Makassar tarsier, Tarsius fuscus
MAKASSAR TARSIER
Tarsius fuscus
Geographic Distribution and Habitat
The Makassar tarsier population is restricted to the southwestern peninsula of Sulawesi island, near Makassar city. They prefer dense canopy forests with dark and humid conditions but are also highly adaptable to different forest types with varying food sources. Makassar tarsiers are often seen in gardens. They occupy the lower parts of the forest canopy, about 3 to 6 feet ( 1-2 m) from the ground.
Tarsiers are notoriously difficult to identify based on their coat color and superficial appearance (most are grey or reddish brown), which has confused their classification. They were initially classified as lemurs. Tarsiers are prosimians (a primitive primate group) like lemurs, but their unique body structures and genetics set them apart as a separate species. Currently, there are seven species of tarsiers, and all but one are monotypic, meaning they do not have any subspecies.
“Tarsus” is the Latin word for ankle or heel, and it is the origin of the genus name for these long-legged primates with elongated heel bones. The Makassar tarsier’s species name “fuscus’ means dark in Latin and most likely refers to their darker coat color in comparison to other tarsiers in the region like the spectral tarsiers (T. Tarsier)
Size, Weight, and Lifespan
Tarsiers are small primates measuring about 5 inches (12.7 cm) from the top of their head to the base of their tail. Their long tail is around 9.4-10.2 inches (24 – 26 cm), and Makassar tarsiers have a visible bushy or tufted tip on their tail. Males weigh between 4.4 and 4.7 ounces (126 – 133 g), and females weigh around 4-4.3 ounces (113 – 124 g).
Research on wild and captive tarsiers is limited compared to other prosimians. Based on observations of closely related species, our best guess on the Makassar tarsier lifespan is between 10 and 16 years in captive individuals.
Appearance
These small primates have typical tarsier features, such as large eyes and muscular, long legs. Their legs account for about 25 percent of their body weight! Makassar tarsiers have reddish-brown fur that becomes darker brown on their thighs and paler near their feet. They have distinguishing thin Y-shaped black marks near their nose and a patch of bright white fur on the backs of their bat-like ears.
Their tufted tails can be a helpful tool for distinguishing tarsiers. The Makassar tarsier has a shorter, wiry tuft that widens towards the tip of the tail compared to the spectral tarsier (Tarsius tarsier), which has more extended and exaggerated hairs on their tuft.
Their claws are ideal for clinging to branches and prey as they travel through the forest. The claws on their second and third toes are modified to help them clean and groom themselves.
Tarsiers can watch their backs for predators! They are often seen clinging vertically onto trees, with their bellies near the tree trunk and their heads facing the opposite direction, looking for dangers approaching behind them. This ability to turn their heads 180 degrees in each direction comes from their unique spinal shape and muscle attachment.
Diet
Tarsiers are the only truly carnivorous primates that do not consume any non-animal foods. They hunt frogs, lizards, and even birds, but most of their diet consists of insects. The pads on their fingers are sticky, which helps them climb smooth surfaces and hold on to prey while hunting and feeding. They have sharp teeth with many cusps (sharp upward projections), ideal for catching prey as they leap in the canopy.
Behavior and Lifestyle
Tarsiers are nocturnal (active at night) and arboreal (tree-dwelling). Their anatomy and behavior are ideally suited to this lifestyle. Tarsier eyes are about the size of their brain, and they rely on their large eyes to see in low-light conditions and hunt in dense forests. Studies on the tarsier brain show that most of the neocortex (part of the brain dedicated to sensory and spatial perception or how a mammal moves around in its space using its senses) is made of particular nerves connected to their vision.
The most common form of movement is leaping and quadrupedal walking (using all four limbs). Using their long legs, they leap feet first and grasp tree trunks and branches with their toes. They can leap more than 16 feet (5 m)—over 30 times their body length!
Tarsiers engage in mobbing, a behavior in which they gather around a predator, such as a snake, and scream at it from a safe distance. Mobbing alerts everyone in the area that danger is nearby, and because the tarsiers actively look and yell at the predator, it is easy to pinpoint the location of the threat.
They make sleeping nests, which are vital to their breeding and survival. Makassar tarsiers use natural holes in trees, usually between 7 and 22 feet (2 and 7 m) high. Unlike most tarsiers, they also build nests near the entrances to caves. They can have multiple sleeping sites but use one primary site more often.
Tarsiers are the only wholly carnivorous primate that does not consume any plant matter.
Their eyes are almost the size of their brain!
Their brain is specialized to enhance their vision.
Makassar tarsiers make sleeping nests on tree cavities and in between rocks near the small Cave systems
They usually awake around dusk, as the last of the sunlight disappears and night falls. They leave their nest and travel as far as they can to forage for food. They have periods of high activity as they hunt for prey and rest in complete inactivity between these hunting bouts. These rests help conserve energy as they digest their food. Approximately 55% of the tarsier’s time is spent foraging or hunting, 23% traveling, and 16% resting. As the night progresses, they feed back toward their nest.
Tarsiers are territorial. Females and males protect their area of the forest from intruders of the same sex. Males are more tolerant of females because of the potential mating opportunities, and often, one male will have part of his territory overlap with multiple females. The estimated home range for tarsiers is about 1-3 acres (0.5-1 ha), which is quite large for such a small animal.
Group interactions vary depending on the species of tarsiers. No studies have been published on Makassar tarsiers yet. In general, tarsiers seem flexible on how much they tolerate other individuals. They can be solitary, where males and females only interact to mate. They have also been observed in groups, with a male, female, and young traveling and foraging together.
As active nocturnal predators, they are often too far away from other tarsiers to use visual expressions to communicate effectively. In dense forests, especially at night, using vocalizations is the best way to convey messages across long distances without the need to see each other. It is common for mated tarsiers to sing duets at dusk and dawn when they leave or return to their sleeping sites. The call usually starts with the female, which triggers a vocal response in the male. Duet calls are made to advertise their territory so other pairs or individuals know the area is occupied. Duets also serve as a way for couples to locate each other after a night of foraging to meet and go into their sleeping hollow together. Besides duets, tarsiers emit whistles, trills, and screams that convey different states of alarm and playfulness. More research is needed to understand better the context or the reason for these calls, especially in Makassar tarsiers.
Tarsiers are one of the few mammals that can use sounds at the ultrasonic frequency, which humans cannot hear. Using this frequency, tarsiers can access a secret channel that only they can tune into! We have yet to determine what kinds of information they are passing along through this type of communication, but it reveals an entirely new layer of the environment that they can interact with without competition from most other animals.
When tarsiers are close enough to see each other, they use gestures like snarls and folded ears to show fear or displeasure. An open mouth and a lunge are sometimes used as a defensive posture.
Compared to other prosimians (like lemurs), tarsiers have a reduced sense of smell. However, they still use glands on their lips, abdomen, and genital region to apply individual-specific hormones and secretions to branches as they climb trees. Tarsiers tend to scent mark more during the reproductive period of their activity cycle (for example, when a female is in estrus).
We need much more research on Makassar tarsiers in the wild before we can make specific claims about their reproductive and social behavior. However, the ranges of their biology will likely be similar to closely related tarsier species. We estimate that female tarsiers become sexually active when they are between 1.5-2 years old. When she is hormonally ready to mate (a condition called estrus), her genitalia (reproductive organs) may swell, a visual signal to males that she is prepared to mate. During this time, she also secretes hormones through her urine which additionally help males track or follow her. Pregnancy lasts 5-6 months (the gestation period), after which, she gives birth to a single child (twins are rare).
Tarsier babies are relatively large, weighing around 0.8 ounces (23 g), which can be close to a quarter of an adult’s weight! They are born precocious, covered in fur, and with open eyes—infants have completed much of their physical development in their mother’s womb. Infants are carried and cared for by their mothers for at least the first ten days, after which they show signs of independence as they venture away from their mothers to explore their new world. Young tarsiers are often “parked” or left alone in a safe spot while the mother forages for food nearby.
In some tarsier species, young tarsiers start leaping from branches when they are only 32 days old! A 2.5-month-old tarsier can hunt independently and no longer depend on their mother for milk.
In general, there is a lot of variation between the species of tarsiers regarding their social behavior. Researchers thought tarsiers were solitary (living alone) or monogamous (living as part of a pair), but many species have been observed to tolerate living in larger groups. It may be that their sociality (how tolerant they are to living in groups) depends on the sex of individuals in the area and the quality of the environment. A male tarsier can have overlapping home ranges with multiple females and mate with more than one of them, but he will not tolerate another male in that home range. This behavior ensures that the male can maximize the spread of his genes and keep his competitors out. Some have observed that tarsiers tend to avoid living in larger groups in disturbed areas where food sources may be scarce, which prevents competition over food and increases overall survival.
Tarsiers are the only entirely carnivorous primates. The voracious predators on Sulawesi are essential in creating a balance between highly reproducing organisms like insects and lizards, whose populations can multiply without predators such as tarsiers.
The plasticity of the tarsier diet, capable of switching between insects and vertebrates depending on which is more abundant, is an ecological advantage for the island, where small changes in available nutrients have significant adverse effects as time passes. Tarsiers keep the biomass and nutrients in check by feeding on different prey types.
Predators like snakes, monitor lizards, civets, and owls prey on tarsiers, making tarsiers an important nocturnal food source.
The International Union for Conservation of Nature lists Makassar tarsier as Vulnerable (IUCN, 2020), appearing on the IUCN Red List of Threatened Species.
Habitat loss and degradation are the most significant threats against the surviving members of the Makassar tarsier population and other wildlife in Sulawesi. Most native forests have been cut down for resources or converted to agricultural land. This has a cascading effect of reducing tarsier habitat and introducing pesticides into the environment, which can poison insects, an important tarsier food source.
Tarsiers that live in edge forests near people are invariably caught and kept as pets because of their cute appearance. Unfortunately, tarsiers do not handle captivity well and often die after a few days of being captured. In these areas, domestic dogs and feral cats kill populations of tarsiers.
The Makassar 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.
The Makassar tarsier’s main hope against extinction is habitat protection. Within their range, there are a few protected habitats, such as the Greater Maros Conservation Area, where development is restricted.
National and international laws protect them against hunting and trade. However, there is a lack of scientific studies on Makassar tarsiers, and therefore, it is difficult to take specific measures to increase their population. So, despite the current conservation measures, the population is decreasing.
Some non-governmental organizations are conducting important fieldwork to bridge the connection between tarsiers, ecology, and human society. Some of this work includes bans on using harmful pesticides that can poison the tarsier’s food chain and environment.
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Written by Acima Cherian, August 2024