It’s NOT a Monkey: The Tarsier

One of the biggest pet peeves of a primatologist (a person who studies primates), let alone most biologists, is when people call primates ‘monkeys’. Primates are a highly diverse group that includes the Great ApesOld World MonkeysNew World MonkeysProsimians and Humans [1]. Sometimes misbehaving humans are also referred to as monkeys, but is that accurate? Nope.

Tarsiers are a good example of this mis-categorization as tarsiers are NOT monkeys. Monkeys and tarsiers are both Haplorhines, but tarsiers are not monkeys. It’s like comparing mugs and glasses. Mugs and glasses both hold liquids, but a mug is not a glass, and a glass is not a mug, but both mugs and glasses are cups.

There has been great debate regarding this classification of tarsiers. They were originally classified within the Suborder Strepsirhine which includes lemurs and galagos. Currently, however, they are classified as Haplorhines (also known as Anthropoids) which are a taxonomic grouping that includes monkeys, apes, humans and tarsiers. The difficulty with the classification of tarsiers arose because they share some traits with Strepsirhines, but share more traits with haplorhines [2,3].

See the figure below to see how:

tarsier-classification
http://image.wikifoundry.com/image/1/Vb7-Z_qYeGwNuPdH_pZkdA57433/GW525H584

Some of the traits tarsiers share with Haplorhines are a fused frontal bone, an absent reflective eye layer, and an absent rhinarium (think of a wet nose similar to a dog) [2,3]. However, tarsiers also share traits with Strepsirhines, otherwise  known as Prosimians. Prosimians are a primitive group of primates (prosimian literally translates to “pre-monkey”). Indeed, the word “primitive” refers to a “derived characteristic that more closely resembles a non-primate ancestral common ancestor” [2,4]. However, prosimians, unlike tarsiers,  have a dental comb, which is a set of teeth on their lower jaw used for grooming and scraping gum off trees. This absent dental comb is one of the primary features separating tarsiers from a classification as prosimians. Currently tarsiers are classified in their own infraorder, tarsiiformes [3].

Aside from all of that of taxonomic classification, tarsiers are adorably cute, proof below:

_dsc4144

A 6 year old male tarsier hiding under some leaves.

If you are headed to the Philippines and to the island of Bohol there are two things you cannot miss. The first are the Chocolate Hills, which is a small region in Bohol with conical hills as far as the eye can see. There is no scientific consensus as to why these hills exist, but perhaps you can ponder that question while you admire their beauty [5]. The second is the Philippine Tarsier Foundation’s Tarsier Sanctuary, located near Corella outside Tagbilaran City by 45 minutes.

_dsc4169

 The Chocolate Hills, Bohol, The Visayas, Philippines.

The Sanctuary is 167 hectares, located off the road in a secondary forest. It houses one of the world’s smallest and most endangered primates, The Philippine Western tarsier (T. Syrichta) [6]. This tiny primate ranges in size from 12 to 15 cm and weighs approximately 105 to 135 grams. These nocturnal beasties have the biggest eye to body ratio of any animal on the planet, giving tarsiers acute night vision. However, their eyes are fixed in place and cannot move to look in different directions like our human eyes can. To compensate, tarsier’s spines allow their heads to turn 180 degrees each way. They are also highly capable of sound detection because of their large ears, essentially making them like little primate owls. Furthermore, their tarsal bone in their leg is elongated, allowing them to leap long distances. Their long tarsal bone is also where they get their name. They are ferocious, albeit tiny, insectivores that also eat birds, fruit, and scorpions [6,7].

Perhaps the saddest thing about tarsiers is that they frequently die in captivity as they attempt to escape a stressful environment or situation. While this may seem like suicide to the casual observer it’s actually the fatal result of a failed escape attempt. Tarsiers are sensitive to daylight, noise and physical contact. When interviewed, Carlito Pizarras, the field manager at the Philippine Tarsier and Wildlife Sanctuary said, “People go near and they’re loud, or make a picture with the flash, or they’re touching them. If you put them in a cage they want to go out. That’s why they bump their heads on the cage  {as they try to escape}, and it will crack because the cranium is so thin” [8].

Even though tarsiers in the Philippine Tarsier and Wildlife Sanctuary are in an open environment, bear in mind that they are still wild animals. If you go to the sanctuary to meet them be sure to follow the tips from “How to meet a monkey” to ensure that you don’t cause them any unnecessary stress. In particular, don’t forget to turn off your camera’s flash, as this sudden bright light is one of the most common causes of stress from tourists.

Tarsiers are listed as “Near Threatened” by the International Union for the Conservation of Nature. The main reason for the decline in populations is a high infant mortality rate [9]. Female tarsiers spend 6 months in gestation (the period of time for the fetus to grow until birth) and require 24 grams of food a day. This is double the food intake of a tarsier that isn’t pregnant! They then spend 6 months weaning the infant off the mother so that it can live independent of her [7]. When I visited in October we were told that the females were absent because it was mating season (October – March).

Another factor contributing to their conservation status is habitat degradation from slash and burn practices which damage their natural habitat of primary rainforest [9]. Male tarsiers are quite territorial, and each male requires a full hectare of space [7]. With only 167 hectares, the sanctuary is barely large enough for the small population of tarsiers in its boundaries.

The last and most abhorrent factor contributing to their conservation status is that tarsiers are often sold in illegal markets for meat or as pets [9]. Though it is not illegal, there is one other facility known as the Loboc Tarsier Conservation Area in Bohol that has tarsiers. However, these tarsiers are caged, creating a stressful environment that can contribute to tarsiers’ fatal escape attempts [10]. I urge you to avoid this facility because of their poor management and the conditions in which they keep their tarsiers. To avoid confusion between the two facilities, the better managed Sanctuary is located in Corella, not Loboc.

The Philippine Tarsier is now protected by Filipino law. There are harsh penalties for hunting tarsiers and the illegal animal trade. Thankfully, through the fantastic work of the Sanctuary more awareness is being brought to the public about their habitat degradation and the illegal animal trade. These steps are monumental in the conservation of the Philippine tarsier. With all of these efforts combined, let’s hope to see more tarsiers in the wild.

Personally, this biologist feels that the first step to ensure that tarsiers don’t go extinct is to recognize that it is a NOT A MONKEY, but a unique primate worthy of their own distinction.

To get more information on the tarsiers or to plan your trip to the Sanctuary, click here.

 

Works Cited:

[1] Primate Factsheets Glossary. (2011). Wisconsin Primate Research Center Library. Retrieved on November 28, 2016 from http://pin.primate.wisc.edu/factsheets/glossary#187.

[2] Smith, C. (2011). Classifying Tarsiers: Confounding Traits and the Difficulty in Taxonomic Placement. Retrieved from https://biology.knoji.com/classifying-tarsiers-confounding-traits-and-the-difficulty-in-taxonomic-placement/.

[3] Moore, S. (2015) Primate Classes [Class Handout] Department of Anthropology, Houston Community College, Texas, USA.

[4] Blashfield, J. F. (2016). Prosimians. Retrieved from http://science.jrank.org/pages/5517/Prosimians.html

[5] Jsselstein, I. (2002). The Chocolate Hills. Retrieved from http://bohol.ph/article6.html

[6] The Tarsier Foundation Incorporated. (2016). The Tarsier Sanctuary. Retreived from http://tarsierfoundation.org/news/the-tarsier-sanctuary.

[7] Gron, K. J. (2010). Primate Factsheets: Tasier (Tarsius) Taxonomy, Morphology, & Ecology. Retrieved from http://pin.primate.wis.edu/factsheets/entry/tarsier.

[8] Zelman, J. (2011). Tarsiers threatened by tourism and hunting. The Huffington Post US Edition. Retrieved from http://www.huffingtonpost.com/2011/12/12/tarsiers-threat-humans_n_1143915.html#s537565

[9] Shekelle, M., & Arboleda, I. (2008). Tarsius syrichta. The IUCN Red List of Threatened Species 2008: e.T21492A9289252. doi: http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T21492A9289252.en.

[10] Adalid, A. (2016, February 9). [Web Log Message]. Why you should avoid Loboc Conservation Area in Bohol. Retrieved from http://iamaileen.com/bohol-philippines-loboc-tarsier-conservation-area/

***If any information is ever incorrect, please let me know. I would be happy to update it with the most current information. Science is about learning from mistakes and moving forward!***

 

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