{{Short description|Species of primate}} {{Speciesbox | name = Western tarsier<ref name=msw3>{{MSW3 Groves|pages=127|id=12100167}}</ref> | image = Western Tarsier.jpg | image_caption = ''C. bancanus'' in Borneo. Note the eyeshine. | status = VU | status_system = IUCN3.1 | status_ref = <ref name="iucn status 13 November 2021">{{cite iucn |author=Shekelle, M. |author2=Yustian, I. |date=2020 |title=''Cephalopachus bancanus'' |volume=2020 |article-number=e.T21488A17976989 |doi=10.2305/IUCN.UK.2020-3.RLTS.T21488A17976989.en |access-date=13 November 2021}}</ref> | parent_authority = Swainson, 1835 | taxon = Cephalopachus bancanus | authority = (Horsfield, 1821) | synonyms = * ''Tarsius bancanus'' <small>Horsfield, 1821</small><ref>{{cite book |last=Schlitter |first= D.A. |editor-last1=Wilson |editor-first1=D.E. |editor-last2=Reeder |editor-first2= D.M. |year=2005 |title=Mammal Species of the World |url=https://books.google.com/books?id=JgAMbNSt8ikC&q=Tarsius+Bancanus |edition=4-th |location=Baltimore, Maryland, USA |publisher=Johns Hopkins University Press |page=127 |isbn=978-0-8018-8221-0 }}</ref> | range_map = Horsfield's Tarsier area.png | range_map_caption = Western tarsier range }} '''Horsfield's tarsier''' ('''''Cephalopachus bancanus''''') is the only species of tarsier in the genus '''''Cephalopachus'''''. Named by American naturalist 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.
==Taxonomy== Although Horsfield's tarsier was usually placed in the genus ''Tarsius'' with all other living tarsiers, it is quite distinct from the Philippine tarsier and the various tarsiers of Sulawesi and nearby islands; therefore, scientists have placed it in a separate genus, ''Cephalopachus''.<ref name=2010_Groves_Shekelle>{{cite journal | last1 = Groves | first1 = C. | last2 = Shekelle | first2 = M. | title = The Genera and Species of Tarsiidae | journal = International Journal of Primatology | volume = 31 | pages = 1071–1082 | year = 2010 | issue = 6 | doi = 10.1007/s10764-010-9443-1| s2cid = 21220811 }}</ref>
The taxonomy of this species is in doubt, with some subspecies considered unsure.<ref>{{cite journal | doi = 10.1023/B:IJOP.0000014647.18720.32 | author = Brandon-Jones, D. | author2 = Eudey, A.A. | author3 = Geissmann, T. | author4 = Groves, C.P. | author5 = Melnick D.J., Morales | author6 = J.C., Shekelle, M. | author7 = Stewart, C.B | name-list-style = amp | year = 2004 | title = Asian Primate Classification | journal = International Journal of Primatology | volume = 25 | issue = 1 | pages = 97–164| s2cid = 29045930 }}</ref> 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.<ref>{{cite iucn |author=Shekelle, M. |author2=Yustian, I. |date=2021 |title=''Cephalopachus bancanus'' ssp. ''bancanus'' |volume=2021 |article-number=e.T39762A17992163 |doi=10.2305/IUCN.UK.2021-1.RLTS.T39762A17992163.en |access-date=13 November 2021}}</ref> When splitting the species into its own genus, Colin Groves and Myron Shekelle recognized the ''natunensis'' population as a distinct subspecies.<ref name=2010_Groves_Shekelle/>
There are four recognized subspecies of Horsfield's tarsier: * ''Cephalopachus bancanus bancanus'' — Bangka Island tarsier * ''Cephalopachus bancanus saltator'' — Belitung Island tarsier * ''Cephalopachus bancanus borneanus'' — Bornean tarsier * ''Cephalopachus bancanus natunensis'' — Natuna Islands tarsier
==Habitat and distribution==
Horsfield's tarsier is found in Southern Sumatra, Borneo and nearby islands.<ref name=field/>{{pn |date=October 2025}} The Bornean subspecies, ''C. b. borneanus'', is known from many lowland sites in Sabah, Brunei, Sarawak and West Kalimantan and above {{convert|900|m|abbr=on}} in the Kelabit uplands in northern Sarawak. Other records show it from Kutai and Peleben in East Kalimantan and Tanjung Maruwe in Central Kalimantan.<ref name="field" /> This species can live in both primary and secondary forests, and it also lives in forests along the coasts or on the edge of plantations.<ref name=Niemitz1979/>
==Physical description== <!--What differentiates this genus from ''Tarsius''? What are its diagnostic traits?--> 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,<ref name=field>{{cite book | author = Payne, J. | author2 = Francis, C. M. | author3 = Phillipps, K | name-list-style = amp | year = 1994 | title = A Field guide to the Mammals of Borneo | location = Petaling Jaya | publisher = The Sabah Society}}</ref> the head to body measurement range from {{convert|121|–|154|mm|abbr=on}}. Horsfield's tarsier has an extremely long tail which can reach {{convert|181|to|224|mm|abbr=on}} and is hairless except for tufts of hair at the end.<ref name=Sussman>{{cite book | author = Sussman, R.W | year = 1999 | title = Primate Ecology and Social Structure: Vol. 1 Lorises, Lemurs and Tarsiers | publisher = Pearson Custom Publishing}}</ref> This species has two grooming claws 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.<ref name=field/> It has large eyes which do not reflect light.{{Inconsistent|reason=The Infobox Image}} The membranous ears are slender and almost bare. The molars of this species have high-cusps and are almost tritubercular.<ref name=food>{{cite journal | author = Crompton, R.H. | author2 = Savage, R. | author3 = Spears, I.R | name-list-style = amp | year = 1998 | title = The mechanics of food reduction in Tarsius bancanus: Hard-object feeder, soft-object feeder or both? | journal = Folia Primatologica | volume = 69 | issue = suppl 1 | pages = 41–59 | doi=10.1159/000052698| pmid = 9595687 | s2cid = 24464173 }}</ref> 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.<ref name=Nowak>{{cite book | author = Nowak, R.M | year = 1999 | title = Walker's Primates of the World | publisher = Johns Hopkins University Press | location = Baltimore | isbn = 0-8018-6251-5 | url-access = registration | url = https://archive.org/details/walkersprimateso0000nowa }}</ref>
==Biology== Horsfield's tarsiers are nocturnal, sleeping alone during the day in a tangle of vines or lianas at a height of {{convert|3.5|to|5|m}}.<ref name=Crompton1986>{{cite journal | doi = 10.1007/BF02382075 |author1=Crompton, R.H. |author2=Andau, P.M | year = 1986 | title = Locomotion and Habitat Utilization in Free-ranging Tarsius bancanus: A Preliminary Report | journal = Primates | volume = 27 | issue = 3 | pages = 337–355|s2cid=25836867 }}</ref> This species prefers to sleep, rest, or remain stationary on perches that are angled 5 degrees from the vertical tree trunks, {{convert|1|to|4|cm|abbr=on}} in diameter,<ref name=Niemitz1984a>{{cite book | author = Niemitz, C |author-link=Carsten Niemitz| year = 1984a | chapter = Locomotion and posture of Tarsius bancanus | title = Biology of Tarsiers | editor = C. Niemitz |editor-link=Carsten Niemitz | publisher = Gustav Fischer Verlag | location = Stuttgart | isbn = 0-89574-182-2}}</ref> and it sleeps solitarily.<ref name=Crompton1987>{{cite journal | doi = 10.1007/BF02737113 |author1=Crompton, R.H. |author2=Andau, P.M | year = 1987 | title = Ranging, activity rhythms, and sociality in free-ranging Tarsius bancanus: A preliminary report | journal = International Journal of Primatology | volume = 8 | issue = 1 | pages = 43–71|s2cid=39920648 }}</ref> 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.<ref name=Niemitz1979>{{cite book | author = Niemitz, C. |author-link=Carsten Niemitz | year = 1979 | chapter = Outline of the behavior of Tarsius bancanus | title = The Study of Prosimian Behavior |editor1=G.A. Doyle |editor2=R.D. Martin | publisher = Academic Press | location = New York}}</ref> Horsfield's tarsier can be found from ground level up to a height of {{convert|7|m|abbr=on}} or more in the understory.<ref name = field/> thumb|right|''Calliophis intestinalis'' is preyed on by the western tarsier This species is carnivorous. It mainly eats arthropods such as beetles, orthopterans like grasshoppers, katydids, and crickets, butterflies, moths, cockroaches, praying mantis, ants, phasmids, cicadas, dragonflies, freshwater crabs, and spiders,<ref name=Niemitz1979/><ref name="Crompton2010">{{cite journal |last1=Crompton |first1=Robin Huw |last2=Blanchard |first2=Mary L. |last3=Coward |first3=Sam |last4=Alexander |first4=R. Mcneill |last5=Thorpe |first5=Susannah K. |title=Vertical Clinging and Leaping Revisited: Locomotion and Habitat Use in the Western Tarsier, Tarsius bancanus Explored Via Loglinear Modeling |journal=International Journal of Primatology |date=2010 |volume=31 |issue=6 |pages=958–979 |doi=10.1007/s10764-010-9420-8 |url=https://link.springer.com/article/10.1007/s10764-010-9420-8 |access-date=21 November 2024|url-access=subscription }}</ref> but also will eat small vertebrates such as flying frogs,<ref name="Crompton2010" /> 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 venomous snakes have been found to be consumed, such as the elapid ''Calliophis intestinalis''. This species was also found to consume birds, including spiderhunters, warblers, kingfishers, and pittas. It locates prey primarily by sound and catches the prey with its hands when foraging. Prey is killed through bites to the back of the neck<ref name=Niemitz1979/> and the tarsier's eyes are shut when attacking.<ref name=Fogden>{{cite book | author = Fogden, M.P.L | year = 1974 | chapter = A preliminary field study of the western tarsier, Tarsius bancanus Horsefield | title = Prosimian Biology |editor1=R.D. Martin |editor2=G.A. Doyle |editor3=A.C. Walker | publisher = University of Pittsburgh Press | location = Pittsburgh}}</ref> It will consume the prey starting with the head and working its way down the body.<ref name=Niemitz1979/> This species gets water both by drinking from a pool or stream, and by licking drops from bamboo leaves or from water running down the trunks of trees.<ref name = Niemitz1984>{{cite book | author = Niemitz, C |author-link=Carsten Niemitz | year = 1984d | chapter = Synecological relationships and feeding behaviour of the genus Tarsius | title = Biology of Tarsiers | editor = C. Niemitz |editor-link=Carsten Niemitz | publisher = Gustav Fischer Verlag | location = Stuttgart | isbn = 0-89574-182-2}}</ref> Horsfield's tarsier is a host of the acanthocephalan intestinal parasite ''Moniliformis tarsii''.<ref name="Deveaux1988">{{Cite journal |doi = 10.2307/3282462|pmid = 3128654|jstor = 3282462|title = Two New Species of Moniliformis (Acanthocephala: Moniliformidae) from Malaysia|journal = The Journal of Parasitology|volume = 74|issue = 2|pages = 322–5|year = 1988|last1 = Deveaux|first1 = Timothy P.|last2 = Schmidt|first2 = Gerald D.|last3 = Krishnasamy|first3 = M.}}</ref>
Like all tarsiers, Horsfield's tarsiers are vertical clingers and leapers, 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.<ref name=Niemitz1984a/> Other modes of locomotion used by the species include climbing, quadrupedal walking, hopping and "cantilevering."<ref name=Crompton1986/><ref name="Crompton2010" />
===Life cycle=== Horsfield's tarsiers are monogamous, with a copulation frequency during estrus of once per night.<ref name=Wright1986a/> Courtship calls are performed by the male and he emits 2–3 chirrups while opening and closing the mouth.<ref name=Wright1986a/> 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.<ref name=Wright1986a>{{cite journal | author = Wright, P.C. | author2 = Toyama, L.M. | author3 = Simons, E.L | name-list-style = amp | year = 1986 | title = Courtship and Copulation in Tarsius bancanus | journal = Folia Primatologica | volume = 46 | issue = 3 | pages = 142–148 | pmid=3100401 | doi=10.1159/000156247}}</ref> If the female is not in estrus, she will emit an agonistic call which is often followed by biting and pushing the male away.<ref name=Wright1986a/> Both sexes' calls last on average for 1 second, and the interval between calls is on average 3 seconds.<ref name=Wright1986a/>
Infants are born with their eyes open and fully furred and able to groom themselves.<ref name=Robert1994>{{cite journal | doi = 10.1007/BF02735232 | author = Roberts, M | year = 1994 | title = Growth, development, and parental care in the Western tarsier (Tarsius bancanus) in captivity: Evidence for a "slow" life-history and nonmonogamous mating system | journal = International Journal of Primatology | volume = 15 | issue = 1 | pages = 1–28| s2cid = 7462413 }}</ref> The mother will carry her infant in her mouth and when she forages for food the mother will park the infant on a branch.<ref name=Haring>{{cite journal | author = Haring, D.M. | author2 = Wright, P.C. | author3 = Simons, E.L | name-list-style = amp | year = 1985 | title = Social behaviors of Tarsius syrichta and Tarsius bancanus | journal = American Journal of Physical Anthropology | volume = 66 | page = 179|doi= 10.1002/ajpa.1330660204}}</ref> Infant sounds are mostly clicks: "k", "tk", "ki", or a rapid "kooih"<ref name=Niemitz1984b>{{cite book | author = Niemitz, C |author-link=Carsten Niemitz | year = 1984b | chapter = Vocal communication of two tarsier species (Tarsius bancanus and Tarsius spectrum) | title = Biology of Tarsiers | editor = C. Niemitz |editor-link=Carsten Niemitz | publisher = Gustav Fischer Verlag | location = Stuttgart | isbn = 0-89574-182-2}}</ref> and can be heard when the infant is left alone or is cold.<ref name=Niemitz1984b/> 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.<ref name=Robert1994/> Social grooming in this species only occurs between mothers and infants,<ref name=Niemitz1984c>{{cite book | author = Niemitz, C |author-link=Carsten Niemitz | year = 1984c | chapter = An investigation and review of the territorial behaviour and social organisation of the genus Tarsius | title = Biology of Tarsiers | editor = C. Niemitz |editor-link=Carsten Niemitz | publisher = Gustav Fischer Verlag | location = Stuttgart | isbn = 0-89574-182-2}}</ref> removing dead skin and parasites 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.<ref name=Niemitz1984c/>
Young leave their mother's range at the onset of puberty, and find their own territory.<ref name=Robert1994/> 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.<ref name=Wright1986a/>
==Conservation status== thumb|right|150px|upright|Horsfield's tarsier in Sarawak, wearing a metal collar. The rapid loss of habitat due to forest conversion, oil palm plantations, fire, and logging is cause for concern.<ref>{{cite journal | author = Yustian, I. | author2 = Merker, S. | author3 = Supriatna, J | name-list-style = amp | year = 2008 | title = RELATIVE POPULATION DENSITY OF Tarsius dianae IN MAN-INFLUENCED HABITATS | journal = Asian Primates Journal | volume = 1 | issue = 1}}</ref> 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 pesticides.
Horsfield's tarsier is listed as vulnerable in the 2008 IUCN Red List of Threatened Species,<ref name="iucn status 13 November 2021" /> 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 {{convert|220,000|km2|sqmi|abbr=on}} of tropical forest in the "Heart of Borneo" region. Environmental group WWF was particularly active in the establishment of the protected area.<ref>{{cite web | author = Butler, R. A | year = 2006 | title = Borneo | access-date = January 27, 2009 | url = http://www.mongabay.com/borneo.html}}</ref> 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.<ref>World Wildlife Fund. (2007). Resolution concerning the 'Heart of Borneo'. Association for Tropical Biology and Conservation.</ref>
==Gallery== <gallery class="center" mode="nolines" widths="250" noborder="no"> File:Tarsier - Tarsius tarsius - NHMI.jpg|''Cephalopachus bancanus bancanus'' from Bangka in National Museum of Ireland, Dublin File:Tarsius di Belitung 06.jpg|''Cephalopachus bancanus saltator'' from Belitung File:Bornean Tarsier (Cephalopachus bancanus borneanus) (8067063777).jpg|''Cephalopachus bancanus borneanus'' File:Stamp of Indonesia - 2010 - Colnect 248262 - Belitung Island Tarsier Tarsius bancanus saltator.jpeg|Postage stamp File:Sofyan Efendi Tarsius Mencari Mangsa DSC 0837.jpg File:Stamp of Sarawak - 1950 - Colnect 306198 - Western Tarsier Cephalopachus bancanus.jpeg|Postage stamp featuring the western tarsier and George VI (top left) File:Tarsius Fransiskus Simbolon.jpg File:Cephalopachus bancanus borneanus 49161649.jpg|In darkness </gallery>
==References== {{Wikispecies|Tarsius bancanus}} {{Commons category|Cephalopachus bancanus}} {{Reflist|25em}}
{{Tarsiidae nav}} {{Haplorhini|Ha.}} {{Taxonbar|from1=Q14518750|from2=Q22113538|from3=Q846009}}
Category:Tarsiers Category:Primates of Indonesia Category:Primates of Borneo Category:Mammals of Brunei Category:Mammals of Malaysia Category:Vulnerable fauna of Asia Category:Mammals described in 1821 Category:Taxa named by Thomas Horsfield Category:Arboreal mammals