Tarsius sangirensis

Geographic Distribution and Habitat

Sangihe tarsiers are named for their native home on the volcanic island of Sangihe (or Sangir), north of Sulawesi, Indonesia. They naturally thrive in tropical forests, but can also be found in plantations, secondary (or younger) forests, scrub habitats with shorter trees, and near villages. To hunt and live, they typically prefer trees up to 6-10 feet (2-3 m) in height.


In the 1700s Sangihe tarsiers were considered a subspecies of the Spectral tarsier (Tarsius tarsier). During the 1990s and early 2000s, studies revealed that the Sangihe tarsiers are a separate species and monotypic (without any subspecies). Millions of years of isolation may have made them genetically unique compared to other tarsier species with more opportunities to interact and mate.

When first discovered, they were called the “great Sangihe tarsier”. Locally they are called ‘sengkasi’, ‘senggasi’. 

Sangihe tarsier range, IUCN 2023. Range circled in red.

Size, Weight, and Lifespan

Tarsiers are small primates, and even the larger Sahgihe tarsier is only as large as a baseball! They measure only 5.9 inches (15 cm) from the head to the base of their tail. Their thin, scaly trail is about twice as long as their body at 11.6-12.2 inches (29.4 -31 cm). They weigh only 5-5.3 ounces (143-150 g). 

While there is no data on the lifespan of Sangihe tarsiers, some tarsier species have lived to be older than 16 years in captivity and up to 8 years in the wild.


The tarsier’s brown and white camouflage fur, long extremities (fingers, toes, arms, legs, tail), and large eyes are all parts of their anatomy that work to make them perfectly adapted to their nocturnal, predatory, and tree-dwelling (arboreal) lifestyle.

The Sangihe tarsiers have a larger body and skull than other Sulawesi tarsiers. They have tightly packed, short gold fur on their back and white fur on their bellies. Gray fur covers their face, which houses large round eyes with dark pupils surrounded by vibrant orange-brown rings. They have white spots below their ears and black markings outside their nostrils that continue upward to form a point above the nose. All these features give the Sangihe tarsier a cute and almost cuddly appearance but make no mistake, these wild animals are voracious predators with relatively large canines and incisors, perfect for hunting lizards and hard-shelled insects.

Their scaly tails are longer than their body and covered in fine hair. They use their tails to maintain balance during their jumps. Their legs are muscular and make up a large part of their body. Their shin bones (or tibia) are fused and strong. This allows for more muscle attachment in the legs giving them the power to make long-distance jumps. They also have long tarsus (or ankle) bones that inspired the name “tarsiers”, and this feature allows them to extend the reach of their legs as they leap onto a tree. Their hands and feet have long digits and are almost hairless, which helps their grip. Tarsiers have grooming claws (modified nails that curve upward) on their second and third fingers and, in Sangihe tarsiers, these claws are smaller than other species.

Males can be larger and, most times, that is the only visual difference between the sexes. 

Photo: © Phil Chaon/iNaturalist/Creative Commons

Tarsiers are entirely carnivorous (they only feed on other animals and do not eat any plant matter). They are aggressive hunters who opportunistically catch arthropods like beetles, spiders, and even vertebrates such as lizards. Their high protein diet provides tarsiers with enough energy to be active predators and energetic leapers, even though they are one of the smallest primates in the world. 

Behavior and Lifestyle

They are nocturnal, meaning they are active at night and tend to rest during the day. Their large eyes are rich in blood vessels and nerves which help them see in low-light conditions. They take advantage of dark nights to hunt unsuspecting insects and lizards that rest or crawl on trees. They also have specialized spinal bones that help them turn their heads almost 180 degrees in both directions. This means that they can see almost directly behind them while their body is facing the tree trunk. The ability to see almost 360 degrees around you at any time is a great advantage if you are a predator looking for quick prey. It is also handy if you need to keep an eye out for potential flying predators such as owls.

Tarsiers are arboreal and are built for life in the trees. Their powerful leg and arm muscles are almost a quarter of their body weight. These muscles drive their leaps so that they can jump as far as 10 feet (3m), from one tree to another. Tarsiers mostly cling vertically to branches or tree trunks. Their long fingers and toes, almost naked hands and feet give them the grip they need to hold on to the rough bark and clamber up and down trees efficiently. Their large hands are also useful to quickly grab spiders or lizards.

Fun Facts

Sangihe tarsiers are one of the largest tarsiers in Indonesia.

They make sleeping sites in coconut trees, exposed bamboo branches, and vines. 

They are voracious predators who eat insects and lizards. 

They emit unique duet calls between females and males. 

They are one of the most endangered tarsiers in the world. 

Daily Life and Group Dynamics

Tarsiers are truly nocturnal and are rarely out and about before sunset. Once they leave their sleeping sites, they may make duet calls to let others know they are active. This may trigger traveling groups to gather so that they can forage together.  While research on Sangihe tarsier activity patterns is limited, closely related species seem to have a hunting peak early in the night, followed by rest periods, and their level of activity tapers as the night advances into the day.

Sangihe tarsiers travel in groups during the night but may split up to form smaller sleeping groups by the time dawn breaks. These groups use sleeping sites such as coconut trees and vine-covered branches to rest until dusk. Some researchers think that using different sleeping sites may allow the tarsiers to hide more effectively from predators. In addition, their dwindling habitat may force them to split up to find suitable sleeping sites. 


Tarsiers are known for their duet calls which are performed during dusk and dawn, just after they leave their sleeping sites. The Sangihe tarsier duet calls are distinct from the others in their pitch and tone. They are characterized by the females making a two-note call, and the male responding with quick single-note calls. In this duet call, the female’s first note is a long whistle and the second note is a rapidly descending call. The male’s duet call is a series of chirps. They also use calls to maintain contact with each other, especially as they arrive at sleeping spots. These call notes are usually shorter and at the same pitch.

Scent marking is important to tarsiers who need to communicate with each other at night without actually seeing each other. They use urine and scent glands to mark tree trunks and communicate with each other about territorial boundaries and reproductive health. Some of these scent marks can be detected by the human nose and researchers even use the smells to detect, trap, or study tarsiers in the wild.

Reproduction and Family

We do not know much about their specific reproduction and social structures. Some observations indicate that their social structure can be flexible with some individuals forming monogamous pairs (one male and female) while others form polygamous groups of 3-6 tarsiers in a group.

Mating can occur throughout the year with no breeding season. In many mammal species, mothers bear young during spring or summer when there is a maximum amount of food, giving them the best chance of survival.  However, these tarsiers mate throughout the year without a particular season. This is probably because they do not depend on seasonal fruits for energy, and instead, as carnivorous primates, they can maintain a consistent quality of food intake throughout the year even if they switch to different species of insects seasonally.

In general, mating starts when a female enters a peak in hormones during her reproductive cycle (a time referred to as estrus). Female tarsiers use glands near their reproductive organs to deposit scent marks onto a tree trunk or branch. Males then sniff these scent marks to determine how receptive she is to mating. Once both male and female are ready to mate, he mounts or climbs on her back while both cling vertically to a tree. Females are pregnant for 5-6 months (gestation period).

Photo: © Moch. Fadrin A. Indo/iNaturalist/Creative Commons
Ecological Role

Tarsiers are vital to maintaining the ecological balance of the habitat. Insects typically reproduce quickly and are present in a habitat in large numbers. That is a lot of pressure on the plants, which are a common food source for insects. As active nocturnal insectivores, tarsiers have an important ecological function (niche) of controlling the insect population in a habitat, especially as they target insects that are active at night and would normally be missed by daytime predators.

Tarsiers are potential food sources for nocturnal predators such as snakes, owls, civets, and even feral cats in habitats close to human development.

Conservation Status and Threats

The International Union for Conservation of Nature lists the Sangihe tarsier as Endangered (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.

Sangihe tarsiers are one of the most threatened species in the world, appearing in the IUCN’s “2022-2023 Primates in Peril: The World’s 25 Most Endangered Species” publication. Their population is expected to decline further. The limited distribution of the species and the immediate threats of habitat destruction and human encroachment are the biggest threats to the conservation of these tarsiers. 

Singihe Island has an active volcano, Mt. Awu, with about one eruption every 20 years. These eruptions have been deadly, causing dangerous lava flows and ash that destroy the surrounding environment. 

The geological conditions on the island also make it a rich gold deposit that has been mined for years. Local people have protested the presence of the mine for its negative effects on local habitat and biodiversity. However, mining activities have continued and the pressure on maintaining continued forest coverage is a problem. 

Their cute appearance and ease of capture results in many of them being trapped and sold as pets to people in countries within the Southeast Asian region. They are also hunted for bushmeat. 

Conservation Efforts

The Sangihe tarsier is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.

They are protected under Indonesian law, so legally they cannot be hunted or captured. However, it is difficult to enforce this law for such a small animal that can be easily smuggled. 

There are no protected areas or national parks on the island that provide refuge for these primates. The tarsiers are also benefited by some non-governmental and international organizations that conduct research and conservation in the region. To monitor and protect tarsiers and their habitats, conservationists recommend more community-based conservation initiatives.

  • Accessed 20 April, 2024
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Written by Acima Cherian, April 2024