Diversity
The genus
Tarsius
is the only genus in the family
Tarsiidae
. This small nocturnal primate genus consists of 10 tarsier species including;
T. dentatus
,
T. fuscus
,
T. lariang
,
T. pelengensis
,
T. pumilus
,
T. sangirensis
,
T. supriatnai
,
T. tarsier
,
T. tumpara
, and
T. wallacei
(Groves, 2018). Tarsiers are recognized by their large, beady, reddish-orange eyes
and tiny stature. They weigh between 80 and 150 grams (Welman, 2017) and have an average
body length of 12 centimeters (Merker, 2008). All species experience sexual dimorphism
and females tend to be smaller than males. The fossil record of tarsiers dates to
between 34 and 56 million years ago, in the Eocene era (Zijlstra, 2013).
Geographic Range
Tarsiers inhabit tropical forests and islands of Southeast Asia. The island archipelagos
of Southeast Asia include Sumatra, Borneo, Sulawesi, the southern Philippines, and
smaller neighboring islands. There are 3 clades of living
Tarsius
species; western tarsiers, Philippine tarsiers, and Sulawesi tarsiers (Driller, 2015).
These clades are composed evolutionarily and geographically, as some species are only
found on certain islands or in particular regions. Fossils of Eocene and Miocene tarsiers
are found in China, Thailand, and southern Pakistan (Zijlstra, 2013).
- Other Geographic Terms
- island endemic
Habitat
Tarsiers strictly inhabit forests of Southeast Asia. They reside in both primary and
secondary habitats. These arboreal primates are found in forests that range in density
and agriculture from island to island. Tarsiers main mode of locomotion is leaping
from tree to tree. Tarsiers, being noctural, sleep during the daylight and predominantly
roost in dense vegetation (Merker, 2008). Vegetation includes shrubs, bamboo, palm,
dense thickets of grass, bush, thorn scrubs, and secondary habitats on plantations
for logging and growing coffee, nutmeg, coconut, or coca crops (Gron, 2010) (MacKinnon,
1980).
- Habitat Regions
- tropical
- terrestrial
- Terrestrial Biomes
- forest
- rainforest
- Other Habitat Features
- agricultural
Systematic and Taxonomic History
Of living primates,
Anthropoidea
are most closely related to
Tarsius
(Ross, 2000).
There is strong debate regarding
Tarsius
phylogeny. Tarsiers were once accepted to be of the
Strepsirrhini
suborder, grouped with
Lemuroidea
and
Lorisidae
(WiesemĂŒller, 1999) because of their similar appearance, small stature, and nocturnal
nature. It is now widely accepted that tarsiers are members of the suborder haplorrhine,
grouped with anthropoids (Ross, 2000). Based on phylogenetic research, including molecular
data, tarsiers are more closely related to humans and apes then lemurs and lorises.
Some scholarly articles suggest dividing the genus into 3 and some references reflect
this attempted revised taxonomy. This taxonomic discrepancy is strongly supported
by data collection of physiological attributes such as coat colors, tail lengths,
and size, as well as molecular data (Groves and Shekelle, 2010).
Physical Description
Tarsiers are small furry primates with large red eyes, small dentition, and short
limbs and hands relative to other primates (Groves, 2010). Tarsier eye size, relative
to body size, is the largest of any mammal and directly correlates to their nocturnal
behavior (Gillian, et al. 2016). Tarsier dentition indicates an insectivorous diet,
but some species will prey on small birds and rodents, crabs, frogs, bats, or snakes
(MacKinnon, 1980). Their pelage is mostly grey, with hues of red, yellow, or brown
(Gron, 2010).
Tarsius
species that inhabit different geographic ranges may exhibit differences in coat
color, eye size, dentition, limb proportions, and hair length of tails or heels (Gron,
2010). Tarsiers are sexually dimorphic, where females are smaller in size than males
(Welman et al, 2017). Tarsiers vary in size, ranging from 80-150 grams (Welman et
al, 2017) and 10-15 centimeters long (Merker and Yustian, 2008). Tarsiers possess
a unique spinal column that permits the ability to turn their heads almost 360 degrees.
Other unique adaptations include the claws on their second and third digits, padded
fingers, and long tarsal bones at their heels (Gron, 2010).
- Other Physical Features
- endothermic
- bilateral symmetry
- Sexual Dimorphism
- male larger
Reproduction
Some species of
Tarsius
remain in lifelong groups of both males and females, while in other species the males
and females rarely interact and even occupy different geographical ranges (Van Shaik
and Kappeler, 1997). Some tarsier species enact mating rituals of "duetting", or mating
calls that entail one party chattering out and another responding with a similar chatter.
Some species that live in groups demonstrate alloparental care, where members occasionally
look after another memberâs young. Other species practice monogamous pair mating,
where only parents will interact with their offspring. Mating pairs are territorial,
while individuals in social species are often not (MacKinnon, 1980). Tarsier juveniles
often have an orange tinge to their coat hair (Shekelle and Nietch, 2008). Juveniles
grow to half the size of an adult tarsier in about 3 months, but are still smaller
than adults until about 2 years of age (MacKinnon, 1980).
- Mating System
- monogamous
- polygynandrous (promiscuous)
- cooperative breeder
Tarsiers have 2 mating seasons, in 6 month intervals. They exhibit mating calls referred
to as "duets" to find and monitor mate ranges. All species designate a spot to roost
in dense vegetation, usually either in pairs or groups. Occasionally young males seeking
a group or mate will be alone for a period of time. Some species that stay in groups
will let males join. Other species form groups that are exclusively male or female,
and the two sexes only come into contact to breed. Females give birth to one offspring
at a time (MacKinnon, 1980).
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
For the first three weeks of an infant tarsier's life, it is common for the mother
to carry them in their mouths whenever they move. In pair-bonded species fathers also
carry infants in their mouths. While mothers hunt, the infants are often left on a
tree branch for intervals of time. In a monogamous pair both parents will visit the
infant during this time. In groups other group members might make brief visits to
check up on the infant while the mother is away. Once the infant is about a month
old it begins hunting on its own, but remains in the group and within visible range.
Females often remain in their parental group throughout their life, unless forming
monogamous pairs. Males often leave to live alone or join other groups between 1 to
2 years of age (MacKinnon, 1980).
- Parental Investment
- altricial
- male parental care
- female parental care
- post-independence association with parents
- extended period of juvenile learning
- inherits maternal/paternal territory
Lifespan/Longevity
Longevity and lifespan has not yet been established for many species of
Tarsius
. Any evidence of captive lifespan is not directly applicable to wild tarsier lifespan.
The longest reported lifespan in captivity is over 17 years. The oldest individual
caught in the wild is estimated at 10 years old. Tarsier behavior changes due to old
age between 14 and 16 years of age. Signs of advanced aging may include graying of
hair around the face and dental wear (Shekelle and Nietch, 2008).
Behavior
Tarsiers are nocturnal mammals that awake around sunset and spend the nights foraging
for insects, eating, traveling between trees, resting, and socializing. Socialization
includes grooming each other, scent marking, vocalizing (including duetting), and
playing (Gursky, 1998). Males travel longer distances and occupy a larger area, while
females hunt more efficiently and consume more insects (Neri-Arboleda et al, 2002).
Tarsiers are both monogamous and polygynous. Some live in pairs, groups of variable
size, and some males may live alone. (Gursky-Doyen, 2010).
- Key Behaviors
- arboreal
- nocturnal
- crepuscular
- motile
- sedentary
- solitary
- territorial
- social
Communication and Perception
Tarsiers communicate through vocalization and scent marking. Vocalizations include
high pitched whistles and chattering melodies referred to as duets. High-pitched whistles
are varied from simple calls to predator warnings. Some tarsiers have distinct vocalizations
to mob, or ward off, a predator (Gursky-Doyen 2010). The duet vocalizations are likely
a mating call to lead males to females. Scent marking on trees is used to attract
mates and warn off competitors by marking territory (Neri-Arboleda, 2002).
- Other Communication Modes
- duets
- scent marks
Food Habits
Tarsiers consume an exclusively carnivorous diet. Their diet is mostly insectivorous,
but some species will prey on small birds and rodents, crabs, frogs, bats, or snakes
(MacKinnon, 1980). Vision adaptations allow for hunting at night, through dense areas
of forests (Welman et al, 2017). Limb adaptions allow for quick leaping locomotion
between trees while capturing prey. They hunt prey on the ground, in the air, and
on tree branches and leaves (Gron, 2010). Tarsiers capture methods typically include
grabbing with strong, long fingers or leaping onto prey (Gron, 2010).
- Primary Diet
-
carnivore
- eats terrestrial vertebrates
- insectivore
Predation
The primary predators of tarsiers are monitor lizards, civets, snakes, and diverse
birds of prey. In the presence of bird predators, individuals vocalize and disperse
to hide. When in the presence of a terrestrial predator, such as a snake, individuals
âmobâ the threat. When mobbing, all individuals respond to a threat with vocalizations
as each repeats lunging towards and retreating from the predator (Gursky, 2002). Recent
studies suggest predation by domestic animals as habitats grow smaller, and people
who capture and sell (Shekelle and Nietch, 2008) or who erroneously consider them
pests in farmland (Canete, 2003).
- Anti-predator Adaptations
- cryptic
Ecosystem Roles
Tarsier niches are largely as predator and prey. Their presence affects the population
size of organisms that they feed on and of those who feed on them. They are host to
many different endo- and ectoparasites, including mites and intestinal worms (Shekelle
and Nietch, 2008).
- mites ( Acari )
- intestinal worms
Economic Importance for Humans: Positive
Tarsiers draw crowds of eco-tourism, trophy hunters, and animal collectors. Some natives
to Southeastern Asia, where tarsiers reside, make a living off of the attraction they
draw (Canete, 2003).
- Positive Impacts
- pet trade
- food
- ecotourism
Economic Importance for Humans: Negative
Like most primates, some parasites and diseases can be passed from tarsiers to humans.
Although some agriculturalists consider them pests, this is a misconception because
they do not negatively impact crops or farmland (Canete, 2003).
- Negative Impacts
-
injures humans
- causes disease in humans
- carries human disease
Conservation Status
Habitat loss and deforestation contributes to a decline in tarsier populations (Merker
and Yustian, 2008). Currently, tarsiers reside in many protected areas.
T. bancanus
,
T. dentatus
, and
T. tarsier
are considered vulnerable.
Tarsius syrichta
is considered near threatened.
Tarsius pelengensis
and
T. sangirensis
are considered endangered.
Tarsius tumpara
is considered critically endangered.
Tarsius lariang
,
T. pumilus
, and
T. wallacei
are listed as data deficient. Tarsiers are protected through international treaties
(Shekelle et al, 2018).
Other Comments
Four fossil species are known. Specimen are dated from the middle Eocene of China,
middle Miocene of Thailand, Oligocene of Egypt, Miocene of Lybia, and Eocene of Myanmar
(Zijlstra, 2013). Because of the interest toward dividing the genus into 3, some species
are referred to as the attempted revised taxonomic names including the genera
Carlito
and
Cephalopachus
. Molecular data and physiological differences noted by Groves and Shekelle suggest
this may be true. There may be some cryptic species of
Tarsius
yet to be discovered (Groves and Shekelle, 2010).
Additional Links
Contributors
Sabrina Archuleta (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
- oriental
-
found in the oriental region of the world. In other words, India and southeast Asia.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- island endemic
-
animals that live only on an island or set of islands.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- rainforest
-
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
- agricultural
-
living in landscapes dominated by human agriculture.
- monogamous
-
Having one mate at a time.
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- cooperative breeder
-
helpers provide assistance in raising young that are not their own
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- altricial
-
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
- male parental care
-
parental care is carried out by males
- female parental care
-
parental care is carried out by females
- arboreal
-
Referring to an animal that lives in trees; tree-climbing.
- nocturnal
-
active during the night
- crepuscular
-
active at dawn and dusk
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- solitary
-
lives alone
- territorial
-
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
- social
-
associates with others of its species; forms social groups.
- visual
-
uses sight to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- duets
-
to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate
- scent marks
-
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- cryptic
-
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
- pet trade
-
the business of buying and selling animals for people to keep in their homes as pets.
- food
-
A substance that provides both nutrients and energy to a living thing.
- ecotourism
-
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
- causes disease in humans
-
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
- carnivore
-
an animal that mainly eats meat
- insectivore
-
An animal that eats mainly insects or spiders.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
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