HORSFIELD'S TARSIER

Cephalopachus bancanus

Geographic Distribution and Habitat
Horsfield’s tarsier, also known as the western tarsier, is native to Southeast Asia occurring in Borneo (Asia’s largest island and the third-largest island in the world), Indonesia, and Malaysia.

In Borneo, this tiny, bizarre-looking primate is found in the sovereign state of Brunei, located on Borneo’s north coast; and within Borneo’s Bukit Baka-Bukit Raya National Park, located in western Kalimantan where the species has been recorded at elevations of 4,000 ft (1,200 m). More typically, however, Horsfield’s tarsier is found in lowland areas below elevations of 329 ft (100 m).

In Indonesia, the species occupies several islands, including southeastern Sumatra where the boundaries of the Musi River are thought to demarcate this tarsier’s territory.

In Malaysia, the Horsfield’s tarsier is found in the states of Sabah and Sarawak.

Tarsiers reside in a wide variety of habitats; Horsfield’s tarsier seems to prefer the edge of secondary forests, where young saplings and secondary vegetation are plentiful. However, the species also dwells in primary forests, in shrubby coastal areas, and at the edge of plantations.

TAXONOMIC NOTES

At one time, Horsfield’s tarsier was placed in the genus Tarsius with all other living tarsiers. Today, however, the species is recognized as being distinct from the Philippines tarsier and from the various tarsiers of the island of Sulawesi in Indonesia and other nearby islands. To account for this distinction, scientists placed Horsfield’s tarsier in a separate genus, Cephalopachis. (C. banacanus is the species name.) Further study is warranted, scientists say.

Currently, four subspecies of Horsfield’s tarsier are recognized:

  • Tarsius bancanus bancanus occurs in southeastern Sumatra and on the island of Bangka in Indonesia. (Classified as Endangered.)
  • The Bornean tarsier (Tarsius bancanus borneanus) occurs in Brunei, Kalimantan, and the Karimata Islands, Indonesia, as well as in Sabah, Sarawak and Borneo, Malaysia. (Classified as Vulnerable.)
  • The Natuna Islands tarsier (Tarsius bancanus natunensis) occurs on Serasan in the South Natuna Islands, and possibly nearby on Subi Island, Indonesia. (Classified as Critically Endangered.)
  • The Belitung Island tarsier (Tarsius bancanus saltatory) is found only on the island of Belitung, Indonesia. (Classified as Endangered.)

TARSIERS ARE UNIQUE PRIMATES

The tarsier family (Tarsiidae) includes 3 genera, and at least 14 species and 7 subspecies. However, the taxonomy of the species continues to be debated.

Tarsiers are prosimians who belong to the suborder Haplorrhini, or “dry-nosed” primates, along with the true simians (monkeys, apes, and humans). Haplorrhines are considered to be less primitive than those belonging to the suborder Strepsirrhini, or “wet-nosed” primates. Strepsirrhines include lemurs, aye-ayes, lorises, and galagos (bush babies).

Haplorrhines diverged from Strepsirrhines 63 million years ago.

While Strepsirrhines retained their ability to make Vitamin C, haplorrhines (including tarsiers) did not. Another distinction between the two is the “disconnected” upper lip that characterizes haplorrhines, allowing for their facial expressions.

Some scientists believe that tarsiers deserve a narrower taxonomic classification, asserting that tarsiers occupy a small evolutionary branch between haplorrhine simians and strepsirhine prosimians.4

Horsfield's Tarsier geographic range. Map: IUCN, 2008

Size, Weight, and Lifespan
Head-to-body length for Horsfield’s tarsiers is between 4.5 and 5.8 in (11.5 to 14.5 cm). Their long tails add another 8 to 9.3 in (20 to 23.5 cm).

Males are heavier than females, with a weight between 4.3 and 4.8 oz (122 to 134 g). Females weigh between 3.8 and 4.5 oz (107 to 127 g).

Lifespan for Horsfield’s tarsier is 15 years in the wild.

Appearance
With a face like Uncle Fester, the loveable but ghoulish uncle in the 1960s American television sitcom, The Addams Family, featuring an eccentric but benevolent family, or like Gollum, the swamp-dwelling hobbit of the fantastical, magical Lord of the Rings—or, if your imagination won’t allow these comparisons, then think of a face like a strange-looking owl or bat—Horsfield’s tarsier elicits an automatic “Oh, my!” by anyone casting a gaze upon this startling primate.

Extraordinarily large, yellowish-brown eyes take up the upper face of this diminutive creature; a nondescript muzzle occupies the lower portion, falling into a short neck. Thin, almost translucent, scalloped ears are fitted on either side of a round head.

Soft and wavy fur covers the tarsier’s small and stocky body, with a coat color that is usually buff or gray-brown to brownish, sometimes varying to pale olive or reddish brown. Underparts are buff or grayish, and the tarsier’s long tail is hairless except for the tip, where a well-developed tuft of hairs congregates.

Horsfield’s tarsiers have short forelimbs and greatly elongated hind limbs that allow them to jump up to 16.5 ft (5 m), about 40 times their body length, between branches. Long, thin fingers and toes are fitted with large pads at the tips that allow tarsiers to tightly grab branches and prey. Fingernails and toenails are flattened, except for the second and third toe digits, which function as grooming claws used to remove dead skin and parasites.

What Does It Mean?

Primary forest:
Also termed old-growth forest, virgin forest, or primeval forest—a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community, an ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment.

Secondary forest:
A forest that has regrown after a major disturbance, such as fire or timber harvest, but has not yet reached the mature state of primary forest.

Secondary vegetation:
Vegetation that has regrown after a major disturbance, such as fire or clearance.

Subspecies:
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Visit the Glossary for more definitions

Diet
Tarsiers are the only entirely carnivorous primates. Their medley of insect snacks and “tapas” include beetles, cockroaches, locusts, moths, grasshoppers, butterflies, ants, and cicadas. For heartier meals, Horsfield’s tarsiers eat birds, bats, frogs, and snakes—including poisonous species.

Under the cover of darkness, these nocturnal primates patiently wait for prey to approach. Tarsiers have keen hearing and locate their prey primarily by sound. Their ability to rotate their head 180 degrees in each direction allows them to easily spy, and then ambush, potential dinner victims. From a fixed position, Horsfield’s tarsiers can reach out and grab a bird or bat, sometimes midflight; or they might choose to leap upon their intended target. Tarsiers kill their victims with multiple bites to the back of the neck. Gripping these now lifeless bodies in their hands, they devour them, starting with the head and working down the body with their powerful jaws and teeth.

Wide mouths (relative to their overall size) allow tarsiers to consume larger prey. They eat about 10 percent of their body weight every 24 hours. Meals are washed down with water that the tarsiers obtain by licking drops from bamboo leaves, rain runoff from the barks of trees, or a pool of water.

Behavior and Lifestyle
Horsfield’s tarsier is a nocturnal, arboreal species: they are primates who are active at night, who sleep all day, and spend nearly all their time in the trees. Awakening just before sunset, tarsiers allow themselves 10 or 20 minutes to wake up before they begin foraging in the forest understory where they leap effortlessly from branch to branch, thanks to their powerful leg muscles. They may also hop or walk quadrupedally (on all fours). Their long tails help them to balance when they are reaching out to grab prey. Although they rarely travel on the ground, Horsfield’s tarsiers forage at an elevation only 6.5 to 16.5 ft (2 to 5 m) above. They sleep at this relatively low elevation, too, in a tangle of vines, all alone.

A group consists of a monogamous breeding pair and their young offspring, occupying a small home range.  Highly territorial, tarsiers scent-mark their area with urine and glandular secretions. They will also chase and shriek loudly at intruders who do not get the message to “keep out.”

Fun Facts

Horsfield’s tarsier is named after the scientist who first described this species.

Daily Life and Group Dynamics
A group consists of a monogamous breeding pair and their young offspring, occupying a small home range.  Highly territorial, tarsiers scent-mark their area with urine and glandular secretions. They will also chase and shriek loudly at intruders who do not get the message to “keep out.”

Communication
Besides territorial scent marking, shrieking at and aggressively chasing away intruders, Horsfield’s tarsiers employ other communication techniques.

Specific vocalizations include courtship calls, used by both adult males and females. A male will emit two to three “chirrups” while opening and closing his mouth, with his gaze fixed upon the female object of his desire. If she is receptive, the female will undulate provocatively, showing the male her genitals. If she is not receptive to the male’s charms, however, the female will emit an unfriendly and threatening call and may bite the male or push him away.

Mothers use high-pitched calls to stay in contact with their infants. Infants emit a series of clicking sounds: “k,” “tk,”, “ki” or a rapid “kooih” when they want mom’s attention.

Social grooming occurs only between mothers and infants.

Reproduction and Family
Horsfield’s tarsier becomes sexually mature at around a year old, and breeding occurs throughout the year.

After a gestation period of about six months, females give birth to a single infant. Infants cling to their mother’s belly; when mothers travel, they carry their babies inside their mouths and deposit them on a branch while they hunt for prey.

Infants are born with their eyes open and with a full fur coat. They are able to groom themselves and are able to climb at just 1-day old. At 7 to 10 days old, they can use their tails as support while in a resting position; around 1-month old, they are able to leap between trees. At about 42 days old, now fully weaned from their mothers, the young begin to capture their own prey.

Young Horsfield’s tarsiers leave their home range at the onset of puberty to establish their own territory elsewhere.

Photo credit: Bernard DUPONT/Creative Commons

Ecological Role
Through their diet, tarsiers help to regulate insect and small vertebrate populations. They, themselves, are a food source for a variety of large rainforest predators.

Conservation Status and Threats
Horsfield’s’ tarsier is classified as Vulnerable by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. Vulnerable means that the species faces a high rate of extinction in the wild.

Habitat loss is the primary threat facing Horsfield’s tarsier. Where lush tropical rainforests once provided ample habitat, palm oil plantations and agricultural tracts now occupy the land. The logging industry, along with fires, have also destroyed much of the tarsiers’ habitat. Although they tolerate a measure of habitat disturbance and do well in secondary habitats, Horsfield’s tarsiers do not migrate over long distances. Deforestation, therefore, poses a seriously adverse effect on the population. The species also suffers from the toxic effects of agricultural pesticides.

Additionally, Horsfield’s tarsier is threatened by the illegal pet trade, particularly in Lampung and Way Kambas National Park in Indonesia. But this species fares horribly in captivity, usually dying within days of capture.

Conservation Efforts
Horsfield’s 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. However, as is often the case with endangered species, laws created to protect them are largely ignored and difficult to enforce.

But in 2007, with great initiative from the World Wild Fund for Nature (formerly known as the World Wildlife Fund), or WWF, the governments of Brunei, Malaysia, and Indonesia worked together to create a large protected area for Horsfield’s tarsier. Known as the “Heart of Borneo” and considered Asia’s last great rainforest, 85,000 sq mi (220,000 km) has been designated as protected habitat. Nongovernmental organizations (NGOs) helped to broker this critical environmental initiative.

​​References:

  • http://www.arkive.org/horsfields-tarsier/tarsius-bancanus
  • http://www.iucnredlist.org/details/21488/0
  • https://a-z-animals.com/animals/tarsier
  • https://www.mnn.com/earth-matters/animals/stories/tarsiers-cool-facts-about-these-wonderfully-weird-primates
  • https://en.wikipedia.org/wiki/Horsfield%27s_tarsier
  • https://www.youtube.com/watch?v=tojoI8-zoM8
  • https://www.youtube.com/watch?v=X2rt0XCcvi0
  • http://www.endangeredspeciesinternational.org/tarsiersection/?gclid=Cj0KEQjw4cLKBRCZmNTvyovvj-4BEiQAl_sgQgBnH2ZSASxjBKRYk4HYZF_UBK6TwK50_iYrP3u5jQUaAmlH8P8HAQ
  • https://seaworld.org/Animal-Info/Animal-Bytes/Mammals/Western%20Tarsier

Written by Kathleen Downey, June 2017