CAN ORANGUTANS SURVIVE IN AQUATIC ENVIRONMENTS?

As we know, orangutans (Pongo spp.) are arboreal primates. Most of their activities involve navigating the forest canopy using a combination of climbing, clambering, and brachiation.

Given that orangutans share 97% of their DNA with humans, it’s intriguing to explore how their adaptability might extend beyond the treetops, raising the question: Could they also manage to survive in aquatic environments?

Orangutans' Swimming Ability

Orangutans are generally not natural swimmers and tend to avoid water. Both in the wild and in rehabilitation centers, studies and observations consistently show that they steer clear of deep water bodies, rarely being seen swimming.

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According to research published by Bender et al. (2013), hominoids, including humans, are known for their lack of instinctive swimming abilities. Orangutans, in particular, have a notable fear of deep water bodies and generally avoid them in their natural habitats, both in Borneo and Sumatra. This research also indicates that orangutans are primarily observed around shallow water. Despite not demonstrating significant swimming skills, they still possess the potential to swim if necessary.

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Their ecology and adaptations are strongly oriented towards arboreal life, with orangutans frequently relying on a combination of their fore- and hind- limbs for mobility while navigating trees (Thorpe and Crompton, 2008). Additionally, their functional anatomy has evolved to support climbing, bridging, and travelling over flexible branches in the canopy (Zihlman et al., 2011). This has resulted in reduced opportunities for them to interact with water, leading to a diminished innate swimming behaviour. Nevertheless, Bender notes that apes have some ability to cope with negative buoyancy, even though it is limited.

Adaptation to Aquatic Environments

Although orangutans do not have strong swimming abilities, they can adapt to environments with abundant water sources. In some cases, orangutans have been observed using logs or fallen trees to cross rivers or swamps. For example, our Post-Release Monitoring (PRM) team in the Kehje Sewen Forest has recorded the orangutan Sayang and her child, Padma, crossing the Pehpan River multiple times. Another surprising observation is that this resilient mother has also been seen transversing a fallen tree that connected two sides of the river.

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Additionally, orangutans' adaptation to water-rich environments is evident in their foraging behaviour. They are capable of foraging around shallow water and using simple tools to obtain drinking water or find food in the mud. Thus, while they may lack strong swimming abilities, orangutans demonstrate creative problem-solving skills by utilizing tools and materials found in their natural surroundings.

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Research by Russon et al. (2014), shows that rehabilitated orangutans on the pre-release islands of Kaja and Palas, Central Kalimantan, utilize shallow water to forage for small fish and aquatic plants. This research reveals that these rehabilitant orangutans may be obtaining protein not only from insects but also from other aquatic animals. Additionally, they also use twigs or leaves to extract food from the mud or shallow water. These behaviours highlights a substantial level of adaptation among orangutans to water-rich environments.

Can Orangutans Survive in Aquatic Environments?

So, although orangutans are not natural swimmers and tend to avoid deep water, they demonstrate a strong ability to adapt to environments with abundant water sources. They use simple tools and take advantage of shallow water to forage for food and access drinking water. Further studies are needed to fully understand how orangutans adapt to water-rich environments and how these adaptations influence their overall survival.
Reference: 

• Bender, R., & Bender, N. (2013). Brief communication Swimming and diving behaviour in apes (Pan troglodytes and Pongo pygmaeus) First documented report. American Journal of Physical Anthropology, 152(1), 156-162.
• Russon, A. E., Compost, A., Kuncoro, P., & Ferisa, A. (2014). Orangutan fish eating, primate aquatic fauna eating, and their implications for the origins of ancestral hominin fish eating. Journal of Human Evolution, 77, 50-63.
• Thorpe, S., Crompton, R. H., & Wich, S. A. (2008). Orangutan positional behaviour: inter-specific variation and ecological correlates. In Orangutans: ecology, evolution, behaviour and conservation.
• Zihlman, A. L., Mcfarland, R. K., & Underwood, C. E. (2011). Functional anatomy and adaptation of male gorillas (Gorilla gorilla gorilla) with comparison to male orangutans (Pongo pygmaeus). The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 294(11), 1842-1855.