Geographic Distribution and Habitat
The Philippine tarsier (Carlito syrichta) is native to the southeastern Philippines. While tarsiers once ranged across Europe, northern Africa, Asia, and North America, they all now live in the lush islands of Southeast Asia. Twenty thousand years ago, the Philippine islands—all 7,107 of them—were linked together as larger islands because the sea level was much lower than it is today. The rising seas have effectively split the land forms, but these smaller islands are still grouped together by the animal life that has evolved on them. There are about six of these regions—known as “faunal regions”—and Philippine tarsiers are native to what’s known as the Mindanao region. Philippine tarsiers live in rainforests up to an elevation of 2,460 feet (750 meters) and are tolerant of edge habitat and secondary forest, although their population density is lower in these disturbed habitats. They favor small trees, grasses, bushes, and bamboo shoots to move about in.
TARSIERS ARE UNIQUE PRIMATES
Tarsiers are a unique group of primates, an intermediate form between lemurs and monkeys. While they are classified in the suborder Haplorhini with monkeys and apes, making them more related to them than to lemurs, they occupy their own intraorder, Tarsiiformes. Their taxonomy is still debated by experts. Some consider all tarsiers to belong to the same genus, Tarsius, while others have split the Philippine tarsier into its own genus, Carlito, and another species, Horsfield’s tarsier (or the western tarsier) into the genus Cephalopachus. Many also believe Philippine tarsiers to have three subspecies: the nominate Philippine tarsier, C. s. syrichta, from the islands of Leyte and Samar, the Bohol tarsier, C. s. fraterculus, from Bohol, and the Mindanao tarsier, C. s. carbonarius, from Mindanao. Some scientists believe C. s. fraterculus and C. s. carbonarius to be synonymous, some believe there to actually be four distinct subspecies, and some don’t believe there is enough evidence to support any subspecies at all. Clearly, there is plenty of research yet to do in tarsier taxonomy.
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 strepsirrhine prosimians.
Size, Weight, and Lifespan
As one of the smallest primates on earth, their body is only about 4.5 to 5 inches (11–13 cm) in length on average, with a tail about double that length. They weigh between 4 and 5 oz (110–130 g). Tarsiers are shorter-lived than many other primates. One Philippine tarsier lived to 13 years of age in captivity, and lifespan in the wild is likely shorter than this.
Philippine tarsiers resemble what a cross between a lemur and a tree frog might look like. All species of tarsier look similar to each other, and they can be difficult to differentiate. Their body is overall very small and covered in gray hair, although Philippine tarsiers may have a slightly paler and more yellow hue than other tarsiers.
Front and center of their proportionally large head are their extraordinarily large eyes, made all the more dramatic by their very small—at least in daylight—pupils. In fact, tarsiers have the largest eyes in proportion to their body of any mammal, each one heavier than their brain. This is likely due in part to their lack of the reflective layer of tissue that most nocturnal mammals have, called the tapetum lucidum. This is what causes your dog’s or cat’s eyes to glow when you shine a light towards them at night. It helps these animals take in more light when it’s dark out. Without it, tarsiers have massive eyes to take in as much light as possible at night.
Thanks to their unique spines, their heads can turn nearly 180 degrees around, like an owl. This is a necessity because their eyes are so big that they can’t move them in their sockets to look around. Their large ears stick straight out from the sides of their heads. These features give them exceptional sight and hearing, making them very well adapted to their nocturnal environment.
They are often found gripping onto vertical branches and shoots, and this position exaggerates their alien-like hands and feet. They have very long fingers and toes that end with swollen adhesive pads that help them to grip onto branches. Their feet contain two very elongated tarsal bones that give them amazing leaping abilities. In fact, the word “tarsier” is a reference to these elongated tarsal bones. Due to these elongated leg bones and the powerful muscles wrapped around them, their legs alone comprise about a quarter of the weight of their entire body.
They also have two grooming claws on each of their feet, which are hairless for the most part. Their tail is long, thin, and bald, like a mouse’s. The lack of hair on their tail and feet is another way to tell Philippine tarsiers apart from other tarsiers, as most other tarsier species have at least some hair on these body parts. There is no notable sexual dimorphism among Philippine tarsiers.
Tarsiers are the only fully carnivorous primates, consuming no plant material whatsoever. Philippine tarsiers mainly feed on insects and other small animals, such as frogs, lizards, and even small birds.
Behavior and Lifestyle
Philippine tarsiers don’t often move quadrupedally. Instead, they tend to cling vertically to trees, using their tail for support, and can usually be found leaping about the rainforest. They can leap 20 feet (6 meters) at a time—pretty amazing for such a small animal! They can move extremely quietly. They tend to stick to just 3 to 6 feet (1–2 meters) off the ground. They are not particularly fearful, even of humans, unless there is quick movement.
As their giant eyes might suggest, Philippine tarsiers are nocturnal and well-adapted to their dark environment. They are also fully arboreal, spending the day hiding amidst thick vegetation and emerging at night to hunt. A study on spectral tarsiers (T. tarsier) found that they spend 55% of their waking hours foraging, followed by 23% traveling, 16% resting, and 6% engaging in social activities. Philippine tarsiers likely spend their nights similarly. During the dry season, they likely spend more time foraging and traveling as food resources are less plentiful. They sleep in areas of dense vegetation close to the ground, usually near the edge of their home range. They usually have three or four sleeping sites that they use regularly.
If human eyes were as proportionally large as tarsiers’, they would be as big as grapefruits!
While Philippine tarsiers are social, they are most often seen in male-female pairs, or occasionally in small groups of about four individuals. Their home range size is about 1 to 2 hectares, and this likely expands during the dry season. One study found that females travel an average of 3,700 feet (1,100 km) per night, and males travel about 5,400 feet (1,600 m) per night on average. An individual’s home range overlaps considerably with members of the opposite sex, but only slightly with members of the same sex. Male tarsiers are known to be fiercely territorial, even fighting other males to the death for trespassing onto his territory.
Tarsiers aren’t as vocal as most other primates, although they let out a high-pitched squeak when in danger. They also occasionally vocalize to maintain their territory and keep track of their mate. They use olfactory communication extensively, scent-marking from urine and gland secretions to maintain their territory. Although not much information is known about visual communication, it is likely also important because of their exceptional eyesight. Tactile communication is mostly used between a mother and her baby.
Philippine tarsiers are most likely monogamous, as are other tarsier species. They breed year round, although some research indicates they may breed more when insects are more readily available. Females give birth to a single baby after about a six month gestation. Babies are born fully furred and with open eyes. When they are only two days old, they can begin to climb about and explore their environment—and two days later, they can leap, although they keep very close to their mother at this age. She carries her baby in her mouth or on her belly. At 19 days of age, the young are able to move about nearly as gracefully as their parents. When they are just 45 days old, they are able to catch their own prey and are weaned at about the same time. Interestingly, females have multiple pairs of nipples, although they only use one pair for nursing. It is unclear what, if any, role the father plays in rearing offspring.
It is not known for sure what animals prey on Philippine tarsiers, although they are likely a food source for owls and other nocturnal carnivores such as civets, lizards, and arboreal snakes. They are predators themselves to the variety of small animals that they eat.
The International Union for Conservation of Nature lists Philippine tarsiers as Near Threatened (IUCN, 2015), appearing on the IUCN’s Red List of Threatened Species. There are unfortunately a variety of threats facing Philippine tarsiers. Habitat loss, as for many primates, is a major concern. There is very little primary habitat left in their native range. While they can survive in disturbed habitat, their population densities are lower in these areas. They require specialized habitat to thrive, with lots of low, bushy vegetation and plentiful insects and small animals. Insects are unfortunately facing a conservation crisis of their own, with an estimated 9% loss of insect abundance per year. Such a loss demonstrates the interconnectedness of life, as this dramatic decrease is sure to impact Philippine tarsiers’ food availability in the years to come.
Their infant mortality rates are also very high, both in the wild and captivity, making it difficult to recover populations. They also have high population densities over a relatively limited geographical range, meaning that disturbance, either natural or human-caused, in their range can have devastating impacts on the population. Philippine tarsiers are also a prime target for the pet trade. While it is illegal, they are a common sight in the pet markets of Manila and are a popular pet in Mexico. Tarsiers do not tend to live long as pets, as their diet is very specialized, requiring large quantities of live insects, and they have been known to engage in self-injurious behavior as a result of captivity.
In recent years, tourism has emerged as a possible threat to Philippine tarsiers. Travelers are making trips to the Philippines specifically to see this iconic and unique species in the wild. While this has helped locals to view them in a positive light and as a priority for conservation, thanks largely to the tourism money they bring in, it may have overall negative consequences for the animals. They are captured specifically for tourist facilities, where the tarsier is displayed for viewing during the day—not ideal for a nocturnal animal. Because tarsiers are difficult to breed in captivity, new individuals must be collected from the wild for these displays. Additionally, it is thought that these tourism facilities may fuel the pet trade, as people may be so charmed by the tarsiers that they will purchase one as a pet. Many facilities even sell them as pets directly to tourists.
Philippine tarsiers are listed under Appendix II of the Convention on International Trade in Endangered Species (CITES) and are protected by law in the Philippines. More research is needed, specifically about what kind of habitats they can survive in and on their taxonomy. Captive breeding has been attempted but has been largely unsuccessful. Education attempts have focused on promoting Philippine tarsiers’ ecological values to local people, such as their pest control benefits, instead of their values for tourism and the pet trade.
- Řeháková, M. 2019. Successful breeding attempt of a pair of Philippine tarsier (Tarsius syrichta) in a conservation center in Bilar, Bohol, Philippines and recommendations for tarsier husbandry. Zoo Biol. 38(6):516-521. doi: 10.1002/zoo.21501.
- Van Klink, R., D. E. Bowler, K. B. Gongalsky, A. B. Swengel, A. Gentile, J. M. Chase. Meta-analysis reveals declines in terrestrial but increases in freshwater insect abundances. Science 368(6489):417-420. doi: 10.1126/science.aax9931.
- Wojciechowski, F. J. K. A. Kaszycka, J. B. Otadoy. 2021. Utilizing local community knowledge of the Philippine tarsier in assessing the Bilar population endangerment risk, and implications for conservation. Journal for Nature Conservation (62). doi:10.1016/j.jnc.2021.
- https://www.itis.gov/servlet/SingleRPhilippine tarsier/SingleRPhilippine tarsier?search_topic=TSN&search_value=944114#null
Written by K. Clare Quinlan, Mar 2022