Western Tarsier

1. Introduction

Bornean tarsier or Chepalopachus bancanus borneanus is a subspecies of Western tarsier, Chepalopachus bancanus that are known to inhabit Borneo Island. It is a nocturnal and carnivorous primate with unique features and interesting facts. Such unique features include the long anklebones known as tarsals as attribution to its name, Tarsier, and large eyes that weigh more than its whole brain. As for an interesting fact, infant tarsiers are born larger relative to their parents with open eyes and fur.

The conservation status for C. b. borneanus is endangered according to International Union for Conservation of Nature (IUCN) Red List (2008) and its population size is declining over time. Its major threats include habitat destruction and hunting for pet trade. It is difficult for tarsiers to live and survive in captivity and up until now, captivity management of tarsiers has yet meeting its effectiveness. It is presumed that tarsiers only eat live food that cannot be obtained in zoos, further complicating by its reproductive life in the wild. Consequently, over half of the tarsiers captured in wild died within two years in captivity. Furthermore, infant mortality rate and reproduction rate of tarsiers were observed higher in captivity (Gron, 2010; Endangered Species International Inc., 2011). Therefore, conservation effort in wild settings can be take into account in order for success in ensuring survival of tarsiers.

1. Classification of C. b. borneanus

Earlier in 2010, genus Tarsius was split to three in order to distinguish the differences between species, primarily in distribution, morphology, vocalizations, as well as, social structure. To date, there are three genera, which are Cephalopachus, Tarsius and Carlito, with a total number of 18 named species and subspecies belonging to these genera were classified in 2011. Genus Cephalopachus comprises of Western tarsiers, Eastern tarsiers are classified in genus Tarsius and Philippine tarsiers in genus Carlito (Endangered International Species Inc., 2011).

C. b. borneanus is a haplorrhine primate, which referring to its simple and dry nose, and eyes facing forward. It is classified as a subspecies of Western tarsier primarily due to its distribution throughout the Borneo Island, which is located at the west side among islands of the Southeast Asia. In comparison to Eastern tarsiers and Philippine tarsiers, C. b. borneanus or generally termed as Western tarsiers has the largest eyes, but the smallest ears, longest hind limbs and hands, as well as, intermediate tuft tails.

1. Distribution and Habitat

Tarsiers are restricted to the islands of Southeast Asia and are not reported its presence on mainland Asia. As species and subspecies of tarsiers are classified according to their distribution throughout these islands, Philippine tarsiers present on Sumatra, Mindanao, Samar and Selayar islands, Eastern tarsiers on Sulawesi and surrounding islands, whereas, Western tarsiers present on Borneo Island (Endangered International Species Inc., 2011).

C. b. borneanus can only be found from lowland areas to lower montane areas throughout the Borneo Island, including Sabah, Sarawak, Brunei and West Kalimantan. It habitat ranges from dense forests to thick scrublands and some types of agricultural land. As an arboreal animal, it clings to the trees at about 2 to 3 meters from the ground for protection against ground-based predators and for [pic 1]intercepting preys.

[pic 2]

1. Morphology of C. b. borneanus

In comparison to Philippine tarsiers and Eastern tarsiers, Western tarsiers, particularly of subspecies C. b. borneanus, have the largest eyes, but the smallest ears, longest hind limbs and hands, and intermediate tuft tails.

Its large eyes are crucial for good night vision since it is a nocturnal animal that awakes before sunset and up until before sunrise. Its bat-like ears are very sensitive to even the slightest sound around it. It also has unique spinal morphology, in which its head is able to turn 180 in each direction to cover the whole area around it. Due to that, tarsiers remain motionlessly clinging to branches of the trees, which benefit them to vigilantly prey for food and to become less vulnerable to their predators. Its longest hind limbs are adapted for leaping and enable them to jump distances about 5 meters. In addition to its longest limbs, tarsiers also featured with long anklebones namely the tarsals that aid in its locomotion. Its thin fingers bear adhesive or sticky pads on the tips purposely to capture preys. Tarsiers have soft and sleek fur with color ranges from mainly brown and some are beige and grey in color. These colors are useful for tarsiers to camouflage among the branches. Unique features of tarsiers make these primates are very good in picking up signs from their preys and predators (Gron, 2010; Endangered International Species Inc., 2011; Wildscreen, 2015).[pic 3]

[pic 4]

[pic 5]

1. Behavior of C. b. borneanus

1. Locomotion

Tarsiers are known to be a vertical clinger and leaper. The elongated tarsus aided the species in leaping as well as the fused fibula and tibia on the lower third part going towards the foot. Tarsiers however would rest, sleep, or remain stationary on vertical tree trunks. Its tail act as a support for when they resting at the tree trunks.

This species uses five main modes of locomotion (Flannery, 2007):

[pic 6]