Tarsier

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Tarsiers[1][2]
Temporal range: 45–0Ma
Late Eocene to Recent
Tarsier-GG.jpg
Philippine tarsier (Carlito syrichta)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorrhini
Infraorder: Tarsiiformes
Family: Tarsiidae
Gray, 1825
Type genus
Tarsius
Genera

Carlito
Cephalopachus
Tarsius

Tarsiers are haplorrhine primates of the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes. Although the group was once more widespread, all the species living today are found in the islands of Southeast Asia.

Evolutionary history[edit]

Fossil record[edit]

Fossils of tarsiiform primates are found in Asia, Europe, and North America, with disputed fossils from Africa, but extant tarsiers are restricted to several Southeast Asian islands, including the Philippines, Sulawesi, Borneo, and Sumatra. The fossil record indicates their dentition has not changed much, except in size, in the past 45 million years.

Within the family Tarsiidae, there are two extinct genera, Xanthorhysis and Afrotarsius. However, the placement of Afrotarsius is not certain,[3] and it is sometimes listed in its own family, Afrotarsiidae, within the infraorder Tarsiiformes,[4] or considered an anthropoid primate.[5]

So far, three fossil species of the genus Tarsius are known from the fossil record:

The genus Tarsius has a longer fossil record than any other primate genus, but the assignment of the Eocene and Miocene fossils to the genus is questionable.[8]

Classification[edit]

The phylogenetic position of extant tarsiers within the order Primates has been debated for much of the past century, and tarsiers have alternately been classified with strepsirrhine primates in the suborder Prosimii, or as the sister group to the simians (=Anthropoidea) in the infraorder Haplorrhini. Analysis of SINE insertions, a type of macromutation to the DNA, is argued to offer very persuasive evidence for the monophyly of Haplorrhini, where other lines of evidence, such as DNA sequence data, remain ambiguous. Thus, some systematists argue the debate is conclusively settled in favor of a monophyletic Haplorrhini. In common with simians, tarsiers have a mutation in the L-gulonolactone oxidase (GULO) gene, which confers the need for vitamin C in the diet. Since the strepsirrhines do not have this mutation and have retained the ability to make vitamin C, the genetic trait that confers the need for it in the diet would tend to place tarsiers with haplorrhines.[9]

Philippine tarsier (Carlito syrichta), one of the smallest primates.

At a lower phylogenetic level, the tarsiers have, until recently, all been placed in the genus Tarsius,[1] while it was debated whether the species should be placed in two (a Sulawesi and a Philippine-western group) or three separate genera (Sulawesi, Philippine and western groups).[10] Species level taxonomy is complex, with morphology often being of limited use compared to vocalizations.[citation needed] Further confusion existed over the validity of certain names. Among others, the widely used T. dianae has been shown to be a junior synonym of T. dentatus, and comparably, T. spectrum is now considered a junior synonym of T. tarsier.[1]

In 2010, Colin Groves and Myron Shekelle suggested splitting the genus Tarsius into three genera, the Philippine tarsiers (genus Carlito), the western tarsiers (genus Cephalopachus), and the eastern tarsiers (genus Tarsius). This was based on differences in dentition, eye size, limb and hand length, tail tufts, tail sitting pads, the number of mammae, chromosome count, socioecology, vocalizations, and distribution. The senior taxon of the species, T. tarsier was restricted to the population of a Selayar island, which then required the resurrection of the defunct taxon T. fuscus. Their classification, which includes several newly described species, is as follows:[2]

Anatomy and physiology[edit]

Tarsier tree climbing

Tarsiers are small animals with enormous eyes; each eyeball is approximately 16 mm in diameter and is as large as its entire brain.[11] The unique cranial anatomy of the tarsier results from the need to balance their large eyes and heavy head so they are able to wait silently for nutritious prey.[12] Tarsiers have an incredibly strong auditory sense because their auditory cortex is very distinct.[12] Tarsiers also have very long hind limbs, due mostly to the extremely elongated tarsus bones of the feet, from which the animals get their name. The combination of their elongated tarsi and fused tibiofibulae makes them morphologically specialized for vertical clinging and leaping.[13] The head and body range from 10 to 15 cm in length, but the hind limbs are about twice this long (including the feet), and they also have a slender tail from 20 to 25 cm long. Their fingers are also elongated, with the third finger being about the same length as the upper arm. Most of the digits have nails, but the second and third toes of the hind feet bear claws instead, which are used for grooming. Tarsiers have very soft, velvety fur, which is generally buff, beige, or ochre in color.[14]

Unlike other prosimians, tarsiers lack any toothcomb, and their dental formula is also unique:2.1.3.31.1.3.3

Unlike many nocturnal vertebrates, tarsiers lack a light-reflecting area (tapetum lucidum) of the eye and have a fovea.

The tarsier's brain is different from other primates in terms of the arrangement of the connections between the two eyes and the lateral geniculate nucleus, which is the main region of the thalamus that receives visual information. The sequence of cellular layers receiving information from the ipsilateral (same side of the head) and contralateral (opposite side of the head) eyes in the lateral geniculate nucleus distinguishes tarsiers from lemurs, lorises, and monkeys, which are all similar in this respect.[15] Some neuroscientists suggested that "this apparent difference distinguishes tarsiers from all other primates, reinforcing the view that they arose in an early, independent line of primate evolution."[16]

Philippine tarsiers are capable of hearing frequencies as high as 91 kHz. They are also capable of vocalizations with a dominant frequency of 70 kHz.[17]

Behavior[edit]

Tarsiers are the only extant entirely carnivorous primates: they are primarily insectivorous, and catch insects by jumping at them. They are also known to prey on birds, snakes, lizards, and bats.[14]

Pygmy tarsiers differ from other species of tarsiers in terms of their morphology, communication, and behavior.[18] The differences in morphology that distinguish pygmy tarsiers from other species of tarsiers are likely based on their high altitude environment.[19]

All tarsier species are nocturnal in their habits, but like many nocturnal organisms, some individuals may show more or less activity during the daytime. Based on the anatomy of all tarsiers, they are all adapted for leaping even though they all vary based on their species.[20][21]

Ecological variation is responsible for differences in morphology and behavior in tarsiers because different species become adapted to local conditions based on the level of altitude.[22] For example, the colder climate at higher elevations can influence cranial morphology.[23]

Gestation takes about six months,[24] and tarsiers give birth to single offspring. Young tarsiers are born furred, and with open eyes, and are able to climb within a day of birth. They reach sexual maturity by the end of their second year. Sociality and mating system varies, with tarsiers from Sulawesi living in small family groups, while Philippine and western tarsiers are reported to sleep and forage alone.

Tarsiers tend to be extremely shy animals.[citation needed]

Conservation[edit]

Tarsiers have never formed successful breeding colonies in captivity. This may be partly due to their special feeding requirements.[25][26][27][28][29]

A sanctuary near the town of Corella, on the Philippine island of Bohol, is having some success restoring tarsier populations. The Philippines Tarsier Foundation (PTFI) has developed a large, semiwild enclosure known as the Tarsier Research and Development Center. Carlito Pizarras, also known as the "Tarsier man", founded this sanctuary where visitors can watch tarsiers up close in the wild (naturally without touching them). As of 2011, the sanctuary was taken care of by him and his brother.[citation needed] The trees in the sanctuary are populated with nocturnal insects that make up the tarsier's diet.[30]

The conservation status of all tarsiers is vulnerable to extinction. Tarsiers are a conservation dependent species meaning that they need to have more and improved management of protected habitats or they will definitely become extinct in the future.[12]

The 2008-described Siau Island tarsier is regarded as Critically Endangered and was listed among The World's 25 Most Endangered Primates by Conservation International and the IUCN/SCC Primate Specialist Group in 2008.[31] The Malaysian government protects tarsiers by listing them in the Totally Protected Animals of Sarawak, the Malaysian state in Borneo where they are commonly found.[32]

References[edit]

  1. ^ a b c Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 127–128. OCLC 62265494. ISBN 0-801-88221-4. 
  2. ^ a b Groves, C.; Shekelle, M. (2010). "The Genera and Species of Tarsiidae" (PDF). International Journal of Primatology 31 (6): 1071–1082. doi:10.1007/s10764-010-9443-1. 
  3. ^ a b c Gunnell, G.; Rose, K. (2002). "Tarsiiformes: Evolutionary History and Adaptation". In Hartwig, W.C. The Primate Fossil Record. Cambridge University Press. ISBN 0-521-66315-6. 
  4. ^ McKenna, M.C., and Bell, S.K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 337–340 pp. ISBN 0-231-11013-8
  5. ^ a b Chiamanee, Y., Lebrun, R., Yamee, C., and Jaeger, J.-J. (2010). "A new Middle Miocene tarsier from Thailand and the reconstruction of its orbital morphology using a geometric–morphometric method". Proceedings of the Royal Society B: Biological Sciences: –. doi:10.1098/rspb.2010.2062. 
  6. ^ Rossie, J.B.; Ni, X.; Beard, K.C. (2006). "Cranial remains of an Eocene tarsier" (PDF). PNAS 102 (12): 4381–4385. 
  7. ^ Nowak, R.M. (1999). Walker's Mammals of the World (6th ed.). Johns Hopkins University Press. pp. 94–97. ISBN 0-8018-5789-9. 
  8. ^ Simons, E.L. (2003). "The Fossil Record of Tarsier Evolution". In Wright, P.C.; Simons, E.L.; Gursky, S. Tarsiers: past, present, and future. ISBN 978-0-8135-3236-3. 
  9. ^ Pollock, J. I. & Mullin, R. J. (1986). "Vitamin C biosynthesis in prosimians: Evidence for the anthropoid affinity of Tarsius". American Journal of Physical Anthropology 73 (1): 65–70. doi:10.1002/ajpa.1330730106. PMID 3113259. 
  10. ^ Brandon-Jones, D.; et al. (2004). "Asian primate classification". International Journal of Primatology 25 (1): 97–164. doi:10.1023/B:IJOP.0000014647.18720.32. 
  11. ^ Shumaker, Robert W.; Benjamin B. Beck (2003). Primates in Question. Smithsonian Books. ISBN 1-58834-151-8. 
  12. ^ a b c Shekelle, Myron, and Gursky. (2010) "Why tarsiers? Why now? An introduction to the special edition on tarsiers." International Journal Of Primatology 31(6): 937-940. Academic Search Premier. Web. 18 Apr. 2013.
  13. ^ Rasmussen, D. T., Conroy, G. C., & Simons, E. L. (1998). Tarsier-like locomotor specializations in the Oligocene primate Afrotarsius. Proceedings of the National Academy of Sciences of the United States of America, 95, 14848–14850.
  14. ^ a b Niemitz, Carsten (1984). Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 338–339. ISBN 0-87196-871-1. 
  15. ^ Rosa, M. G.; Pettigrew J. D.; Cooper H. M. (1996). "Unusual pattern of retinogeniculate projections in the controversial primate Tarsius". Brain Behavior and Evolution 48 (3): 121–129. doi:10.1159/000113191. 
  16. ^ Collins, C. E.; Hendrickson, A.; Kaas, J. H. (2005). "Overview of the visual system of tarsius". The Anatomical Record Part A 287 (1): 1013–1025. doi:10.1002/ar.a.20263. PMID 16200648. 
  17. ^ Ramsier, Marissa A.; Cunningham A.J.; Moritz G.L.; Finneran J.J.; Williams C.V.; Ong P.S.; Gursky-Doyen S.L.; Dominy N.J. (2012). "Primate communication in the pure ultrasound". Biology Letters. doi:10.1098/rsbl.2011.1149. 
  18. ^ Grow, Nanda, and Sharon Gursky-Doyen. "Preliminary Data On The Behavior, Ecology, And Morphology Of Pygmy Tarsiers ( Tarsius Pumilus)." International Journal Of Primatology 31.6 (2010): 1174-1191. Academic Search Premier. Web. 18 Apr. 2013.
  19. ^ Musser, G. G., & Dagosto, M. (1987). The identity of Tarsius pumilus, a pygmy species endemic to the montane mossy forests of Central Sulawesi. American Museum Novitates, 2867, 1–53
  20. ^ Dagosto, M., Gebo, D. L., & Dolino, C. (2001). Positional behavior and social organization of the Philippine tarsier (Tarsius syrichta). Primates, 42, 233–243.
  21. ^ Niemitz, C. (1977). Zur funktionsmorphologie und biometrie der gattung Tarsius, Storr, 1780. Cour Forschung Institut Senckenberg, 25, 1–161. Niemitz, C. (1979). Relationships among anatomy, ecology, and behavior: A model developed in the genus Tarsius, with thoughts about phylogenetic mechanisms and adaptive interactions. In S. 1190 N. Grow, S. Gursky-DoyenMorbeck, H. Preuschoft, & N. Gomberg (Eds.), Environment, behavior, and morphology: Dynamic interactions (pp. 119–138). New York: Gustav Fischer. Niemitz, C. (1984). An investigation and review of the territorial behaviour and social organization of the genus Tarsius. In C. Niemitz (Ed.), Biology of tarsiers (pp. 117–128). New York: Gustav Fischer
  22. ^ Körner, C. (2007). The use of ‘altitude’ in ecological research. Trends in Ecology and Evolution, 22, 569–574.
  23. ^ Rae, T. C., Hill, R. I., Hamada, Y., & Koppe, T. (2003). Clinal variation of maxillary sinus volume in Japanese macaques (Macaca fuscata). American Journal of Primatology, 59, 153–158.
  24. ^ Izard, Kay M.; Wright, Simons (1985). "Gestation length in Tarsius bancanus". Am J Primatology 4 (4): 327–331. doi:10.1002/ajp.1350090408. 
  25. ^ Roberts, M.; Kohn, F. (1993). "Habitat Use, Foraging Behavior, and Activity Patterns in Reproducing Western Tarsiers, Tarsius bancanus, in Captivity: A Management Synthesis" (PDF). Zoo Biology 12 (2): 217–232. doi:10.1002/zoo.1430120207. 
  26. ^ Shekelle, M.; Nietsch, A. (2008). "Tarsier Longevity: Data from a Recapture in the Wild and from Captive Animals" (PDF). In Shekelle, M.; Maryano, T.; Groves, C.; Schulze, H.; Fitch-Snyder, H. Primates of the Oriental Night. LIPI Press. pp. 85–89. ISBN 978-979-799-263-7. 
  27. ^ Severn, K.; Dahang, D.; Shekelle, M. (2008). "Eastern Tarsiers in Captivity, Part I: Enclosure and Enrichment" (PDF). In Shekelle, M.; Maryano, T.; Groves, C.; Schulze, H.; Fitch-Snyder, H. Primates of the Oriental Night. LIPI Press. pp. 91–96. ISBN 978-979-799-263-7. 
  28. ^ Severn, K.; Dahang, D.; Shekelle, M. (2008). "Eastern Tarsiers in Captivity, Part II: A Preliminary Assessment of Diet" (PDF). In Shekelle, M.; Maryano, T.; Groves, C.; Schulze, H.; Fitch-Snyder, H. Primates of the Oriental Night. LIPI Press. pp. 97–103. ISBN 978-979-799-263-7. 
  29. ^ Fitch-Snyder, H. (2003). "History of Captive Conservation of Tarsiers". In Wright, P.C.; Simons, E.L.; Gursky, S. Tarsiers: Past, Present, and Future. Rutgers University Press. pp. 227–295. ISBN 0-8135-3236-1. 
  30. ^ Jachowski, David S.; Pizzaras, Carlito (2005). "Introducing an innovative semi-captive environment for the Philippine tarsier (Tarsius syrichta)". Zoo Biology 24 (1): 101–109. doi:10.1002/zoo.20023. 
  31. ^ Shekelle, Myron; Salim, Agus. "Siau Island Tarsier". IUCN/SSC Primate Specialist Group. Retrieved January 2010. 
  32. ^ "Totally Protected Animals of Sarawak". Forestry Department of Sarawak. Retrieved January 2010. 
General references

External links[edit]