Blog Post 2: Proboscis Monkey

 Proboscis Monkey

Nasalis larvatus

Proboscis Monkey walking through his home

Geographic Range 

    The geological range of Proboscis Monkeys is primarily confined to Borneo, where the species in habit regions in Malaysia, Indonesia, and Brunei. "They are not found throughout the island however and are often concentrated in coastal regions. Inland, they are seen along rivers that are scattered throughout the Bornean interior, sometimes over 200 km (124.3 mi), from the coast" (Bennett & Gombek 1993; Meijaard & Nijman 2000a). This range however is due to Proboscis habitat preference, with a need for lowland and proximity to water. 

A map showing Proboscis Monkeys location from https://www.iucnredlist.org/

Habitat Use and Ranging

    Proboscis Monkeys thrive in their coastal environments, particularly within mangrove forests and riverine environments, where they have a variety of food and can evade predators. Proboscis typically utilize lowland environments rarely exceeding 200 meters above sea level require an environment with a consistent water supply (Zach Lussier, 2023). Their reliance on such environments make them dependent on the health of the rivers ecosystem and mangrove forests. Research also suggest that Proboscis Monkeys have an average day range of 900 meters to 2 kilometers which is influenced by the availability of food and the presence of potential threats in their environment. Their home ranges vary depending on the size of their social groups, however their territories often overlap with other groups. This territorial overlap allows them to interact with neighboring groups, communicating through vocals, which ensures shared access to resources such as food and protection.

Locomotion

    The locomotion Proboscis monkeys is a crucial aspect that allows them to adapt to their arboreal lifestyle. They primarily move through the forest canopy by quadrupedal walking and leaping from tree to tree, but they also forage on the ground when necessary. "They move arboreally in the forest canopy by leaping quadrupedally walk from one tree to another tree, and forage in the ground as well."(Arvendi Rachma Jadi et al 2020). Their elongated legs and partially webbed fingers enhance their grip that allows them to grasp trees as they swing through the canopy. What makes Proboscis Monkeys particularly unique is their ability to swim and very often using water as traveling routes and ways to escape danger. Their powerful hind legs allow them to push off with force when leaping between tress and swimming through the water. They are known to dive from trees into rivers, using their webbed feet to propel themselves forward. This versatility in movement from arboreal, terrestrial, and aquatic makes them one of the most adaptable primates in their environment.

   A Proboscis monkey using its powerful legs to jump between trees

Ecology

    Proboscis monkeys play a vital role within their ecosystem as herbivores, primarily consuming leaves while including some fruits and flowers for a fiber rich diet. According to National Geographics "They have complex, chambered stomachs that rely on a host of symbiotic bacteria for digestion". This unique digestive system helps them extract nutrients from their fibrous diets while also reducing competition for food with other primates that relay more on fruits. They are diurnal, meaning they are active during the day, engaging in foraging, social interactions, and resting. Throughout the day they will move between feeding site, interact with their own groups and others from outside, and seek shade near water sources to regulate their body temperature in the hot and humid environment. Their role as primary consumers also aids in the dispersal of seeds, helping the regrowth of their mangrove and riverine habitat.

A Proboscis Monkey eating a leaf

References

Jadi, A. R., Rezeki, A., Dwi, A., Kusindarta, L., & Wijayanto, H. (2020). Locomotion Study of Bekantan (nasalis larvatus). Retrieved from https://www.bio-conferences.org/articles/bioconf/full_html/2020/04/bioconf_icweb2019_04002/bioconf_icweb2019_04002.html#:~:text=They%20move%20arboreally%20in,as%20well.&text=forest%20canopy%20by%20leaping,as%20well.&text=from%20one%20tree%20to,as%20well.&text=tree%2C%20and%20forage%20in,as%20well.

Proboscis monkey, nasalis larvatus - new england primate conservancy. (2024). Retrieved from https://neprimateconservancy.org/proboscis-monkey/#:~:text=Proboscis%20monkeys%2C%20also%20known,its%20banks.&text=island%E2%80%99s%20tropical%20forests%20in,its%20banks.&text=mostly%20on%20the%20coast%2C,its%20banks.&text=greatest%20biodiversity%29%2C%20these%20one%2Dof%2Da%2Dkind,its%20banks.

Proboscis Monkey. (n.d.). Retrieved from https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-proboscis-monkey/#:~:text=Proboscis%20monkeys%20are%20only,Gombek%201993%29.&text=Sebastian%201988%3B%20Brandon%2DJones%20et,Gombek%201993%29.&text=seen%20along%20rivers%20that,Gombek%201993%29.&text=%26%20Nijman%202000a%29.%20They,Gombek%201993%29.

Proboscis Monkey: National Geographic. (n.d.). Retrieved from https://www.nationalgeographic.com/animals/mammals/facts/proboscis-monkey#:~:text=Threats%20to%20Survival