SOCIAL ORGANIZATION AND BEHAVIOR
Tarsiers exhibit variation in social system between species. The best
descriptor of T. tarsier social system may be monogamous with facultative
polygyny, where one male's range overlaps with that of another female, and
sometimes with multiple females whose ranges overlap (Gursky 1995; 2007a).
Genetic evidence suggests that T. lariang may also have a monogamous mating
system (Driller et al. 2009). Tarsiers outside of Sulawesi do not appear to
have a monogamous social organization. A dispersed (noyau) mating system, where
a male's range overlaps multiple female ranges, characterizes sociality among T.
bancanus and T. syrichta (Crompton & Andau 1987; Dagosto et al. 2001;
Neri-Arboleda et al. 2002).
In general, the western tarsiers (T. bancanus) are the least gregarious,
followed by the intermediate Philippine tarsier (T. syrichta), and finally with
the eastern species (all other species) showing the highest levels of sociality
(Shekelle 2003). Sociality within a tarsier species varies with resource
availability and predation. Spectral tarsiers decrease distances between group
members during times of higher food resource availability and increased
predation pressure (Gursky 2002b). T. dentatus also increases distances between
individuals in more disturbed habitats with fewer resources (Merker et al.
2005). T. spectrum is considerably gregarious both in and out of the sleeping
site, although outside the sleeping site group members usually are not in actual
physical contact with one another (Gursky 2000c). At sleeping sites, typical T.
tarsier social behaviors include playing, allogrooming, snuggling, vocalizing,
and scent-marking, while social behaviors with group members away from the
sleeping site include playing, allogrooming, snuggling, vocalizing,
scent-marking, food-sharing, and copulating (Gursky 2000c).
Photo: David Haring
Group size and composition varies both within and between tarsier species.
In spectral tarsiers (T. tarsier), there is significant variation in
group size (the number of individuals who share a sleeping site)
and composition (Gursky 1995). The average group size of T.
tarsier is 3.1 individuals and is comprised of at least a mated pair of
adults but also sometimes with an additional adult female, and often offspring
(MacKinnon & MacKinnon 1980; Gursky 1995; 2000b). Spectral tarsier groups
do not contain more than one adult male (Gursky 2006). Similarly, Dian's tarsier
groups usually consist of one adult male, one or more adult females, and their
offspring sharing a sleeping tree (Merker 2006). This species decreases group
size in disturbed habitats with fewer resources (Merker et al. 2005). In
contrast, T. bancanus do not sleep with other tarsiers and are usually found
solitary (Crompton & Andau 1987). T. syrichta are almost always alone as well
(Neri-Arboleda et al. 2002).
Tarsiers engage in territorial behaviors including defense through patrolling
and social encounters, as well as territorial advertisement through
scent-marking and vocalizations. Territorial defense is seen in the spectral
tarsier (T. tarsier) and likely functions most importantly in mate defense but
also may have other functions as well (Gursky 2003b; 2007a). Territorial
disputes in this species usually occur near the edges of a group's territory,
and consist of group members aggregating, calling toward, chasing and lunging at
the intruder (MacKinnon & MacKinnon 1980; Gursky 2003b; 2007a). T. bancanus
males also patrol their territories (Crompton and Andau 1986). In Sulawesi,
vocalizations may function as territorial advertisement, where both males and
females of T. tarsier, T. dentatus, and T. lariang perform morning duet
vocalizations (Gursky 2007a; Merker et al. 2005; Merker & Groves 2006).
Both T. tarsier and T. syrichta mark territory by depositing scent-marks within
and along home range boundaries (Gursky 1997; Neri-Arboleda et al. 2002). T.
dentatus establishes sleeping sites near the periphery of home ranges, which may
aid in the renewal of scentmarks along territorial boundaries (Merker 2006).
Both sexes of spectral tarsier (T. tarsier) disperse from their
natal sleeping sites. Males disperse on average 733 meters (2404.9 ft), much
farther than the female average of 360 meters (1181.1 ft) (Gursky 2007a).
The female sexual cycles of T. bancanus in captivity last on average
24 days (Wright et al. 1986b). The sexual cycles of T. syrichta
average 24.6 days (Catchpole & Fulton 1943). During estrus, the genitals of
female T. bancanus swell and become reddish, a state that
usually lasts for 6-9 days per cycle (Wright et al. 1986a; 1986b). In
captivity, female T. bancanus solicit courtship by performing genital
displays. Males then vocalize a "chirruping" call and sniff the genitals of the
female. Both sexes may urinate. Courtship may last from 60 to 90 minutes but
copulation itself lasts only around a minute and a half (Wright et al. 1986a).
Copulation occurs on a vertical perch, with the male mounting the female in a
dorsal-ventral position from behind and below. Post-copulation, the male will
groom his genitals and the female will rub herself on various objects nearby
(Wright et al. 1986a).
Wild spectral tarsiers (T. tarsier), unlike other tarsiers,
reproduce seasonally, with two observed mating seasons between April-June, and
again between October-November and corresponding birth peaks between April-May
and November-December (MacKinnon & MacKinnon 1980; Gursky 2007a). The
average inter-birth interval in wild T. tarsier is 13.5 months (Gursky
Estimated average gestation length in wild T. tarsier is 193 days
(6.3 months) (Gursky 2007a). Gestation in captive T. bancanus is
around 178 days (5.9 months), while recorded values for T. tarsier and T.
syrichta are 157 days (5.2 months) and 180 days respectively (5.9 months)
(Izard et al. 1985; Roberts 1994).
Photo: David Haring
T. bancanus females are capable of conceiving offspring at around
two years of age and T. tarsier are sexually mature at around 518 days
(17.0 months) (Roberts 1994).
Relative to their parents, infant tarsiers are very large at birth (20-33% of
adult weight) and are born with open eyes and fur (Roberts 1994; Gursky 2000a).
Tarsier infants are born as singletons (Roberts & Kohn 1993; Gursky 2007a).
In captivity, T. bancanus birth weights average 23.0 g (0.8 oz) and
T. syrichta birth weights average 23.2 g (0.8 oz) (Haring & Wright
1989; Roberts & Kohn 1993).
Wild infant spectral tarsiers T. tarsier are carried in the mouth of
the mother in the manner of a cat and almost never by clinging to the fur, a
pattern which is also seen in T. syrichta (Haring & Wright 1989;
Gursky 1994; 2007a). In some captive observations of T. bancanus,
mothers carried their offspring orally, in other studies this was not the case
with mothers never carrying their offspring orally (Niemitz 1984b; Roberts
1994). In the wild infant T. tarsier are carried about 20% the time
overall, but carriage declines as the infant ages (Gursky 2007a).
The captive T. bancanus infant first moves away from its mother at
10-15 days old. Skilled locomotion commences in captive T. bancanus
around 22-28 days old and mothers stop trying to carry their infant between 41
and 43 days old (Roberts 1994). T. tarsier and T. bancanus
infants are able to move quadrupedally before they are able to leap (Gursky
1997). In wild T. tarsier, the first leaps are seen at 32 days old
(Gursky 1997). Attempts to catch live prey in captive T. bancanus
start at an average of 37 days old (Roberts 1994). However, in the wild, a
T. tarsier infant was seen hunting at 26 days old (MacKinnon &
MacKinnon 1980). Wild T. tarsier hunting success is first met at 45
days old (Gursky 1997). Captive play in T. bancanus begins at an
average of 22.5 days old. Between 38 and 49 days old, the mother and infant
start to sleep apart, and completely cease to do so by 75 days old. Wild T.
tarsier nursing conflict peaks in the 8-9th weeks of life and infants are
weaned at an average of 80 days of age (Gursky 2007a). Weaning occurs at 80 days
in T. bancanus and 82 days old in T syrichta (Roberts 1994).
Perhaps the most interesting aspect of spectral tarsier (T. tarsier)
infant rearing is the large amount of time the infant spends alone (Gursky
1994). While she forages, a wild mother will "park" her offspring and leave it
by itself, occasionally visiting the infant (MacKinnon & MacKinnon 1980;
Roberts 1985). However, the T. tarsier mother usually stays relatively
close to the "parked" infant and will "park" it at an average of 11 different
times over the course of the night (Gursky 2002a). Until 70 days of age, T.
tarsier infants are "parked" more than half of the time, usually almost 6 m
(19.7 ft) above the ground and not in particularly concealed locations (Gursky
Allocare is seen in wild spectral tarsiers (T. tarsier), and may be
provided to the infant by subadults of both sexes and adult males with the most
non-maternal allocare provided by subadult females (Gursky 2000a). Types of
allocare that are seen include infant transport, food sharing, play, grooming,
baby-sitting, physical contact, and increased vigilance and alarm calling
(Gursky 2000a). While other group members sometimes carry the infant, the vast
majority of transport is provided by the mother (Gursky 2000a).
Infanticide has occurred in captive T. bancanus (Roberts 1994).
In general, tarsier communication has been described as elaborate (MacKinnon
& MacKinnon 1980; Shekelle 2003). There are noticeable differences in
vocalizations between, and in some cases within tarsier species, and playback
experiments with wild tarsiers have shown that such differences are recognized
by the tarsiers themselves. The implications of this are that groups that have
different vocalizations or duet structure may in fact be different cryptic
species and that there may be more species than are currently recognized
(Shekelle et al. 1997; Nietsch & Kopp 1998).
Several species of Sulawesian tarsier, including T. dentatus, T. tarsier, and
T. lariang, duet at the end of their activity cycle, before sunrise near the
sleeping site (Niemitz et al. 1991; Tremble et al. 1993; Shekelle 2003; Merker
& Groves 2006). Vocal duets in T. tarsier occur regularly between mated
pairs when they return to the sleeping tree, occurring roughly at the same time
nearly every morning (Gursky 1997, 2000c; MacKinnon and MacKinnon 1980; Nietsch
1999, 2003). In this species, most duets are started by females and last
several minutes (Gursky 2000c; Nietsch 2003). There may be multiple functions
of vocal duets, including territorial displays and mate guarding (Gursky 1997;
2000c; MacKinnon and MacKinnon 1980; Nietsch 2003; Gursky 2007). T. pumilus do
not perform duets when returning to their sleeping site, and may vocalize rarely
(Grow & Gursky-Doyen in review). T. bancanus and T. syrichta do not perform
duets (Nietsch 2003). In fact, wild T. bancanus are not very vocal at all at
some study sites, while at others they are significantly so (Niemitz 1984f;
Crompton & Andau 1987). T. bancanus has been reported to produce "calling
concerts" in which several tarsiers call together, but such events are not
analogous to the duets heard in other tarsiers (Crompton & Andau 1987).
There are a number of types of vocalizations produced by tarsiers that are
not part of duets. For example, T. tarsier has 15 different types of
calls, including distress calls, alarm whistles, alarm calls, mid-intensity
alarm calls, female screams, contact trills, contact whistles, food calls, play
whistles, infant squeaks and other types of whistles (Nietsch 2003). T.
bancanus use four general types of vocalization (Niemitz 1984f).
Several postures in T. tarsier serve a communicatory function. Fear
is communicated by folded ears while a crouched posture, an open mouth, and/or a
lunge forward communicate a defensive threat. A bipedal stance with an open
mouth is an aggressive threat (MacKinnon & MacKinnon 1980).
Tarsiers possess a gland in their lips as well as an abdominal gland, which,
together with the anogenital region, function in olfactory communication when
rubbed on substrates including other tarsiers (Niemitz 1979; MacKinnon &
MacKinnon 1980; Wright et al. 1986; Crompton & Andau 1987; Shekelle 2003).
All tarsiers of various ages and sexes urine mark as well (Niemitz
1979;MacKinnon & MacKinnon 1980). In fact, even if not seen or heard,
tarsiers can be recognized as present in a given habitat purely by their scent
marking alone (Niemitz 1979). T. bancanus of both sexes scent-mark and
vocalize most often during female estrus and proestrus (Wright et al. 1986).
Content last modified: December 1, 2010
Written by Kurt Gron. Reviewed by Nanda Grow.
Cite this page as:
Gron KJ. 2010 December 1. Primate Factsheets: Tarsier (Tarsius) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/tarsier/behav>. Accessed 2013 May 23.