies, WJ and Young, RJ (2025) Investigating the Impact of Acoustic Environment and Human Presence on Okapi Faecal Glucocorticoid Metabolites. Noise and Health, 27 (129). pp. 751-759. ISSN 1463-1741

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Abstract

Background: The influence of visitor behaviour and sound pressure levels on zoo animals remains unclear.

Objective: This study examined associations between sound pressure levels, visitor numbers and faecal glucocorticoid metabolites (FGCMs) in a male okapi (Okapia johnstoni) at a UK zoo.

Materials and methods: Data were collected across two 5-day periods representing high- and low-visitor seasons, yielding 10 days of acoustic recordings and matching FGCM samples. Acoustic metrics were calculated for the open and closed periods of the zoo (LeqZ, L10Z and L90Z). Statistical analyses included the Wilcoxon and Welch t-tests, as well as Pearson correlations and multiple linear regression models.

Results:LeqZ and L10Z did not differ between seasons, whereas background noise (L90Z) was higher in the low season (t = –4.42, P = 0.005). Sound levels were generally higher during open hours in both seasons. Correlations between visitor numbers and acoustic metrics were weak and non-significant (high season LeqZ × visitors: r = 0.005, P = 0.994; low season: r = –0.347, P = 0.567). FGCM concentrations did not differ between seasons (72a: P = 1.00; 72T: P = 0.37). Regression analyses showed that LeqZOpen positively predicted 72T FGCMs (β = 5.30 ± 1.85, P = 0.02), while visitor numbers negatively predicted 72T (β = –0.04 ± 0.02, P = 0.04). Visitor numbers did not differ between seasons.

Conclusions: Okapi adrenocortical activity appears more responsive to acoustic conditions than to visitor numbers, suggesting noise as the primary stressor. Reducing noise through enrichment or vegetation may improve okapi welfare.

Item Type:	Article
Uncontrolled Keywords:	1117 Public Health and Health Services; Otorhinolaryngology; 3505 Human resources and industrial relations
Subjects:	Q Science > QL Zoology
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	Ovid Technologies (Wolters Kluwer Health)
Date of acceptance:	1 December 2025
Date of first compliant Open Access:	8 January 2026
Date Deposited:	08 Jan 2026 15:54
Last Modified:	08 Jan 2026 15:54
DOI or ID number:	10.4103/nah.nah_202_25
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27840

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