Big-eyed tarsiers: Tarsiers have remarkably large eyes, about 1.6cm. Each eye is bigger than the entire brain and larger than the stomach. So much so that they cannot move their eyes within the sockets. Instead, they special modifications to their neck vertebrae allowing them to rotate their heads nearly 360 degrees, even though they seem to have almost no neck! Unlike most other nocturnal creatures, however, tarsiers do not have a reflective layer behind the eyes (tapetum). They have excellent hearing, using their large funnel-like ears which are hairless, and thin and membranous. They can furl and unfurl their ears.
Size: Body 8.5-16cm long, tail 13.5-27.5cm long, 80-165g.
Lifespan: 8-13.5 years. Babies: One young born. Gestation 178 days (rather long for such a small creature), no specific breeding season, maturity at 1 year.
Distribution: Only in Southeast Asia including islands:
Habitat: Only in dense vegetation, usually in lowland rainforest, secondary forests and mangroves. But some like the Western tarsier can be found in cultivated lands and even gardens.
Classification: Family Tarsiidae. There are 3 (some say 4-5) species of tarsier.
Philippines tarsier (Tarsius syrichta): most common in Mindanao, southeastern Philippines and the islands nearby, but also found in Sumatra and Sulawesi.
Western/Bornean/Horsfield's tarsier (T. bancanus): Borneo, Sumatra and Banka
Spectral/Celebes/Sulawesi tarsier (T. spectrum): Sulawesi and nearby Great Sangihe, Peleng and Selajar. Pygmy Tarsier (T. pumilus): central Sulawesi Diana's Tarsier (T. dianae)
The Spectral tarsier developed fewer adaptations, e.g., it lacks adhesive toes. Fossils suggest tarsiers ranged throughout Asia, Europe and the Americas. Leaping tarsiers: Tarsiers are outstanding leapers, jumping up to 10 times their body length (2-3m sideways and 1.5m upwards). The longest leap is 5-6m. They look very much like furry frogs! Their hind legs are disproportionately long, almost twice the body length. In fact, they are named for their special elongated ankle (tarsal) bones, in which the tibia and fibula are fused in the lower portions and thus act as shock absorbers.
When they land, they grip strongly with their long and slender fingers and toes, which are tipped with ridged swellings which act like suction cups (in fact, tarsiers can move up glass surfaces with these suckers). The thumb is not opposable but the big toe is.
Their long tail is naked except for few hairs at the tip, and has ridges underneath like the ridges on our hands and feet. They use their tails like a tripod when they are stationary, and to control rotation during their leaps.
They leap quickly through the dense vegetation, often twisting in mid-air. They are vertical leapers and clingers. On the ground they hop like little kangaroos, holding their tails arched over their backs. On the ground, they can make leaps up 1.2-1.7m. To move more slowly, they climb either by hauling themselves up with their front limbs or pushing themselves up with their back legs. They can also slide down a vertical branch on all fours.
Terrible hunters of the night: Tarsiers are pure carnivores, unique among primates. They eat mainly insects (cockroaches and crickets) but also hunt and kill small vertebrates. They even kill venomous snakes, birds larger than themselves (roosting birds are particularly at risk), scorpions and bats. Those living in mangroves also hunt small fish and crabs. Tarsiers are voracious and eat up to 10% of their body weight each day. They often eat all parts of the prey including feathers, beaks, feet, exoskeleton.
They find their prey by sight and through their excellent hearing. They fix onto the prey with their huge soup-plate eyes, rotating their head through 180 degrees if necessary. Their constantly moving radar-dish ears also pin point the location of prey. They stealthily creep up to it, position themselves careful, then capture they prey by leaping with their strong long hind legs. They grab the prey in their strong hands and kill with a few bites of their large, extremely sharp needly teeth, their short muzzle giving them a strong bite. Just before and during the killing strike, they shut their large eyes tightly to prevent injury to their eyes. They then rely on their ears to continue to guide them to the right spot. Tarsiers drink regularly, licking water off vegetation and even going to the ground to lap from a pool or stream. Tarsiers need to be near a source of open water.
The Odd Ones Out: The Dry-Nosed prosimians Tarsiers don't fit neatly into either the prosimians or anthropoids. They share characteristics of both suborders, with features unique to themselves. Tarsiers are often lumped together with prosimians because they look and act like them: small, nocturnal, toilet claw, elongated legs.
An example of their in-between features: all digits have flattened nails except for the second and third hind toes, which have "toilet claws" for grooming (a prosimian feature). But they don't have the dental comb that prosimians have.
Unlike lemurs and other prosimians, and more like monkeys and apes, tarsiers don't rely as much on smell. Tarsiers have dry noses more similar to monkeys. The tarsier’s eye structure clearly indicates that it had a diurnal ancestor; it has a focusing point in the retina known as a fovea which is useful only in daylight. And it lacks the tapetum. Like other anthropoids, females also have skin swellings when they are ready to breed. They are brave and fierce hunters, moving actively through dense vegetation during the night. They are most active at dusk when their prey is most active. They usually hunt about 1m above the ground. During the day, tarsiers move up higher to sleep in dense vegetation clinging to thin branches, propped up by their long, nearly naked tails that they press against the branch. They rarely sleep in hollow trees. Their fur is thick and silky, helping these tiny creatures to conserve heat. Sleeping tarsiers are rarely eaten by snakes. It is suggested that they reduce their body temperature and thus become 'invisible' to snakes who hunt by sensing body heat.
A terror of tarsiers: Tarsiers are usually found in family groups (based on a stable pair bond) or by themselves. They may hunt alone but return to sleep together. They may rest with their tails intertwined! But tarsiers prefer to groom themselves and only groom each other during mating season. To groom, they use their toilet claws on their feet, or lick their fur. Tarsiers are quite strongly territorial. The territory of each gender is exclusive, with the male having a larger territory that overlaps those of several females. Tarsier talk: Sounds and smell play the major roles in communication. Although tarsiers make less noise than other primates, they do have a wide range of calls. These include a loud piercing single note to announce their whereabouts to other tarsiers. This allows tarsiers to avoid each other as they hunt. When contented they make a soft bird-like trill and when being friendly in a group, chirp like locusts. When females are ready to breed, they make a special call. A mated pair also perform duets to strengthen their bonds, and their juvenile offspring may join in. Most of the tarsier’s calls are extremely high-pitched, many are beyond human hearing. On the other hand, their scent messages are quite strong and well within the range of the human nose!! They scent mark with urine and by rubbing secretions from their scent glands onto bark and vegetation from scent glands on their chest (epigastric gland).
Tarsier babies: Tarsiers breed throughout the year, usually only one baby is born. The gestation period of about 6 months is long for such a tiny creatures. But the newborn is quite well developed: fully furred, with eyes open and can climb on its first day of birth, make short leaps in four days and begin hunting in about 40 days. Of all primates, a newborn tarsier is the biggest relative to the mother, about 25% her body weight! The mother doesn't make a nest for the baby and carries it with her. She has several nipples but only one pair produces milk, the others appear to act more as anchoring points for the baby. Although the baby can cling to the mother, she may carry it in her mouth when she is in a hurry. She may park her baby as she hunts. The baby keeps in contact with mum through soft clicks and whistles. The baby is able to take solids in a week and to hunt for itself in 3 months. But it continues to drink mum's milk.
Role in the habitat: Like other hunters, they keep populations of their prey under control. They are also food for other creatures higher up in the food chain, e.g., owls, wild cats, snakes. To scare off predators, a tarsier will close its eyes when a predator comes near, then suddenly open its eyes and bare its sharp teeth to surprise the predator when it comes closer. By startling the predator, the tarsier has a better chance to leap to safety.
Status and threats: CITES 2 for all subspecies. There are only about 1,000 Philippines tarsiers left in the wild, they are found in only a few areas of Northern Mindanao. In the 1970s, there was a demand for them for science experiments, and as pets or stuffed souvenirs. They make poor pets as they need live food and lots of it. They often die within days of capture due to lack of food. Some are so traumatised by captivity that they kill themselves by banging their heads against the cage.
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