| Western tarsier[1] | |
|---|---|
 | |
| C. bancanus inBorneo. Note theeyeshine. | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Family: | Tarsiidae |
| Genus: | Cephalopachus Swainson, 1835 |
| Species: | C. bancanus |
| Binomial name | |
| Cephalopachus bancanus (Horsfield, 1821) | |
 | |
| Western tarsier range | |
| Synonyms | |
Horsfield's tarsier (Cephalopachus bancanus) is theonly species oftarsier in the genusCephalopachus. Named by AmericannaturalistThomas Horsfield, it is also referred to aswestern tarsier. The species occurs onBorneo,Sumatra and nearby islands and is, like other members of the group, entirely nocturnal.
Although Horsfield's tarsier was usually placed in the genusTarsius with all other living tarsiers, it is quite distinct from thePhilippine tarsier and the various tarsiers ofSulawesi and nearby islands; therefore, scientists have placed it in a separate genus,Cephalopachus.[4]
The taxonomy of this species is in doubt, with some subspecies considered unsure.[5] In fact, over 20 years few studies have been done onC. bancanus and a taxonomic revision based upon intensive and systematic field surveys is overdue. TheIUCN believes that these subspecies should be treated as distinct and named as separate taxa until more definitive evidence is available.[6] When splitting the species into its own genus,Colin Groves and Myron Shekelle recognized thenatunensis population as a distinct subspecies.[4]
There are four recognized subspecies of Horsfield's tarsier:
Horsfield's tarsier is found in SouthernSumatra,Borneo andnearby islands.[7][page needed] The Bornean subspecies,C. b. borneanus, is known from manylowland sites inSabah,Brunei,Sarawak andWest Kalimantan and above 900 m (3,000 ft) in theKelabit uplands in northernSarawak. Other records show it fromKutai and Peleben inEast Kalimantan and Tanjung Maruwe inCentral Kalimantan.[7] This species can live in bothprimary andsecondary forests, and it also lives in forests along the coasts or on the edge ofplantations.[8]
Thepelage coloration ranges from pale-olive or reddish brown to pale or dark grey-brown, possibly varying with age. Based on 12 collected specimens,[7] the head to body measurement range from 121–154 mm (4.8–6.1 in). Horsfield's tarsier has an extremely long tail which can reach 181 to 224 mm (7.1 to 8.8 in) and is hairless except for tufts of hair at the end.[9] This species has twogrooming claws on each foot. The fingers are very long and have pads on the tips. The toes have flattenednails except for the second and third toes on hind feet, which bear claw-like nails.[7] It has large eyes which do not reflect light.[inconsistent] The membranous ears are slender and almost bare. Themolars of this species have high-cusps and are almosttritubercular.[10] 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.[11]
Horsfield's tarsier is anocturnal species. It sleeps alone during the day in a tangle ofvines orlianas at a height of 3.5 to 5 metres (11 to 16 ft).[12] This species prefers to sleep, rest, or remain stationary on perches that are angled 5 degrees from the vertical tree trunks, 1 to 4 cm (0.39 to 1.57 in) in diameter,[13] and it sleeps solitarily.[14] 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.[8] Horsfield's tarsier can be found from ground level up to a height of 7 m (23 ft) or more in the understory.[7]
This species iscarnivorous. It mainly eatsarthropods such asbeetles,orthopterans likegrasshoppers,katydids, andcrickets,butterflies,moths,cockroaches,praying mantis,ants,phasmids,cicadas,dragonflies,freshwater crabs, andspiders,[8][15] but also will eat smallvertebrates such asflying frogs,[15] bats (Chiroptera) including members of the genusTaphozous, the lesser short-nosed fruit bat (Cynopterus brachyotis), and the spotted-winged fruit bat (Balionycteris maculata), and snakes, of whichvenomous snakes have been found to be consumed, such as theelapidCalliophis intestinalis. This species was also found to consumebirds, includingspiderhunters,warblers,kingfishers, andpittas. It locates prey primarily by sound and catches the prey with its hands when foraging. Prey is killed through bites to theback of the neck[8] and the tarsier's eyes are shut when attacking.[16] It will consume the prey starting with the head and working its way down the body.[8] This speciesgets water both by drinking from a pool or stream, and by licking drops frombamboo leaves or from water running down the trunks of trees.[17] Horsfield's tarsier is a host of theacanthocephalan intestinal parasiteMoniliformis tarsii.[18]
Like all tarsiers, Horsfield's tarsiers are vertical clingers andleapers, 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.[13] Other modes of locomotion used by the species includeclimbing, quadrupedal walking, hopping and "cantilevering."[12][15]
Horsfield's tarsiers aremonogamous, with a copulation frequency duringestrus of once per night.[19]Courtshipcalls are performed by the male and he emits 2–3 chirrups while opening and closing the mouth.[19] 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.[19] If the female is not in estrus, she will emit anagonistic call which is often followed by biting and pushing the male away.[19] Both sexes' calls last on average for 1 second, and the interval between calls is on average 3 seconds.[19]
Infants are born with their eyes open and fully furred and able to groom themselves.[20] The mother will carry her infant in her mouth and when she forages for food the mother will park the infant on a branch.[21] Infant sounds are mostly clicks: "k", "tk", "ki", or a rapid "kooih"[22] and can be heard when the infant is left alone or is cold.[22] 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.[20]Social grooming in this species only occurs between mothers and infants,[23] removing dead skin andparasites 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.[23]
Young leave their mother's range at the onset ofpuberty, and find their ownterritory.[20] 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.[19]
The rapid loss of habitat due toforest conversion,oil palm plantations,fire, andlogging is cause for concern.[24] Additionally, the species is also collected for theillegal pet trade and wrongly considered apest to agricultural crops. It can suffer, directly and indirectly, from the use of agriculturalpesticides.
Horsfield's tarsier is listed asvulnerable in the 2008 IUCN Red List of Threatened Species,[2] listed inCITES Appendix II, and protected by law in Indonesia and in Malaysia.
In February 2007, the governments ofBrunei,Malaysia, andIndonesia agreed to protect roughly 220,000 km2 (85,000 sq mi) of tropical forest in the "Heart of Borneo" region. Environmental groupWWF was particularly active in the establishment of the protected area.[25] 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.[26]
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