This cute little guy is a Philippine tarsier (Carlito syrichta). He is often called “the world’s smallest monkey,” but this is not fully accurate. The problem isn’t one of size, but of classification. Different scientists classify the tarsiers either as prosimians or as anthropoids. Whatever the classification, it is clear that tarsiers share traits with both groups. Like prosimians, tarsiers are nocturnal and have grooming claws, as well as a bicornuate uterus. However, like anthropoids, tarsiers lack a tapetum but have post-orbital closure and monthly sexual swellings in females.
On average, the Philippine tarsier is only 11-14 cm long without the tail, which is about twice the length of the body. They only weigh around 120-130 grams. The species is sexually dimorphic, with males being larger and heavier than females. Their fur is usually gray, and their very long tails are nearly bald, although there is a fur tuft at the very tip. Tarsiers get their name from their very elongated ankle bones. Tarsiers’ tibia and fibula are fused at the bottom, and this absorbs shock as the animal leaps up to 3 meters from tree to tree.
As you probably noticed immediately, tarsiers have incredibly large eyes. In fact, tarsiers’ eye sockets are larger than both their brain case and their stomach. The eyes are so large that they do not even turn inside the orbit, so to look side to side, a tarsier must swivel its head. However, like owls, tarsiers have a special joint that allows them to rotate their heads 180 degrees in either direction. This allows them to make very accurate leaps directly backward. Tarsiers are nocturnal, but unlike most nocturnal primates, they do not have a tapetum (the reflective surface in the eye to aid with night vision).
Tarsiers are arboreal, preferring primary or secondary growth forests, specifically dense, low-lying vegetation. Physically, they are very well adapted for vertical clinging and leaping. They live in groups consisting of multiple pairs. Unlike most other primates, tarsiers are completely carnivorous. While their primary prey is insects, they will also eat small bats, birds, and even reptiles.
Philippine tarsiers have estrus cycles of 25 to 28 days, and their pregnancy lasts around 6 months. Interestingly, after mating, the male will insert a “mating plug” into the female. After birth, young are carried in the female’s mouth, and will quickly learn to cling and leap.
Tarsiers are only kept in zoos rarely and sporadically, and even then usually only in the Philippines. This is due in part to tarsiers only eating live prey, which is somewhat difficult for some zoos to provide consistently. Another large reason tarsiers are not often found in zoos is that once there, they “commit suicide.” Once captive, they quickly begin to engage in stereotypy. In tarsiers, stereotypy is unfortunately manifested in them banging their heads against objects. Because of their relatively small and thin skulls, this frequently results in death, hence the anthropomorphization that they are committing suicide. However, tarsiers are sometimes kept as pets in the Philippines, although this is ill advised.
Philippine tarsiers have only been known to the Western world since the early 18th Century. The first published description, by a J. Petiver, came in 1705. In the modern era, tarsiers are threatened in almost every place they inhabit. One of the biggest threats they face is slash-and-burn agriculture, which completely wipes the land clear of the forests and scrublands on which they so heavily rely. Fortunately, tarsier conservation efforts have begun within the past few decades. Two major players in this area are the Philippine Tarsier Foundation, Incorporated and Project Tarsius. Much headway has been made: in the past few years, the Philippine tarsier has been recategorized. While it was formerly classified as “endangered,” it is now classified as “threatened.” This is a major step in the right direction for the Philippine tarsier.
Watch this! Some “Facts” about the Tarsier
Sources: Philippine tarsier videos, photos and facts – Tarsius syrichta – ARKive, The Philippine Tarsier, Philippine Tarsier Foundation, Inc. | The Philippine Tarsier, ADW: Tarsius syrichta: CLASSIFICATION, Endangered Species International, Tarsiers: The Misfit Primates, Philippine Tarsier Foundation, Inc. | Tarsier Conservation Efforts Gains International Attention, Project TARSIUS – Research and conservation of the Philippine tarsier (Tarsius syrichta), Species Profile for Philippine tarsier (Tarsius syrichta)