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Horsfeld's tarsier ( Cephalopachus bancanus) is the Monotypic taxon of tarsier in the genus Cephalopachus. Named by American Natural history Thomas Horsfield, it is also referred to as western tarsier. The species occurs on Borneo, Sumatra and nearby islands and is, like other members of the group, entirely nocturnal.
The taxonomy of this species is in doubt, with some subspecies considered unsure. In fact, over 20 years few studies have been done on C. bancanus and a taxonomic revision based upon intensive and systematic field surveys is overdue. The IUCN believes that these subspecies should be treated as distinct and named as separate taxa until more definitive evidence is available. When splitting the species into its own genus, Colin Groves and Myron Shekelle recognized the natunensis population as a distinct subspecies.
There are four recognized subspecies of Horsfeld's tarsier:
Like all tarsiers, Horsfield's tarsiers are vertical clingers and Jumping, known for extraordinary leaping abilities. An individual will mainly support itself with its feet and the tail, both exerting enough force to hold the individual in place. The hands are not always used because of the pads located on the feet provide adequate grip. The hands are usually placed no higher than its nose except when resting; the hands are only placed higher up to maintain the position of the individual. Other modes of locomotion used by the species include climbing, quadrupedal walking, hopping and "."
Horsfield's tarsiers are monogamous, with a copulation frequency during Estrous cycle of once per night. Courtship calls are performed by the male and he emits 2–3 chirrups while opening and closing the mouth. This call happens within 5 minutes of looking at the female. Once the male gives his courtship call, if the female is receptive, she will perform genital displays to him. If the female is not in estrus, she will emit an agonistic call which is often followed by biting and pushing the male away. Both sexes' calls last on average for 1 second, and the interval between calls is on average 3 seconds.
Infants are born with their eyes open and fully furred and able to groom themselves. The mother will carry her infant in her mouth and when she forages for food the mother will park the infant on a branch. Infant sounds are mostly clicks: "k", "tk", "ki", or a rapid "kooih" and can be heard when the infant is left alone or is cold. The mother stays in contact with their infants using high-pitched calls. Infants were found to first use the tails as support during resting at 7–10 days.
Social grooming in this species only occurs between mothers and infants, removing dead skin and Ectoparasite by scratching with their toe claws and licking their fur, avoiding their faces. Faces are cleaned by rubbing on branches and it is to reinforce social bonds.
Young leave their mother's range at the onset of puberty, and find their own territory. Horsfield's tarsiers mark their territory with scents from urine and glandular secretions on a substrate while scratching the surface with its hind-limb toe claws.
Horsfield's tarsier is listed as vulnerable in the 2008 IUCN Red List of Threatened Species, listed in CITES Appendix II, and protected by law in Indonesia and in Malaysia.
In February 2007, the governments of Brunei, Malaysia, and Indonesia agreed to protect roughly of tropical forest in the "Heart of Borneo" region. Environmental group WWF was particularly active in the establishment of the protected area. In the "Heart of Borneo" project, non-governmental organizations (NGOs) have played a role in promoting the critical initiative and in assisting the neighboring nations in its conceptualization, design, and implementation. The countries are to improve biodiversity conservation in Bornean production forests, and to ensure that such forests are not simply converted to agricultural land-uses such as oil-palm plantations after logging.World Wildlife Fund. (2007). Resolution concerning the ‘Heart of Borneo’. Association for Tropical Biology and Conservation.
Habitat and distribution
Horsfield's tarsier is found in Southern Sumatra, Borneo and nearby islands. The Bornean subspecies, C. b. borneanus, is known from many lowland sites in Sabah, Brunei, Sarawak and West Kalimantan and above in the Kelabit uplands in Northern Sarawak. Other records show it from Kutai and Peleben in East Kalimantan and Tanjung Maruwe in Central Kalimantan. This species can live in both primary forest and , and it also lives in forests along the coasts or on the edge of .
Physical description
The pelage coloration ranges from pale-olive or reddish brown to pale or dark grey-brown, possibly varying with age. Based on 12 collected specimens, the head to body measurement range from . Horsfield's tarsier has an extremely long tail which can reach and is hairless except for tufts of hair at the end. This species has two on each foot. The fingers are very long and have pads on the tips. The toes have flattened nails except for the second and third toes on hind feet, which bear claw-like nails. It has large eyes which do not reflect light. The membranous ears are slender and almost bare. The molars of this species have high-cusps and are almost . The dental formula of Horsfield's tarsier is 2:1:3:3 on the upper jaw and 1:1:3:3 on the lower jaw.
Behaviour and ecology
Horsfield's tarsier is a nocturnal species. It sleeps alone during the day in a tangle of or at a height of . This species prefers to sleep, rest, or remain stationary on perches that are angled 5 degrees from the vertical tree trunks, in diameter, and it sleeps solitarily. Before sunset, Horsfield's tarsier will wake up and wait 10 to 20 minutes before moving around the understory and spending 1.5 to 2 hours of the night foraging for food. Horsfield's tarsier can be found from ground level up to a height of or more in the understory.
This species is carnivorous. It mainly eats such as , like , katydids, and crickets, butterflies, , , praying mantis, , Phasmatodea, , dragonflies, , and , but also will eat small vertebrates such as , bats (Chiroptera) including members of the genus Taphozous, the lesser short-nosed fruit bat ( Cynopterus brachyotis), and the spotted-winged fruit bat ( Balionycteris maculata), and snakes, of which have been found to be consumed, such as the Elapidae Calliophis intestinalis. This species was also found to consume , including , , , and . It locates prey primarily by sound and catches the prey with its hands when foraging. Prey is killed through bites to the nape and the tarsier's eyes are shut when attacking. It will consume the prey starting with the head and working its way down the body. This species Drinking both by drinking from a pool or stream, and by licking drops from bamboo leaves or from water running down the trunks of trees. Horsfield's tarsier is a host of the intestinal parasite Moniliformis tarsii.
Conservation status
The rapid loss of habitat due to forest conversion, Palm oil, Wildfire, and logging is cause for concern. Additionally, the species is also collected for the illegal pet trade and wrongly considered a pest to agricultural crops. It can suffer, directly and indirectly, from the use of agricultural .
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