Nilgiri Langur (Trachypithecus johnii)


MORPHOLOGY:
This species has a sacculated stomach to assist in the breakdown of cellulose. The nilgiri langur has enlarged salivary glands to assist it in breaking down food. The dental formula of nilgiri langur is 2:1:2:3 on both the upper and lower jaws (Ankel-Simons, 2000). This species is sexual dimorphic in the canine teeth, where adult males have larger canines than adult females (Poirier, 1969a). The average body mass for an adult male nilgiri langur is around 14.80 kilograms, and for the female it is around 12.00 kilograms (Harvey et al., 1987). Newborns have an average body mass of 0.5 kilograms (Sankhala and Desai, 1969; cited in Roonwal and Mohnot, 1977). The head and body length for males is about 78 centimeters and for females it is about 58.4 centimeters (Parthasarathy, 1995). The pelage color is glossy black with the head being yellowish dark brown in color (Tanaka, 1965). The back of the head is yellowish-brown (Parthasarathy, 1995). The naked skin on the face, ears, forelimbs, and hind legs are black in color (Tanaka, 1965). Females have a white patch on the inside of the thighs that is present in the week-old female (Sunderraj, 2001). The newborn has a reddish-brown pelage color and pale pink skin (Sunderraj, 2001). Newborn hair will begin to turn black at 10 weeks of age (Poirier, 1968a). The infant skin will start to turn to black between two or three months (Poirier, 1968a).

RANGE:
The nilgiri langur is found in the country of India. This species can be found in the states of Madras, Mysore, and Kerala, from the Kanyakumari hills on the southern tip of India to the Coorg Hills in Karnataka, the northern limit of the distribution (Poirier, 1970a; Sunderraj, 2001). Ram and Srinivas (2000/2001) have reported that this species was sighted on a plantation in the Wayanad Plateau near Vayittri. This species is mainly found in sholas, which are narrow tracts of forest with streams running through it (Parthasarathy, 1995; Poirier, 1968b, 1968c; Oates, 1979). This species also lives in semi-evergreen, moist deciduous forests, and montane temperate evergreen forests (Kurup, 1979). The nilgiri langur lives above 900 meters in hilly areas.

ECOLOGY:
The nilgiri langur is a folivorous species, but the diet also includes flowers, buds, seeds, bark, stems, insects, and earth (Roonwal and Mohnot, 1977; Poirier, 1969b; Oates et al., 1980). Poirier (1969b) found that a group would forage for cultivated cabbage, potatoes, and cauliflower and ornamental garden poppies. This species prefers to eat immature leaves over more mature ones. Oates et al. (1980) found that at Kakachi, 45% of the diet came from three tree species. Poirier (1969b) found that the diet can vary from group to group in terms of which foods are favored. Infants will accept new foods whereas adults generally do not (Poirier, 1969b). For example, one group came upon a stand of Eucalyptus globulus, a cultivated plant, and only infants in the group would consume the leaves (Poirier, 1969b). Individuals will eat dirt by either scraping the incisors against the ground or by scraping the soil with their hands, and then rolling the dirt into little balls and then consuming the dirt (Poirier, 1969b). Soil is sometimes collected from termite mounds (Krishnamani and Mahaney, 2000). The nilgiri langur may consume soil to act as an antacid, stabilizing the stomach pH and not causing acidosis (Krishnamani and Mahaney, 2000). The clay in the soil absorbs the fatty acids responsible for decreasing the pH in the stomach (Krishnamani and Mahaney, 2000). Water is obtained directly from eating leaves or from sucking up water from pools or stream through the lips (Roonwal and Mohnot, 1977). The nilgiri langur competes with other mammals for the same food sources, such as the Malabar giant squirrel, the sambar, the barking deer, and cattle (Parthasarathy, 1995). Leaves are eaten by tearing off the sides, exposing the midrib, and then consuming the midrib, which takes about 25-30 seconds (Parthasarathy, 1995). Horwich (1974) found that groups will feed in four to seven feeding bouts, with rests and moving interspersed, throughout the day. Umapathy et al. (1996) found that when habitat size decreases, groups will increase feeding on leaves and decrease feeding on fruits.

On the Mundanthurai Plateau, the diet of the nilgiri langur consists of young leaves (44.06%), mature leaves (4.21%), flowers (8.44%), young fruit (10.51%), ripe fruit (4.59%), seeds (18.61%), and other (petioles, bark, pith, insects, soil, gum, and dead wood) (9.57%) (Sunderraj, 2001). The two most important food species are Derris pinnata and Terminalia bellerica (Sunderraj, 2001). Young leaves are probably preferred because they contain more proteins and less fibre (Sunderraj, 2001). Groups will spend an average of 48.61% of their time feeding (Sunderraj, 2001). Feeding occurs more in the morning and the evening than in the midday (Sunderraj, 2001).

Group sizes range from 3 to 25 individuals. On the Mundanthurai Plateau, the mean group size for the nilgiri langur is 18.5 individuals per group (Sunderraj, 2001). Poirier (1969a) found that the average group size in the Ootacumnd area of the Nilgiri hills, Madras state, was 8.9 individuals. Average group size may be small because of the lack of predators because nilgiri langurs live primarily in the trees (Poirier, 1969a). This is a diurnal and an arboreal species (Parthasarathy, 1995).

The home range of the group depends on the size of the group, with larger groups having larger home ranges (Parthasarathy, 1995; Poirier, 1969b, 1968b, 1968c). Also groups that do not have a preferred food source in their range will have larger home ranges (Roonwal and Mohnot, 1977; Poirier, 1969b, 1968b, 1968c). In areas that have a low abundance of Acacia trees, groups will have larger home range sizes because Acacia provides a year round source of food (Poirier, 1969b, 1968b, 1968c). The home range is also affected by how many neighboring groups are in the area; with groups in densely populated areas have smaller home ranges than those groups in less densely populated areas (Poirier, 1968b, 1968c). Areas that have sleeping sites, resting sites, and preferred food sources are the core areas (Roonwal and Mohnot, 1977; Poirier, 1968b). A group's core area will never overlap the core area of another group, although parts of the home range may overlap (Roonwal and Mohnot, 1977; Sunderraj and Johnsingh, 1998; Poirier, 1968b, 1968c). Groups will spend around 70% of their time in core areas (Poirier, 1968c). Adult females tend to stay in the core areas, where adult males will wander around the home range and even leave the home range at times during intergroup encounters (Poirier, 1968b). Groups will utilize different parts of their home range throughout the year; for example, groups will spent more in area where fruiting Acacia trees are present (Poirier, 1968b, 1968c). Groups will move single file when moving through the trees, each individual passing over the same branches as the preceding one (Roonwal and Mohnot, 1977). Although groups will cross the grassy areas between sholas (Roonwal and Mohnot, 1977; Poirier, 1969b). Groups will utilize the understory of the forest for feeding, resting, and traveling, and the upper story is used for sleeping, morning sunning, and early feeding (Roonwal and Mohnot, 1977). The lower shrub story of the forest is used for morning and afternoon feedings (Roonwal and Mohnot, 1977). The forest floor is utilized for feeding, fighting, escape, and play (Roonwal and Mohnot, 1977). Singh et al. (2000) found that the nilgiri langur is mostly found in medium to lower height trees. Ramakrishnan and Coss (2001) found that nilgiri langurs selected sleeping sites that were near water, away from human settlements, trees with high boles, adult slept higher than subadults, and males slept higher than females. Individuals will sleep away from the main trunk, which could afford them protection from arboreal predators such as the leopard (Ramakrishana and Coss, 2001). If a group must move from their home range, the adult male(s) will move first to the new home range, then the adult females, juveniles, and infants will move to the new home range with the adult male(s) protecting them (Poirier, 1968c). Groups tend to be reluctant to move from their home range and probably only do so under extreme circumstances (Poirier, 1968c). The adult male(s) are generally met with challenges from the resident males of the area they are trying to move to (Poirier, 1968c). Adult males tend to act less nervous during moving than adult females as indicated by their feeding when resting between movement bouts (Poirier, 1968c).

Predators of the nilgiri langur include, dogs (Canis familiaris), leopards (Panthera pardus), and humans (Roonwal and Mohnot, 1977). Humans use the skin for making drums and parts of the body for medicinal uses (Roonwal and Mohnot, 1977; Ramakrishnan and Coss, 2001; Hohmann and Sunderraj, 1990). Lion-tailed macaques, Macaca silenus, have also been known to attack nilgiri langurs (Herzog and Hohmann, 1984).

LOCOMOTION:
The nilgiri langur moves through the forest quadrupedally (Fleagle, 1988). This species will also jump from one branch to another, jumping up to five meters (Tanaka, 1965).

SOCIAL BEHAVIOR:
The nilgiri langur has a unimale social system (Tanaka, 1965). Multi-male groups also are found but are more rare (Roonwal and Mohnot, 1977; Sunderraj, 2001). All male and all females groups have been observed, but all female groups tend to be rare (Parthasarathy, 1995; Sunderraj, 2001; Poirier, 1969a; Hohmann and Sunderraj, 1990). Solitary individuals are also known to occur (Roonwal and Mohnot, 1977; Poirier, 1969a; Tanaka, 1965). Unimale groups are sometimes formed when juvenile males in a group mature to adulthood and then the group fissions into smaller unimale groups (Hohmann, 1989b). Hohmann (1989b) found that group fission would occur with the start of loud call (whoop display) emission by the second mature male in the group. The group that splits off will move away from the founder group (Hohmann, 1989b). Group fission may occur because it could increase the reproductive success of both groups or it could prevent the establishment of solitary or all-male bands that could take over a group (Hohmann, 1989b). Adults are the most numerous individuals in the group (Poirier, 1969a). Both males and females disperse from their natal groups (Sunderraj, 2001). Groups tend to be divided into subgroups that consist of individuals of similar age/or sex class (Roonwal and Mohnot, 1977; Poirier, 1969a). Poirier (1969a) found that most interpersonal relationships occurred within rather than between subgroups. One female will watch many infants while the other females are out foraging (Poirier, 1968a). Adult males and adult females were found to rarely interact with each other (Roonwal and Mohnot, 1977). Adult males tend to remain on the periphery of the group (Roonwal and Mohnot, 1977). Infants and juveniles were not found to interact much with adult males (Parthasarathy, 1995; Roonwal and Mohnot, 1977).

This is a territorial species acting aggressively to conspecific groups. This aggression can vary between different pairs of neighbors (Hohmann and Vogl, 1991; Poirier, 1968b). Poirier (1968b) found that if a group moved the core area to the edge of the home range, then the neighboring group would shift a portion of its home range. When a resident male would spot the resident male of another group, the male would emit grunt which could lead to the whoop display (Poirier, 1968b, 1970a; Tanaka, 1965). The resident male may wait until the group has been in the territory for awhile before commencing the whoop display (Poirier, 1968b). After the resident male stops the vocalization portion of the whoop display, the challenger will reciprocate with the whoop display (Poirier, 1968b). Two males could sometimes perform whoop display simultaneously (Poirier, 1968b). If the whoop display does not make the other group retreat, then the resident male may attack the group to drive them away (Tanaka, 1965). Antagonistic encounters rarely involve physical contact (Poirier, 1968b). Chasing is rare also, but it can sometimes occur on the ground (Poirier, 1968b). When the pursuer would chase the other male into its core area, the roles would reverse and the pursuer would become pursued (Poirier, 1968b). During chasing bouts, defecation and urination are constant not only by the males but also by the other members of each group involved (Poirier, 1968b). Poirier (1968b) found antagonism between groups occurred more following the winter birth peak (January) and immediately preceding the spring birth peak (March and April). Poirier (1968b) found the intergroup encounters often did not occur because of accidental meetings, related to competition for food or water, or related to population overcrowding. Poirier (1968b) believes that antagonistic encounters occur to protect the core area from incursions by neighboring groups and indirectly minimized overfeeding and overcrowding.

A linear hierarchy exists amongst the females in the group. Males also show a linear dominance hierarchy, and most dominance disputes are between adult males (Roonwal and Mohnot, 1977). Males are dominant over females in the group (Poirier, 1970b). Poirier (1970b, 1969a) found that dominance hierarchies are not maintained by fighting, but rather by behavioral patterns (communication), which rarely occur and mostly involve adult males. Dominance interactions tend to occur between individuals of similar ages (Poirier, 1970b). Poirier (1970b) describes the female dominance hierarchy of the nilgiri langur as being stable and well-defined. Adult female dominance interactions tend to include the behavior such as displacement, moving away, looking at, or looking away from (Poirier, 1970b). Embracing also occurs in female dominance interactions, as well as loud vocalizations such as squealing and screeching (Poirier, 1970b). The adult male dominance hierarchy is rigid and well-defined in the nilgiri langur (Poirier, 1970b). The adult male dominance hierarchy is usually maintained by the dominanat individual looking at a subordinate individual (Poirier, 1970b). Lower ranking males will sometimes direct their dominance behavior outside of the male hierarchy to individuals (infants and juveniles) that would mots likely not retaliate (Poirier, 1970b, 1969a). The activity of the group is tied to the activity of the alpha male, i.e. when he stops, the group stops moving (Poirier, 1970b; Tanaka, 1965). Although groups tend not to be male-centered, but rather having a social situation focused on the females (Poirier, 1970b).

The nilgiri langur is sympatric with the lion-tailed macaque, Macaca silenus, in the forests of the Western Ghats of southern India (Singh et al., 2000). Singh et al. (2000) found that there is niche separation between the two species where lion-tailed macaques will spend more time in the lower and upper canopies during the wet season and nilgiri langurs will spend more time in middle canopy level. Lion-tailed macaques also prefer feeding on fruits where nilgiri langurs prefer leaves (Singh et al., 2000). Nilgiri langurs also tend to feed at higher frequency during the afternoon period than lion-tailed macaques (Singh et al., 2000). Lion-tailed macaques will supplant nilgiri langurs from a stratum of the forest, often the langurs will move to a lower level (Singh et al., 2000). Nilgiri langurs do gain from being in an association with lion-tailed macaques because lion-tailed macaques will crack open the hard case of the fruit of Cullenia exharillata, which nilgiri langurs cannot crack open, and if fruit falls out of the hands of a lion-tailed macaque that is already opened, a nilgiri langur can grab and consume the opened fruit (Singh et al., 2000). Nilgiri langurs are also sympatric with common langurs, Semnopithecus entellus, and bonnet macaques, Macaca radiata (Poirier, 1969b).

Social play in the nilgiri langur occurs amongst infants, juveniles, and subadults, and rarely adults (Parthasarathy, 1995). Mothers were found to rarely play with their infants (Roonwal and Mohnot, 1977). Adults will engage in play when the group has no peers for infants or juveniles to play with (Roonwal and Mohnot, 1977). Infants will actively seek out juveniles and subadults for social play (Poirier, 1969a). Adult males may use social play with infants to merge with an established unimale group peacefully (Poirier, 1969a).

VOCAL COMMUNICATION:
pant threat: This is a rapid, low-pitched vocalization consisting of phrases of 4-8 units (Poirier, 1970a; Hohmann, 1989a). This vocalization has little resonance and the lips of the individual emitting this call are rounded (Poirier, 1970a). The head is thrust forward and the mouth is only half to three-quarters open, with the teeth barely visible (Poirier, 1970a). The eyes are wide open, focused on the receiver, with slightly raised eyebrows (Poirier, 1970a). Sometimes the back is arched (Poirier, 1970a). This call is emitted from a static standing or sitting position, and sometimes a slap will accompany this call (Poirier, 1970a). The mean total range of frequency for this call was found to be 5.22 (+/- 2.25) kilohertz (Hohmann, 1989a). The mean duration of this call was found to last 0.18 (+/- 0.12) seconds (Hohmann, 1989a). This is given by adult males during threat sequences or during territorial disputes (Poirier, 1970a; Hohmann, 1989a). This call is also given by nursing mothers towards intruders (Poirier, 1970a).

hiccup: This call is short burst of air sounding like the human, Homo sapiens, hiccup (Poirier, 1970a). During this vocalization the mouth will open slightly and then rapidly close (Poirier, 1970a). The teeth are barely visible (Poirier, 1970a). The head is erect and the eyes are focused on the receiver (Poirier, 1970a). The abdomen pulsates when giving this vocalization (Poirier, 1970a). This is given from a static sitting position and may be given with the back turned towards the stimulus (Poirier, 1970a). The mean total frequency range for this call was found to be 2.80 (+/- 1.64) kilohertz (Hohmann, 1989a). The mean duration of this call lasted 0.06 (+/- 0.02) seconds (Hohmann, 1989a). This serves to communicate nervousness or tension and will occur before or after a threat sequence (Poirier, 1970a). This call is given most often by adult males (Poirier, 1970a). This may be emitted for 10 minutes to 1 hour after a threat sequence or whoop display (Poirier, 1970a). Other members of the group will avoid an individual emitting this vocalization (Poirier, 1970a).

subordinate segmented sound: This is a high-pitched, segmented vocalization, where the mouth is one-fourth open, the upper lip retracted, and some of the upper teeth and sometimes the lips pursed slightly forward (Poirier, 1970a). The lips are drawn into a slight grin when tension increases, which produce creases around the corners of the mouth (Poirier, 1970a). This vocalization is given from a standing or sitting position (Poirier, 1970a). This vocalization serves to communicate submissiveness or appeasement (Poirier, 1970a). During dominance situations it was used as a mild submissive cue, and when used as an appeasement gesture it elicited embrace (Poirier, 1970a).

hollow subordinate vocalization: This low-pitched vocalization is an expiration of air that is produced in staccato-like bursts (Poirier, 1970a). The mouth is one-fourth open and the lips are slightly retracted to reveal the teeth (Poirier, 1970a). This call has an echo-like quality (Poirier, 1970a). This call is given on approach to a dominant individual (Poirier, 1970a). This is an intense submissive call given by adults and subadults (Poirier, 1970a). This is also heard from surprised or startled individuals (Poirier, 1970a). Embrace will usually accompany this call as well as defecation (Poirier, 1970a).

squeal: This is a very high-pitched, uniform, and prolonged vocalization (Poirier, 1970a). This call sounds like a birdcall and is produced with the lips retracted, the tips of the teeth visible, and the mouth one-fourth to one-half open (Poirier, 1970a). The eyes are somewhat downcast, but focused on the receiver (Poirier, 1970a). The head and back are inclined forward, with the legs slightly flexed when standing (Poirier, 1970a). The mean total range of frequency for this call was found to be 6.79 (+/- 2.87) kilohertz (Hohmann, 1989a). The mean duration of this call lasted 0.22 (+/- 0.13) seconds (Hohmann, 1989a). This call is given by adult and subadult females (Poirier, 1970a; Hohmann, 1989a). Hohmann (1989a) also found that immature males will emit this vocalization when attempts at physical contact were rebuffed. Embracing, presenting, and head shaking will accompany this call (Poirier, 1970a). This is a submissive call given during intense threat sequences (Poirier, 1970a).

screech: This is a very high-pitched, nontonal, shrill, and prolonged vocalization that consists of rapid expirations (Poirier, 1970a). The lips are retracted, more so as compared to squeal, with the tips of the teeth showing (Poirier, 1970a). The mouth is one-half to three-fourths open and the tongue is retracted, resting on the soft palate (Poirier, 1970a). The sender stares at the receiver, with the head and torso inclined forward (Poirier, 1970a). In a sitting position, the body is reduced with the limbs pressed against the body and the torso lowered (Poirier, 1970a). There is variation in pitch when this given over a long period (Poirier, 1970a). Presenting, spasmodic limb movements, and defecation will accompany this vocalization (Poirier, 1970a). The feces are characteristically soft and fetid (Poirier, 1970a). This is the most intense submissive vocalization (Poirier, 1970a, 1970b). This is emitted by individuals of all ages and both sexes (Poirier, 1970a). If the recipient starts to chase or gives an intention movement, the sender will rapidly flee (Poirier, 1970a). The reduced posture may make the individual less vulnerable to an attack (Poirier, 1970a).

grunt: This is a deep guttural call of short duration (Poirier, 1970a). The mouth is slightly open with the teeth barely showing (Poirier, 1970a). This call is emitted from a static or moving posture (Poirier, 1970a). The mean total range of frequency for this call was found to be 8.12 (+/- 3.67) kilohertz (Hohmann, 1989a). The mean duration of this call lasted 0.07 (+/- 0.03) seconds (Hohmann, 1989a). This is emitted by adults and will elicit similar vocalizations (Poirier, 1970a). Hohmann (1989a) found that subadult males and females would also emit this call. This call serves to facilitate group cohesion (Poirier, 1970a). Adult males will also emit this when returning from a territorial dispute (Poirier, 1970a). This call is also heard during agonistic situations, at the end of a threat sequence, and during territorial battles (Poirier, 1970a, 1970b). Adult males will give this call when approaching females to gain social contact (Hohmann, 1989a). Females will give this call in response to the sudden approach of a male and when embracing another female (Hohmann, 1989a).

gruff bark: This is a violent expulsion of air that is produced by rapidly opening the mouth (Poirier, 1970a). The abdomen of the sender will pulsate (Poirier, 1970a). This is composed of abrupt, low frequency, high amplitude phrases that consist of alternating audible inhalations and exhalations (Poirier, 1970a). The mean total range of frequency for this call was found to be 10.64 (+/- 2.90) kilohertz, except when uttered in the presence of a leopard, and then it changed to 11.44 (+/- 2.05) kilohertz (Hohmann, 1989a). The mean duration of this call lasted 0.11 (+/- 0.03) seconds, and in the presence of a leopard it was 0.10 (+/- 0.01) seconds (Hohmann, 1989a). This call is emitted by adults when presented with a danger to the group, such as dogs (Canis familiaris), wild dogs (Cuon alpinus), leopards, jackals (Canis aureus), and humans (Poirier, 1970a; Hohmann, 1989a). This call is also directed at non-predators such as strange conspecifics, bonnet macaques (Macaca radiata), squirrels (Funambulus palmarum and Ratufa indica), and deer (Axis axis and Cervus unicolor) (Hohmann, 1989a). Tense mothers will also emit this towards strange humans (Poirier, 1970a). The closer the proximity of the danger, the intensity of the call will increase, the number of units per call will increase, and the interval between phrases will decrease (Poirier, 1970a). Whoop display or hoho will be heard between barks sometimes (Poirier, 1970a). If there is a predator, all group movement will cease, the focus is shifted towards the predator, and the vocalizing individual will move to position above the predator (Poirier, 1970a). Infants will run to their mothers when one member of the group emits this call (Poirier, 1970a). This call can last up to fifteen minutes after the danger has left (Poirier, 1970a). Surrounding groups that hear another group's gruff barks will sometimes respond with hiccups (Poirier, 1970a).

alarm or warning call: This is a very high-pitched and prolonged vocalization where the mouth is one-fourth to one-half open and the lips slightly retracted (Poirier, 1970a). The attention is focused on the receiver (Poirier, 1970a). The back and limbs are held tense (Poirier, 1970a). This vocalization is emitted from a standing or sitting position (Poirier, 1970a). This is emitted in tension situation and has the same function as gruff bark (Poirier, 1970a). All activity in the group will cease, and this call will attract the attention of nearby groups (Poirier, 1970a). This was found to emitted more frequently by adult females than by adult males (Poirier, 1970a).

whoop display (loud call): This is a loud, sonorous, and prolonged violent expiration of air given through rounded lips (Poirier, 1970a). The onset of this call is characterized by a violent rasping inspiration of air (Poirier, 1970a). The abdomen will pulsate during the emission of this call (Poirier, 1970a). This vocalization is emitted from a static standing or sitting posture (Poirier, 1970a). There are tonal differences, which can be used to identify individuals emitting this call (Poirier, 1970a). After the first frames of this call, there is a pause where the tail hangs over the back; there is individual variation in the duration of the break (Poirier, 1970a). The mean total frequency range for the exhalation phase was found to be 4.15 (+/- 3.29) kilohertz and for the inspiration phase it was 1.07 (+/- 0.92) kilohertz (Hohmann, 1988). The mean duration of the expiration phase was found to be 0.13 (+/- 0.05) seconds, the inspiration phase lasted 0.13 (+/- 0.04) seconds, and the interval between the two phrases was found to be 0.08 (+/- 0.09) seconds (Hohmann, 1988). Hohmann and Vogl (1991) found that loud call bouts contained anywhere from 1 to 22 phrases and having an average of 48 units per bout. There are six different types of units that can comprise a loud call: whoop, ho-ho, hiccup, pant barks, cough barks, and harsh barks (Hohmann and Vogl, 1991). Herzog and Hohmann (1984) found that there are two types of loud calls: type 1, which is composed of heterogeneous, irregular, two-phasic, nontonal units, "ha-ah" and "hoo" sounds. Type 2 consists of homogeneous compound units composed of a tonal exhalation phase and softer, noise-like inhalation phase (Herzog and Hohmann, 1984). In type 2, the energy in both phases is concentrated on the fundamental frequency (Herzog and Hohmann, 1984). This call is only given by the resident adult male of the group (Poirier, 1970a; Hohmann, 1991; Tanaka, 1965). A male's loud call will sometimes change over the course of a lifetime, increasing the number of units per bout (Hohmann and Vogl, 1991).

There is also a motor component to this display where males will also jump between branches in trees in a taut, heavy manner that produces a large amount of noise (Poirier, 1970a; Hohmann, 1989a; Tanaka, 1965). One type of jump, termed a "rotation jump" by Hohmann and Vogl (1991), is where the individual will start from a sitting position, moves forward, and then jumps, where the body makes a horizontal rotation (Hohmann and Vogl, 1991). The individual will land with the head towards the branch, showing the pink and white rump (Hohmann and Vogl, 1991). Jumping will occur between dry and brittle branches that will break and snap on impact, producing as much noise as possible (Poirier, 1970a). Elements of the jumping with rotating are seen in infants and juveniles (Hohmann and Vogl, 1991). This call is elicited by the sight of adjacent groups, the falling of a tree, the beeping of a horn, and during intergroup dominance sequences (Poirier, 1970a). Males will also do this in response to other males' whoop display (Poirier, 1970a). During the morning, males will give this call from the treetops, but without the characteristic jumping and other movements (Poirier, 1970a). Groups males will respond to other group males' morning whoop calls (Poirier, 1970a). The morning call could serve to avoid inter group contact, thus territorial battles (Poirier, 1970a).

Horwich (1974) describes the onset of this call as being a series (15-17) of "hoo" sounds. After the onset of this call, the individual emitting this call will be in a quadrupedal stance with the arms bowed, rump raised, and the tail looped over the back and head (Horwich, 1974). After this pause, there is an emission of slower "hoos" preceded by a series of sounds that sound like "HAH-ah-HAH-ah" caused by a violent expiration of air (Horwich, 1974). At this time the individual will also leap forward, making much noise when moving between trees (Horwich, 1974). Twenty to sixty seconds later, a series of four slow "hoos" are emitted while sitting on a branch (Horwich, 1974). This is followed by another series of four slow "hoos" and occasionally a "kak" or a "haha" sound is interspersed between them (Horwich, 1974). Horwich (1974) found that whoop display occurs more frequently on days that are cloudy and misty.

hoho: This call is similar to the one given during whoop display, although it is less resonant, the frames shorter, and it is more staccato (Poirier, 1970a). The lips are rounded and this call is given from a standing, sitting, or running posture (Poirier, 1970a). The mean total range of frequency for this call was found to be 2.02 kilohertz (Hohmann, 1989a). The mean duration of this call lasted 0.10 seconds (Hohmann, 1989a). Both adult males and females will emit this call (Poirier, 1970a). Hohmann (1989a) found that juveniles and subadults of both sexes would emit this call during playful chase bouts. The female version of this call is less tonal and less loud as compared to the male version (Hohmann, 1989a). Running and jumping through trees will accompany this vocalization (Poirier, 1970a). This call is elicited by and used in the same situations as whoop display (Poirier, 1970a).

canine grind: This sound emission is produced by slowly rubbing the canine teeth together (Poirier, 1970a). The head is thrust slightly forward and eyes staring at the receiver (Poirier, 1970a). This sound emission is produced from static positions (Poirier, 1970a). This is heard during intra- and intergroup encounters (Poirier, 1970a). Only adult males will produce this sound emission (Poirier, 1970a; Hohmann, 1991). This will sometimes follow threat or attack sequences for a duration of up to 20 minutes (Poirier, 1970a).

warble: This is a deep, hollow sound that sounds like subordinate segmented vocalization (Poirier, 1970a). The mean total range of frequency for this call was found to be 6.10 (+/- 2.94) kilohertz (Hohmann, 1989a). The mean duration of this call lasted 0.64 (+/- 0.24) seconds (Hohmann, 1989a). This is given by the mother to her infant, and the infant will respond by clinging to the mother (Poirier, 1970a). Hohmann (1989a) found that this call is emitted by all age/sex classes.

whistle: This is a call of tonal or mixed units having a high frequency modulation (Hohmann, 1989a). This call contrasts with warble by having a frequency modulation that is less regular and having energy distributed over a wider range (Hohmann, 1989a). The mean total range of frequency for this call is 10.29 (+/- 2.83) kilohertz and the mean duration is 0.34 (+/- 0.22) seconds (Hohmann, 1989a). This is heard from adult and subadult females, juveniles, and infants (Hohmann, 1989a, 1991). Adult females will utter this vocalization when adult males perform the jumping and chasing components of whoop display in connection with agonistic encounters with other groups (Hohmann, 1989a). Adult and juvenile females will also emit this when harassing a mating pair and when approaching and embracing an infant (Hohmann, 1989a). Infants will emit this when their attempts for physical contact are rebuffed and when females approach and embrace them (Hohmann, 1989a). Hohmann (1991) found that this was the call uttered most frequently by individuals.

squeak: This is a high-pitched, grating sound where the mouth is barely open (Poirier, 1970a). This composed of long drawn-out phrases that are continuously repeated at about the same pitch level (Poirier, 1970a). With increased tension, the mouth will open more and the pitch level will rise (Poirier, 1970a). This call is emitted from a standing or sitting position (Poirier, 1970a). This is given by infants and juveniles (Poirier, 1970a). This is given in situations of tension or excitement (Poirier, 1970a). This given when the infant is separated from the mother, and if the mother does not respond, the infant will exhibit a temper tantrum (Poirier, 1970a). This call is long and drawn-out when infant and mother are separated, and segmented, variable in tone, and lower in pitch when infant and mother are reunited (Poirier, 1970a).

scream: This is a shrill, high-pitched, nontonal, and prolonged vocalization (Poirier, 1970a). The lips are retracted and the mouth is one-half open (Poirier, 1970a). This is emitted by the infant who looks at the mother while vocalizing (Poirier, 1970a). When emitted from a sitting position, spasmodic limb movements will accompany this call (Poirier, 1970a). Frenetic running often accompanies this call (Poirier, 1970a). This is primarily a weaning vocalization (Poirier, 1970a). This is heard by an infant when the mother will rebuff the attempts to nurse (Poirier, 1970a). Hohmann (1989a) refers to this call as wailing.

growl: This call consists of rapid, repetitive, soft, short, and low frequency sounds (Poirier, 1970a). This is emitted during agonistic encounters (Poirier, 1970a).

roar: This a harsh vocalization heard during intergroup encounters (Poirier, 1970a). This sounds like the clearing of the throat (Poirier, 1970a).

chuckle: This is a segmented, high-pitched, and modulated vocalization (Poirier, 1970a). This was heard by an adult female when a male slapped her (Poirier, 1970a).

OLFACTORY COMMUNICATION:
mouth sniffing: An individual will lean forward and stare at the receiver, and orients the nose towards the receiver's mouth (Poirier, 1970a). The nose will sometimes touch the mouth of the receiver (Poirier, 1970a). The behavior is usually found during feeding (Poirier, 1970a). This behavior is performed by both sexes of all age classes (Poirier, 1970a). Dominant individuals will sniff the mouths of subordinates and equals will sniff each other's mouths (Poirier, 1970a).

VISUAL COMMUNICATION:
look threat: This is when the eyes are wide open and oriented towards the receiver (Poirier, 1970a). This behavior may be performed from a sitting or standing position (Poirier, 1970a). The head may be inclined forward when performing this behavior (Poirier, 1970a). The duration of this behavioral pattern is described as being short (Poirier, 1970a). This is performed by adults, subadults, and juveniles of both sexes (Poirier, 1970a). This is used to communicate a mild threat (Poirier, 1970a). The receiver will usually respond by looking away (Poirier, 1970a).

stare threat: This is when an individual has the eyes wide open and oriented towards the receiver (Poirier, 1970a). The eyebrows are slightly raised causing creases to form on the forehead (Poirier, 1970a). The head is inclined towards the receiver and is lowered towards the chest (Poirier, 1970a). The back is inclined 5-7 degrees and there is an associated raising of the hindquarters (Poirier, 1970a). The mouth is usually closed, but sometimes the mouth is open when given from a standing or sitting position (Poirier, 1970a). This is performed by adults and subadults of both sexes (Poirier, 1970a). This behavior serves to communicate threat, stronger than that found with look threat (Poirier, 1970a). The receiver of this behavior will usually look away and then move (Poirier, 1970a).

head bob: This is when an individual will stare at another and rapidly bob the head in a vertical plane (Poirier, 1970a). The mouth is open, frequently, but the teeth are rarely showing (Poirier, 1970a). Creases show on the forehead and the shoulders slightly dip when the head moves (Poirier, 1970a). This display is given from a static standing position (Poirier, 1970a). The limbs are slightly tensed (Poirier, 1970a). This display serves to communicate threat and is an intensification of stare threat (Poirier, 1970a). Receivers of this behavioral pattern will usually respond with present (Poirier, 1970a).

open mouth threat: The sender has the eyes wide open and focused on the receiver (Poirier, 1970a). The mouth is wide open, but the lips are not retracted and the teeth are barely showing (Poirier, 1970a). The mouth has an elliptical shape that exposes red gums and the tongue (Poirier, 1970a). The head and torso are moved forward towards the receiver (Poirier, 1970a). This is performed by adults, subadults, and juveniles of both sexes (Poirier, 1970a). This display will often precede a more intense threat gesture (Poirier, 1970a). A dominant individual will direct this towards a subordinate individual (Poirier, 1970a). The subordinate will most often respond with present (Poirier, 1970a).

chase: This is a threat gesture performed by adults, subadults, juveniles, and infants of both sexes (Poirier, 1970a). The recipient responds by running away (Poirier, 1970a).

biting air: This is when an individual will stare at the receiver, incline the head forward, and retract the lips slightly to expose the teeth (Poirier, 1970a). The mandible opens and closes, resulting in an exaggerated bite (Poirier, 1970a). There are slight head movements in the vertical plane when the mouth is opened and closed rapidly (Poirier, 1970a). This display is performed from a standing or sitting position (Poirier, 1970a). The limbs are tensed and one of the forearms is thrust towards the receiver (Poirier, 1970a). This is performed by adults and subadults of both sexes (Poirier, 1970a). This is an intensification of open mouth threat (Poirier, 1970a). The sender will sometimes charge the receiver, and grunt will sometimes occur if the sender is nervous (Poirier, 1970a). This is given by a dominant individual towards a subordinate one (Poirier, 1970a).

look away: This is when the eyes are turned from the stare of a more dominant individual by turning the head to the side or looking in the other direction (Poirier, 1970a). The mouth is closed during the behavior (Poirier, 1970a). This behavior is done in response to look threat or stare threat (Poirier, 1970a). This is performed by adults, subadults, juveniles, and infants of both sexes (Poirier, 1970a).

head shaking: This is when an individual will laterally rotate the head rapidly in the horizontal plane (Poirier, 1970a). The mouth may be opened or closed, and the teeth are sometimes shown (Poirier, 1970a). The individual will look away from the recipient of this behavior, looking down at the ground (Poirier, 1970a). The back is inclined forward slightly and the hindquarters are raised (Poirier, 1970a). This behavior is performed from a static standing position (Poirier, 1970a). If this behavior becomes intense, the hindquarters will be directed towards the receiver (Poirier, 1970a). This behavioral pattern is performed by both adult males and females (Poirier, 1970a). This is a submissive gesture done in response to an intense threat from a more dominant individual (Poirier, 1970a).

grin: This is when an individual will have the eyes wide open and focused on the receiver (Poirier, 1970a). The mouth is 50-75% open and the corners are retracted to reveal teeth that are occluded or partially open (Poirier, 1970a). Tension creases are form across the cheeks (Poirier, 1970a). The individual will thrust the head forward towards the receiver (Poirier, 1970a). The limbs are rigid and this is done from a standing or sitting position (Poirier, 1970a). This display serves to communicate threat on the part of the sender, used to assert dominance over lower ranking individuals (Poirier, 1970a). This is performed by adult males and females (Poirier, 1970a). This display is sometimes intensified by a grunt (Poirier, 1970a).

yawn: This is when an individual will open the mouth slowly and retract the lips baring the teeth (Poirier, 1970a). The head of the individual is pulled back on to the shoulders (Poirier, 1970a). The performer of this behavior will stare into the air or have the eyes closed (Poirier, 1970a). This behavioral pattern is performed from a sitting position (Poirier, 1970a). This may serve to indicate a state of weariness (Poirier, 1970a).

gamboling: This is a playful walk consisting of a "bouncy" form of locomotion (Poirier, 1970a). The hind legs will be kicked into the air when performing this behavior (Poirier, 1970a). This serves to communicate a playful mood (Poirier, 1970a). This is performed by subadults, juveniles, and infants of both sexes (Poirier, 1970a).

play invitation: This is where the mouth is open, and is done by subadults, juveniles, and infants of both sexes (Poirier, 1970a). The recipient will respond with playing (Poirier, 1970a).

present: This is when an individual will orient the rump towards the receiver with the tail dropped (Poirier, 1970a). The head is directed away from the receiver, but sometimes the sender will look at the receiver (Poirier, 1970a). The body is inclined forward with the forelimbs slightly flexed and the hindquarters elevated (Poirier, 1970a). This behavior is performed from a static standing position (Poirier, 1970a). Head shaking will sometimes accompany this behavior (Poirier, 1970a). This behavior is performed by a subordinate individual (Poirier, 1970a). This is done from within a few feet of the receiver (Poirier, 1970a). This is performed by adults, subadults, juveniles, and infants of both sexes (Poirier, 1970a). This behavior can function to prevent the attack from a more dominant individual, to placate a more dominant individual, or to win the favor of the recipient to sit close and feed or to groom (Poirier, 1970a, 1970b).

rear end flirtation: This is where an individual will walk by another with the limbs slightly flexed, and then turn the hindquarters when passing the other individual (Poirier, 1970a, 1970b). This is given by a subordinate individual to a more dominant one, and if the dominant individual would ignore the signal, the sender will continue with this walk (Poirier, 1970a). This display is a variation of present (Poirier, 1970a).

freezing: This is where an individual will be in a sitting posture, with the body inclined forward and the lumbo-sacral region rigid (Poirier, 1970a). The head is upright, but staring away from the stimulus (Poirier, 1970a). The mouth is closed and the forearms are straight and rigid with the palms down (Poirier, 1970a). This is performed by adults, subadults, juveniles, and infants of both sexes (Poirier, 1970a). This display is a subordinate gesture (Poirier, 1970a). This behavioral pattern is most often seen during feeding where a dominant individual approaches a subordinate and the subordinate freezes (Poirier, 1970a).

displacement: This is when a subordinate individual will move away from a position near a dominant individual (Poirier, 1970a). This is performed by adults, subadults, and juveniles of both sexes, although it is rare in juveniles (Poirier, 1970a). The sender may present before leaving (Poirier, 1970a). This behavioral pattern communicates submission (Poirier, 1970a).

lunge in place: This is when an individual will move the body forward in a rapid motion (Poirier, 1970a). The eyes are wide open and staring at the stimulus with a rigid body and limbs (Poirier, 1970a). The back is slanted slightly forward and the hindquarters are raised (Poirier, 1970a). One or both of the forelimbs are directed at the receiver and pant will accompany this behavior (Poirier, 1970a). This is an intense dominant gesture seen during intra- and inter-group agonistic situations (Poirier, 1970a). The response is usually an intense submissive gesture (Poirier, 1970a).

genital inspection: This is when one individual will visually or manually and visually inspect the genitals of another (Poirier, 1970a). This is performed by adults and subadults of both sexes (Poirier, 1970a). This behavior is either a dominance-subordinance act or greeting behavior (Poirier, 1970a).

standing over: This done by the mother to her infant and signals to the infant that they can cling to the mother (Poirier, 1970a). The infant will respond with clinging to the mother (Poirier, 1970a).

approach towards: This done by the mother to her infant and signals to the infant that they can cling to the mother (Poirier, 1970a). The infant will respond with clinging to the mother (Poirier, 1970a).

outstretched hand: This done by the mother to her infant and signals to the infant that they can cling to the mother (Poirier, 1970a). The infant will respond with clinging to the mother (Poirier, 1970a).

TACTILE COMMUNICATION:
bite: This has been seen to occur during wrestling bouts (Poirier, 1970a). This is performed by adults, subadults, and juveniles of both sexes (Poirier, 1970a).

mounting: This is when an individual will approach another who is standing on four limbs from behind, grasping the waist with the hands and gripping the legs with first and second phalanges of the hind feet (Poirier, 1970a). Then pelvic thrusts may be given, usually less than six (Poirier, 1970a). Sometimes the mounted individual will grasp one of the hind legs of the mounter, and sometimes the mounted individual will turn its head to face the mounter (Poirier, 1970a). The mounter will sometimes lean forward and cover the back of the mounted individual (Poirier, 1970a). The mounter may also mouth the vertebral column of the mounted individual (Poirier, 1970a). This behavior ends when the mounter dismounts, and social grooming may follow, with usually the mounted grooming the mounter (Poirier, 1970a). The mounter is usually a dominant individual (Poirier, 1970a). When the mounted individual is sitting or lying down, pelvic thrusts will be directed towards the back (Poirier, 1970a). This is performed by adults, subadults, juveniles, and infants of both sexes (Poirier, 1970a).

mouthing: This is an exaggerated form of bite (Poirier, 1970a). The lips are retracted, which expose the teeth (Poirier, 1970a). The teeth will grasp, but the skin is not broken of the receiver (Poirier, 1970a). After the teeth have grasped, sucking movements are performed (Poirier, 1970a). This is seen during play behavior and as a terminal cue in mounting (Poirier, 1970a). The mounting individual will lean over the back of the mounted individual and mouth along the vertebral column before dismounting (Poirier, 1970a).

face licking: This is when an individual will lick the buccal region of another (Poirier, 1970a). The eyes of the sender will stare at or look near the eyes of the receiver (Poirier, 1970a). This behavior may be a subtle dominance-submissive interaction (Poirier, 1970a). This behavior may be either correlated with or a variation of mouth sniffing (Poirier, 1970a).

touching: This is when one individual will place one hand on either the back or a limb, staring at the recipient (Poirier, 1970a). This behavior is done from either a sitting or standing position (Poirier, 1970a). This is either used as a mild assertive gesture, given by a dominant individual to a subordinate, or a signal that an agonistic episode has ceased (Poirier, 1970a). The assertive type touch may be an abbreviated form of mounting (Poirier, 1970a). After the comfort type touching, the recipient will usually become relaxed (Poirier, 1970a). This is performed by adults, subadults, juveniles, and infants of both sexes (Poirier, 1970a).

slap at: This is when an individual will rapidly thrust a forelimb at another individual (Poirier, 1970a). The hand is open and oriented in the vertical axis when performing this behavior (Poirier, 1970a). The slap often misses the intended mark, which is usually the neck, shoulder region, or limbs (Poirier, 1970a). Staring and open mouth threat will often accompany this behavior, and when this becomes intense, pant may be emitted (Poirier, 1970a). This behavior is dome from either a sitting or a standing position (Poirier, 1970a). This is performed by adults, subadults, juveniles, and infants of both sexes (Poirier, 1970a).

ventro-ventral embrace: This is when two individuals will face each other with their forelimbs wrapped around each other (Poirier, 1970a). The dominant individual will initiate this behavior by extending an arm (Poirier, 1970a). The subordinate individual will bury the head in the chest or shoulder of the dominant individual, and will perform slight head movements in the horizontal plane (Poirier, 1970a). Mouthing and submissive vocalizations, like hollow subordinate sound, will accompany this behavior (Poirier, 1970a). This behavior serves to pacify one or both participants (Poirier, 1970a).

pat on back: This is done by adult females towards their infants, and it is a signal of impending movement (Poirier, 1970a). The infant will respond by clinging tightly to the mother (Poirier, 1970a).

social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals. Grooming is done by using the hands to move the hairs and pick out dead skin and parasites (Parthasarathy, 1995). Grooming bouts may last from 1-23 minutes, and occur most often in the afternoon (Roonwal and Mohnot, 1977). Most social grooming bouts concentrate on the areas of the body an individual cannot reach when self-grooming: back, head, neck, shoulders, and base of the tail (Roonwal and Mohnot, 1977). Adult females were found to groom more than adult males, and adults will rarely groom juveniles and infants (Parthasarathy, 1995; Poirier, 1969a). Dominant individuals are groomed more than subordinate ones (Parthasarathy, 1995). Most grooming was found to occur on sunny days (Parthasarathy, 1995).

wrestle: This is done by adults, subadults, juveniles, and infants of both sexes, and communicates a willingness for rough play (Poirier, 1970a). The recipient will respond with play (Poirier, 1970a).

REPRODUCTION:
The nilgiri langur gives birth to a single offspring. During estrus the clitoris of the female becomes dark pink and more pronounced (Roonwal and Mohnot, 1977; Hrdy and Whitten, 1987; Parthasarathy, 1995). Poirier (1968a) found that the primary birth season occurs in May and June, and second birth season occurs in November. On the Mundanthurai Plateau, birth peaks were found in the months of May and November (Sunderraj, 2001). These birth peaks could coincide with the growth of fresh leaf sprouts that follow the monsoons, thus a time of greater food availability (Sunderraj, 2001). The nilgiri langur may be able to hybridize with the hanuman langur, Semnopithecus entellus, this based on whoop call structure (Hohmann, 1988).

Groups will move less and more slowly when there is a birth in the group (Poirier, 1968a). Females with infants will generally form a subgroup because they tend to feed and move less frequently than other group members (Poirier, 1968a). Females tend to have weak bonds with their infants, expressed in their protective attitude (Poirier, 1969a). These weak bonds may influence the weak social organization of the nilgiri langur group (Poirier, 1969a). Poirier (1968a) did find the bonds between mother and infant are strongest when the infant is at the reddish-brown color phase. Mothers will carry their young ventral-ventral, meaning on their stomach, when they are moving through the trees (Poirier, 1968a). When rain falls, the mother will place the back to the rain to protect the infant and provide warmth (Poirier, 1968a). Infants will leave their mothers to explore at three to four weeks (Poirier, 1968a). Other members of the group will often ignore an infant that is distressed even when the infant is vocalizing (Poirier, 1968a). Poirier (1968a) found the transferring infants between adult females had a high frequency when the infant was three weeks of age, but stopped after the infant reached seven weeks. Infant transferring allows the mother to fed more freely, especially in the shrub level where predators are more prevalent (Poirier, 1968a). Poirier (1968a) found that infant transferring in the nilgiri langur was not related to hierarchy. An adult female may have watch over two or three infants at one time (Poirier, 1968a). Infants will begin weaning at nine weeks when they begin to eat solid food (Poirier, 1968a). During the early stages of weaning, the mother will alternate between accepting and rejecting her infant (Poirier, 1968a). When the infant reaches ten to eleven months of age, the mother will harshly reject the infant when it attempts to nurse (Poirier, 1968a). Rejection methods include slapping and biting (Poirier, 1968a). Weaning ends when the infant is about one year old (Poirier, 1968a). Juveniles will maintain a close relationship with their mothers if the mothers allow (Poirier, 1968a). Adult males generally avoid the mother-infant pair, moving away if a young infant approaches too close (Poirier, 1968a). Poirier (1968a) notes that social grooming and social play rarely occur between infant and mother.

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Last Updated: June 20, 2007.
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