Importance of feeding branches to gorillas under human care

Misako Namiki; Misako Namiki

doi:10.3934/aas.2025004

AIMS Animal Science

2025, Volume 1, Issue 1: 39-50. doi: 10.3934/aas.2025004

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Case Report

Importance of feeding branches to gorillas under human care

Misako Namiki ^,

Teikyo University of Science, 2525 Yatsusawa, Uenohara, Yamanashi Prefecture, Japan

Received: 14 February 2025 Revised: 08 July 2025 Accepted: 31 July 2025 Published: 25 August 2025

In this study, we investigated the holding duration of various food types consumed by gorillas in captivity, focusing on the dominance of branches among the provided food items. In the welfare practices of gorillas under human care, extending the time spent on feeding activities was emphasized by referencing time budgets observed in the wild. Additionally, from a nutritional perspective, the provision of leaves and bark was prioritized. In this investigation, the duration from grasping with the hand, performing various manipulations, placing the item in the mouth, to releasing was defined as "holding duration", which was compared between branches and other food types supplied simultaneously at the same enclosure. The study was conducted between 2017 and 2018 at Tokyo's Ueno Zoological Garden, in Japan, involving five gorillas kept in the same enclosure. Data from a total observation time of 63 hours across 17 survey days were analyzed. Additionally, a young female was observed modifying a twig to retrieve food that had fallen into a crevice in the rock. The author analyzed the relationship between food types and individual variations in holding duration using a non-parametric two-factor analysis and conducted comparisons across different branch types using t-tests. As a result, the holding duration for branches was significantly longer than that for vegetables across all individuals, and no interaction between individuals and food types was observed.
- branch and leaves,
- enrichment,
- foraging,
- holding duration,
- tool use behavior
Citation: Misako Namiki. Importance of feeding branches to gorillas under human care[J]. AIMS Animal Science, 2025, 1(1): 39-50. doi: 10.3934/aas.2025004

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Abstract

In this study, we investigated the holding duration of various food types consumed by gorillas in captivity, focusing on the dominance of branches among the provided food items. In the welfare practices of gorillas under human care, extending the time spent on feeding activities was emphasized by referencing time budgets observed in the wild. Additionally, from a nutritional perspective, the provision of leaves and bark was prioritized. In this investigation, the duration from grasping with the hand, performing various manipulations, placing the item in the mouth, to releasing was defined as "holding duration", which was compared between branches and other food types supplied simultaneously at the same enclosure. The study was conducted between 2017 and 2018 at Tokyo's Ueno Zoological Garden, in Japan, involving five gorillas kept in the same enclosure. Data from a total observation time of 63 hours across 17 survey days were analyzed. Additionally, a young female was observed modifying a twig to retrieve food that had fallen into a crevice in the rock. The author analyzed the relationship between food types and individual variations in holding duration using a non-parametric two-factor analysis and conducted comparisons across different branch types using t-tests. As a result, the holding duration for branches was significantly longer than that for vegetables across all individuals, and no interaction between individuals and food types was observed.

References

[1]	Brambell FWR (1965) Report of the Technical Committee. Animals kept under intensive livestock husbandry systems. HM stationery office.
[2]	Mellor DJ (2016) Updating animal welfare thinking: moving beyond the "five freedoms" towards "A life worth living". Animals (Basel) 14: 21. https://doi.org/10.3390/ani6030021 doi: 10.3390/ani6030021
[3]	Shepherdson DJ (1998) Tracing the path of environmental enrichment in zoos. In: Second Nature - Environmental Enrichment for Captive Animals (Shepherdson, D., Mellen, J. D., Hutchins, M. eds), Smithsonian Institution Press, Washington, DC, 1–13.
[4]	Hosey G, Melfi V, Pankhurst S (2013) Zoo animals: behaviour, management, and welfare, Oxford University Press. https://doi.org/10.1093/hesc/9780199693528.001.0001
[5]	Veasey JS, Waran NK, Young RJ (1996) On comparing the behaviour of zoo housed animals with wild conspecifics as a welfare indicator. Anim Welf 5: 13–24. https://doi.org/10.1017/S0962728600018297 doi: 10.1017/S0962728600018297
[6]	Lutz CK, Novak MA (2005) Environmental enrichment for nonhuman primates: Theory and application. ILAR J 46:178–191. https://doi.org/10.1093/ilar.46.2.178 doi: 10.1093/ilar.46.2.178
[7]	Robira B, Benhamou S, Obeki BE, et al. (2023) How do primates decide where to feed? Insights from wild western gorillas. Anim Behav 204: 25–36. https://doi.org/10.1016/j.anbehav.2023.07.012 doi: 10.1016/j.anbehav.2023.07.012
[8]	Fuh T (2013) Western lowland gorilla (Gorilla gorilla gorilla) diet and activity budgets: Effects of group size, age class and food availability in the Dzanga-Ndoki National Park, Central African Republic.
[9]	Maple TL, Perdue BM (2013) Defining animal welfare. In: Zoo animal welfare. Berlin, Heidelberg: Springer Berlin Heidelberg, 21–33. https://doi.org/10.1007/978-3-642-35955-2_2
[10]	Smith BK, Remis MJ, Dierenfeld ES (2020) Impacts of dietary modifications on the behaviour of captive western lowland gorillas (Gorilla gorilla gorilla). J Zoo Aquar Res 8: 50–58.
[11]	Richardson S (2024) Primate enrichment categories: A literature review of current trends. Anim Behav Cogn 11: 87–110. https://doi.org/10.26451/abc.11.01.06.2024 doi: 10.26451/abc.11.01.06.2024
[12]	Ramont M, Principe N, Prostko R, et al. (2025) The provision of browse and its impacts on the health and welfare of animals at the zoo: A review. Zoo Biol 44: 105–125. https://doi.org/10.1002/zoo.21883 doi: 10.1002/zoo.21883
[13]	TAG AA (2016) AZA Gorilla species survival Plan® program. Available from: https://www.aza.org/species-survival-plan-programs
[14]	Abelló MT, Rietkerk F, Bemment N, et al. (2017) EAZA best practice guidelines. Available from: https://strapi.eaza.net/uploads/202406_EAZA_Western_lowland_gorilla_Best_Practice_Guidelines_3rd_edition_V2_954baec722.pdf
[15]	Cheang A (2020) Activity budget and spatial location of captive Western lowland gorillas (Gorilla gorilla). J Biol Sci 2020: 4–13.
[16]	Albrecht A, Behringer V, Zierau O, et al. (2024) Dental findings in wild great apes from macerated skull analysis. Am J Primatol 86: e23581. https://doi.org/10.1002/ajp.23581 doi: 10.1002/ajp.23581
[17]	Namiki M, Kobayashi T (2024) Significance of branches and leaves as feed components for captive Western lowland gorillas. J Vet Sci Med Diagn 13: 1–3. https://doi.org/10.54615/2231-7805.1000109 doi: 10.54615/2231-7805.1000109
[18]	Breuer T, Ndoundou-Hockemba M, Fishlock V (2005) First observation of tool use in wild gorillas. Plos Biol 3: e380. https://doi.org/10.1371/journal.pbio.0030380 doi: 10.1371/journal.pbio.0030380
[19]	Prieur J, Pika S (2020) Gorillas' (Gorilla g. gorilla) knowledge of conspecifics' affordances: Intraspecific social tool use for food acquisition. Primates 61: 583–591. https://doi.org/10.1007/s10329-020-00805-6
[20]	Vančatová M, Vančata V (2021) The simple objects place in enclosure for gorillas initiate rare or new behavioural patterns–implications for the origin of hominine tool behaviour. Anthropologie (Brno) 59: 45–54. https://doi.org/10.26720/anthro.20.01.17.1 doi: 10.26720/anthro.20.01.17.1
[21]	Nakamichi M (1999) Spontaneous use of sticks as tools by captive gorillas (Gorilla gorilla gorilla). Primates 40: 487–498. https://doi.org/10.1007/BF02557584 doi: 10.1007/BF02557584
[22]	Fens A, Clauss M (2024) Nutrition as an integral part of behavioural management of zoo animals. J Zoo Aquar Res 12: 196–204.
[23]	Davison S, Mascellani BA, Ward Z, et al. (2025) Cardiometabolic disease risk in gorillas is associated with altered gut microbial metabolism. NPJ Biofilms Microb 11: 33. https://doi.org/10.1038/s41522-025-00664-3 doi: 10.1038/s41522-025-00664-3
[24]	Fuller G, Murray A, Thueme M, et al. (2018) Behavioral and hormonal responses to the availability of forage material in western lowland gorillas (Gorilla gorilla gorilla). Zoo Biol 37: 23–34. https://doi.org/10.1002/zoo.21393 doi: 10.1002/zoo.21393
[25]	Jones CE (2021) Socio-and cognitive ecology of zoologically-housed western lowland gorillas (Gorilla gorilla Gorilla): Spacing and behavior as a function of resource distribution. University of Georgia.
[26]	Nsekanabo JD, Leeds A, Eckardt W, et al. (2022) Distinguishing mobility and immobility when establishing species-specific activity budgets: A case study with gorillas (Gorilla berengei berengei and Gorilla gorilla gorilla). Zoo Biol 41: 503–511. https://doi.org/10.1002/zoo.21673 doi: 10.1002/zoo.21673
[27]	Pinillos RG, Appleby MC, Manteca X, et al. (2016) One Welfare - a platform for improving human and animal welfare. Vet Rec 179: 412–413. https://doi.org/10.1136/vr.i5470 doi: 10.1136/vr.i5470

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