The pig-tailed langur (''Simias concolor''),
monotypic
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
in
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''Simias'', is a large
Old World monkey
Old World monkey is the common English name for a family of primates known taxonomically as the Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons ...
, endemic to several small islands off the coast of
Sumatra
Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...
in
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
. Its face is black, its fur is black-brown and it has a relatively short tail. It is a diurnal species, feeding in the rainforest canopy on leaves, and to a lesser extent, fruit and berries. Little is known of its natural history, but it is heavily hunted, its populations have been declining rapidly and the
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
has assessed its conservation status as being "
critically endangered".
It has been included on a list of
the World's 25 Most Endangered Primates
The World's 25 Most Endangered Primates is a list of highly endangered primate species selected and published by the International Union for Conservation of Nature (IUCN) Species Survival Commission (SSC) Primate Specialist Group (PSG), the In ...
.
As an
arboreal
Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...
primate the pig-tailed langur spends most of its time in the canopy devoting the majority of its activity budget towards resting and feeding.
The structure of groups is single-male, multi-female. Group sizes range from around 3 to 9 individuals depending on locations and hunting pressures.
There are two
subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
of this primate, ''Simias concolor concolor'' which lives in the southern
Mentawai islands Mentawai may refer to:
* Mentawai Islands
* Mentawai Strait
* Mentawai people
* Mentawai language
The Mentawai language is an Austronesian language, spoken by the Mentawai people of the Mentawai Islands, West Sumatra, Indonesia.
Dialects
Acco ...
, and ''Simias concolor siberu'' which lives exclusively in the northern island of
Siberut
Siberut is the largest and northernmost of the Mentawai Islands, located 150 kilometres west of Sumatra in the Indian Ocean. It covers an area of 3,838.25 km2 including smaller offshore islands, and had a population of 35,091 at the 2010 Cens ...
.
Sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
and
sexual swelling
Sexual swellings are enlarged areas of genital and perineal skin occurring in some female primates that vary in size over the course of the menstrual cycle. Thought to be an honest signal of fertility, male primates are attracted to these swell ...
is exhibited by this species.
Population estimates from the 1980s compared to data from the 2000s show a decrease in population size.
The northern island of Siberut shows a greater abundance of this species in comparison to the southern Mentawai islands. This can largely be attributed to the difference in conservation efforts as much of northern Siberut has been declared a
national park
A national park is a nature park, natural park in use for conservation (ethic), conservation purposes, created and protected by national governments. Often it is a reserve of natural, semi-natural, or developed land that a sovereign state dec ...
whereas the southern islands have been historically devastated by
commercial logging
Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars.
Logging is the beginning of a supply chain ...
.
This species is subject to hunting by local inhabitants. The reduction in forestry cover has allowed for greater levels of human activity and settlement which facilitates hunting, especially in the southern islands since most areas are unprotected.
Description
The pig-tailed langur is a large and rather heavily built
Old World monkey
Old World monkey is the common English name for a family of primates known taxonomically as the Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons ...
, adapted to climbing with its long arms. Its fur is black-brown, and its hairless face is also black. It is the only monkey in the subfamily
Colobinae
The Colobinae or leaf-eating monkeys are a subfamily of the Old World monkey family that includes 61 species in 11 genera, including the black-and-white colobus, the large-nosed proboscis monkey, and the gray langurs. Some classifications spli ...
to have a relatively short tail; the tail is only slightly furred and is only long. The short nose is pointed upward. The pig-tailed langur reaches a full grown length of approximately and a weight of .
Sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
is exhibited by this species with adult males being larger and heavier than adult females.
Sexual swelling
Sexual swellings are enlarged areas of genital and perineal skin occurring in some female primates that vary in size over the course of the menstrual cycle. Thought to be an honest signal of fertility, male primates are attracted to these swell ...
is exhibited by this species which is rare for single male multi female groups of
Colobinae
The Colobinae or leaf-eating monkeys are a subfamily of the Old World monkey family that includes 61 species in 11 genera, including the black-and-white colobus, the large-nosed proboscis monkey, and the gray langurs. Some classifications spli ...
monkeys.
Classification
Many researchers would like to reclassify this species into the ''
Nasalis'' genus but phylogenic analyses suggest that these two groups should remain in their separate sister taxa.
The
Critically Endangered status of this primate gives even more reason for it to remain under the genus ''Simias'' since the grouping of these genera could affect conservation efforts.
Diet
It is an
omnivore
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...
with a diet consisting of
leaves
A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
,
flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
s,
fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
s and occasionally
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
s. The availability of these foods in this area are abundant especially in unripe and ripe fruits.
Leaves are the most abundant in their diet followed by fruits.
As with all other
Colobinae
The Colobinae or leaf-eating monkeys are a subfamily of the Old World monkey family that includes 61 species in 11 genera, including the black-and-white colobus, the large-nosed proboscis monkey, and the gray langurs. Some classifications spli ...
primates, this species is
diurnal.
Distribution and social systems
This
primate
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...
is
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to the
Mentawai Islands Mentawai may refer to:
* Mentawai Islands
* Mentawai Strait
* Mentawai people
* Mentawai language
The Mentawai language is an Austronesian language, spoken by the Mentawai people of the Mentawai Islands, West Sumatra, Indonesia.
Dialects
Acco ...
, there are two subspecies, ''Simias concolor concolor'' also known as simasepsep which resides on the southern islands of
Sipora
Sipora (Indonesian: ''Sipora'' or sometimes spelled ''Sipura'') located off Sumatra in the West Sumatra Province of Indonesia, is the second-smallest and most developed of the four Mentawai Islands at only 651.55 km2. It had a population o ...
,
North Pagai
North Pagai (Indonesian: ''Pagai Utara'') is the smallest of the four principal Mentawai Islands off the west coast of Sumatra in Indonesia. It is south of Sipora and north of South Pagai (or Pagai Selatan) Island.
The population figure given f ...
, and
South Pagai
South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both east and west.
Etymology
The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþaz' ...
.
[Yanuar, A., & Supriatna, J. (2018). The Status of Primates in the Southern Mentawai Islands, Indonesia. ''Primate Conservation'', ''32'', 193–203] The second subspecies is ''Simias concolor siberut'' also known as simakobou which lives only on the island of
Siberut
Siberut is the largest and northernmost of the Mentawai Islands, located 150 kilometres west of Sumatra in the Indian Ocean. It covers an area of 3,838.25 km2 including smaller offshore islands, and had a population of 35,091 at the 2010 Cens ...
.
It is a
diurnal and
arboreal
Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...
rain forest dweller, often spending spending most of its time in the canopy but occasionally comes to ground.
The activity budget of this primate is mostly resting and feeding with a small fraction of time devoted towards travel and social behavior.
Some studies in the
Siberut
Siberut is the largest and northernmost of the Mentawai Islands, located 150 kilometres west of Sumatra in the Indian Ocean. It covers an area of 3,838.25 km2 including smaller offshore islands, and had a population of 35,091 at the 2010 Cens ...
area show relatively low group sizes (mean group size 2.6).
Other parts in
Siberut
Siberut is the largest and northernmost of the Mentawai Islands, located 150 kilometres west of Sumatra in the Indian Ocean. It covers an area of 3,838.25 km2 including smaller offshore islands, and had a population of 35,091 at the 2010 Cens ...
show relatively high group sizes (mean group size 8.7).
The reason for different group sizes is not factually known, however many researchers suggest that it could be due to anthropogenic factors such as hunting and deforestation.
The pig-tailed langur has single-male, multi-female groups. The mating system of this species follows a
polygynous
Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women.
Incidence
Polygyny is more widespread in Africa than in any ...
structure although it was originally thought to be
monogamous
Monogamy ( ) is a form of Dyad (sociology), dyadic Intimate relationship, relationship in which an individual has only one Significant other, partner during their lifetime. Alternately, only one partner at any one time (Monogamy#Serial monogamy, ...
.
Endangerment status and threats to conservation
This species is classified as
Critically endangered by the
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
.
[Quinten, M, Setiawan, A., Cheyne, S., Traeholt, C. & Whittaker, D. 2020. ''Simias concolor''. The IUCN Red List of Threatened Species 2020: e.T20229A17953422.] It was classified as
Endangered (IUCN status) up until 2008 were the endangerment status was changed to
Critically Endangered.
It is among
The World's 25 Most Endangered Primates
The World's 25 Most Endangered Primates is a list of highly endangered primate species selected and published by the International Union for Conservation of Nature (IUCN) Species Survival Commission (SSC) Primate Specialist Group (PSG), the In ...
due to the many
anthropogenic
Anthropogenic ("human" + "generating") is an adjective that may refer to:
* Anthropogeny, the study of the origins of humanity
Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows:
* Human im ...
pressures it faces on the islands
[Schwitzer, C., Mittermeier, R.A., Rylands, A.B., Chiozza, F., Williamson, E.A., Byler, D., Wich, S., Humle, T., Johnson, C., Mynott, H., and McCabe, G. (eds.). 2019. ''Primates in Peril: The World’s 25 Most Endangered Primates 2018–2020''. IUCN SSC Primate Specialist Group, International Primatological Society, Global Wildlife Conservation, and Bristol Zoological Society, Washington, DC. 57-58pp] which include, destruction of forest for commercial use, hunting and illegal pet trade.
[Yanuar, A., & Supriatna, J. (2018). The Status of Primates in the Southern Mentawai Islands, Indonesia. ''Primate Conservation'', ''32'', 193–203] Population size estimates have been conducted across many years with varying islands being chosen for research areas. In the 1980s population estimates of the Pig-tailed langur was 19,000 on the island of Siberut and 26,000 across all four islands.
In 2004 Lisa M. Paciulli dedicated their
PhD dissertation
A thesis ( : theses), or dissertation (abbreviated diss.), is a document submitted in support of candidature for an academic degree or professional qualification presenting the author's research and findings.International Standard ISO 7144: ...
towards studying threats to Mentawai island primates and determining
population densities
Population density (in agriculture: standing stock or plant density) is a measurement of population per unit land area. It is mostly applied to humans, but sometimes to other living organisms too. It is a key geographical term.Matt RosenberPopu ...
associated with logging pressures.
[Paciulli, L. M. 2004. The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates. PhD thesis, State University of New York, Stony Brook.] Population estimates were found to be around 6,700-17,300 across all islands with a large amount of variation being attributed due to hunting and logging pressures.
Population densities were 2.5 individuals/km
2 in logged areas whereas unlogged areas had a population density of 5 individuals/km
2.
An extensive population density survey was conducted by the
University of Indonesia
The University of Indonesia ( id, Universitas Indonesia, abbreviated as UI) is a public university in Depok, West Java and Salemba, Jakarta, Indonesia. It is one of the oldest tertiary-level educational institutions in Indonesia (known as the Dut ...
on four endemic Mentawai primates. This research was exclusive to the southern Mentawai islands and included a variety of survey areas, most of which devastated by
commercial logging
Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars.
Logging is the beginning of a supply chain ...
. The results of the 2008-2009 surveys are population densities of 1.5 groups/km
2 on the island of Sipora and 2.1 ± 0.3 groups/km
2 on the Pagai islands with group sizes around 3 individuals.
Research into population densities on the northern Mentawai island of Siberut is more abundant due to the lower mean population densities of humans living on this island as well as the considerable amount of forestry that remains in comparison to the southern Mentawai islands. In northern Siberut researchers in the Peleonan forest conducted population density surveys from July to December of 2005.
Results form these surveys show a mean density of 16.2 groups/km
2.
One of the main factors associated with the population decline of this species is habitat disturbance from commercial logging operations.
Forestry cover varies significantly among the islands. The island of Siberut has most of its area declared as a
National park
A national park is a nature park, natural park in use for conservation (ethic), conservation purposes, created and protected by national governments. Often it is a reserve of natural, semi-natural, or developed land that a sovereign state dec ...
whereas the southern islands of Sipora, North Pagai, and South Pagai have limited areas of forestry conservation.
It is estimated that Siberut's forest cover decreased from 3,500km
2 to 2,400km
2 and the southern Mentawai islands of Sipora and Pagai have decreased from 1300km
2 to 300km
2.
The reason for Siberut's extensive forestry cover in comparison to the southern islands is due to historical conservation efforts. Much of the efforts started in the 1980s with the help of
UNESCO man and the Biosphere reserve.
This was expanded in the 1990s were a large portion of Siberut was declared a National Park.
The declaration of this National Park allowed for hunting and logging operations to be significantly reduced; although areas around the national park still experience pressures of logging and conversions to commercial palm oil plantations through concessions and illegal activities.
Many of the areas in the southern Mentawai islands have experienced heavy logging operations that have left little forestry for the Mentawai primates. Most of the forestry has now been reduced from
primary forestry to
secondary forestry which is troubling since the pig-tailed langur thrives in arboreal environments.
The reduction on forestry in the southern Mentawai islands creates a domino effect of paving new land for more human activities and settlement.
The second main factor associated with the population decline of this species is
hunting
Hunting is the human activity, human practice of seeking, pursuing, capturing, or killing wildlife or feral animals. The most common reasons for humans to hunt are to harvest food (i.e. meat) and useful animal products (fur/hide (skin), hide, ...
. Local inhabitants have historically used arrows and poisonous materials to hunt this species.
However technological advancements of firearms have facilitated the hunting of this species, especially since it is one of the largest primates on these islands.
Many local inhabitants hunt this species because it is considered a delicacy, with many locals saying it has the best tasting meat compared to other primates.
Population density data suggests that an increase in hunting pressure at survey sites results in lower population densities of this primate.
Subspecies
* Genus ''Simias''
** Pig-tailed langur, ''Simias concolor''
*** ''Simias concolor concolor''
*** ''Simias concolor siberu''
References
{{Taxonbar, from=Q617979
Colobinae
Endemic fauna of Indonesia
Fauna of Sumatra
Mammals of Indonesia
langur
The Colobinae or leaf-eating monkeys are a subfamily of the Old World monkey family that includes 61 species in 11 genera, including the black-and-white colobus, the large-nosed proboscis monkey, and the gray langurs. Some classifications spli ...
Critically endangered biota of Asia
Mammals described in 1903
Species endangered by habitat loss
Species endangered by use as food
Species endangered by the pet trade
Taxa named by Gerrit Smith Miller Jr.