Group composition,home range,and diet of the maroon leaf monkey (Presbytis rubicunda) at Tanjung Puting Reserve,Central Kalimantan,Indonesia

Maroon leaf monkeys (Presbytis rubicunda) were studied at the Orangutan Research Conservation Project study area at the Tanjung Puting Reserve in Central Indonesian Borneo for approximately 15 months in 1974, 1975, and 1977. Over 250 observation hr involving 300 encounters with the monkeys were logged. Troop size ranged from three to eight individuals in the nine troops surveyed with only one adult male being present in each troop. Home range size varied from 0.33 km² to 0.99 km² and correlated with troop size. Forty-six different food types were observed eaten by the maroon leaf monkeys; of these foods, 52% consisted of fruits, 36% of leaves, and 12% of flowers.     

Twins in free-ranging Hanuman langurs (Presbytis entellus)

Two pairs of twins were observed in free-ranging Hanuman langurs (Presbytis entellus) at Jodhpur, India. Each twin had a preferred nipple for suckling, the preference of which developed during the first 5 weeks of life. The behaviour of the twins was mostly synchronized. In more than 60% of all activity bouts both showed the same behaviour, with “nipple contact” and “playing” prevailing. Differences in physical strength and development were apparent within each pair. While the total amount of allomothering was almost the same, individual weekly scores differed considerably.     

Pubic symphyseal synostosis and sexual dimorphism of the pelvis inPresbytis cristata andPresbytis rubicunda

This study examines the relationship between public symphyseal synostosis and sexual dimorphism of the pelvis in two sympatric species ofPresbytis—P. cristata andP. rubicunda. Whereas no specimen ofP. cristata shows fusion of the interpubic joint, a high percentage of female (43.8%) and male (83.3%)P. rubicunda have a fused public symphysis. As females of both species are similar in body size, they are predicted to give birth to similarly sized newborns. Based on comparison with other anthropoids, the percentage dimorphism in the ischiopubic index inP. cristata andP. rubicuda suggests selection on pelvic capacity in relation to obstetrics. In species characterized by cephalopelvic constriction (i.e., the size of the fetal cranium closely approximates the capacity of the maternal birth canal), successful birth seems possible only by a hormonally induced increase in pelvic joint mobility during delivery. However, fusion of the interpubic joint obviates pelvic joint mobility. Consequently, this study tests the hypothesis thatP. rubicunda shows obstetric adaptations of the pelvis that are not found inP. cristata. The results show that pelvic capacity is larger in females than males in bothP. cristata andP. rubicunda; the sexual difference is most pronounced at the inlet. Moreover, the pattern of pelvic dimorphism is nearly identical between the species. When females of the two species are compared,P. rubicunda evidences a shorter distance between the sacroiliac and hip joints and a wider bituberous diameter. The former is related to interspecific differences in locomotion, and the latter is associated with obstetrics.     

Food selection by two South-east Asian colobine monkeys (Presbytis rubicunda and Presbytis melalophos) in relation to plant chemistry

The diets of the banded leaf monkey ( Presbytis melalophos ) at Kuala Lompat in the Krau Game Reserve of West Malaysia and the red leaf monkey ( Presbytis rubicunda ) in Sepilok Virgin Jungle Reserve, Sabah, East Malaysia have been examined in relation to plant chemistry. Both monkeys spent about half their time eating foliage, and about half their time eating fruits and seeds. They both favoured leaves with high digestibility (due to relatively low levels of fibre) and high levels of protein, a combination found predominantly in young leaves and some flowers. The monkeys appeared to favour seeds and fruits with high concentrations of storage carbohydrates or fats, but not those rich in simple sugars. Selection of seeds and fruits was not correlated with protein content.
An analysis of the fibre and protein contents of foods showed that, on an annual basis, the two monkeys achieved a comparable intake for both items. However, these diets were obtained in radically different ways. Presbytis melalophos was able to eat foliage from many of the common tree species in its home range, whereas P. rubicunda relied on rare trees and lianas. This difference is attributed to the very high density of Dipterocarpaceae at Sepilok, a tree family that provides little food for colobines. The rarity of P. rubicunda's food plants at Sepilok is considered to be the main reason for the greater home range size and lower population density in comparison to P. melalophos.
Finally, the biochemical profiles of the young leaf diet of these two monkeys were compared with previously published information on two African and one south Indian colobines. In many respects the intake of supposed critical components, protein and fibre, showed marked similarities between different animals, considering contrasts in their habitats.     

Birth spacing in langur monkeys (Presbytis entellus)

This paper presents 10 years of reproductive data on birth interval length and 5 years of data on reproductive behavior postpartum from a captive colony of gray langur monkeys (Presbytis entellus)housed in Berkeley, California. Birth intervals of females following different pregnancy and nursing schedules are compared. Females whose infants survive to the age of 9 months have a median birth interval of 15.4 months. The experimental separation of mothers from infants for a period of 2 weeks, 6 to 9 months postpartum, had no significant effect on the median birth interval length. Females experiencing a pregnancy failure or the loss of a neonate had median birth intervals of 9.6 and 10.7 months, respectively. These intervals were significantly shorter than the birth intervals of females whose infants survived to 9 months, showing that the presence of a nursing infant delays the female’s time to next conception by approximately 5 to 6 months. Females experienced a median of three estrous periods (two estrous cycles) before conceiving postpartum, regardless of pregnancy outcome or length of infant survival, and females rarely conceived during their first estrous period postpartum. Weaning did not occur until after the mother’s next conception. These data indicate that, in populations of langurs characterized by average birth intervals of 15 to 16 months, the loss of an infant after the age of 5 to 6 months will not accelerate a female’s ability to conceive or shorten the birth interval length. The available data on birth spacing from populations of free-ranging langurs are reviewed. It could not be demonstrated that non-Himalayan populations are characterized by birth intervals which are as long as 20 to 24 months. Rather, it is suggested that female langurs inhabiting seasonally arid sites, such as Jodhpur, Abu, and Dharwar, may be capable of producing infants on the average of every 15 to 16 months. Flexibility in the timing of births and the lack of well-defined birth seasons at these sites may be explained by this species’ dietary and digestive adaptations. Additionally, data on birth spacing and the age of missing infants from the above field sites, where it has been suggested that infanticide following changes in male leadership occurs habitually, do not lend support to the sexual selection hypothesis of infanticide as proposed by S. Hrdy (1974, 1977).     

Social stability and change among forest hanuman langurs (Presbytis entellus)

The social organization of hanuman langurs (Presbytis entellus, Colobinae) was studied in Kanha Tiger Reserve, Central Indian Highlands between 1980 and 1983, followed by six brief return visits over ten years. Censuses of the 7 km² Kanha meadows demonstrated little change in population density and structure between 1982 and 1990; the population was consistently composed of one-male troops and all-male bands. During the return visits the focal C troop extended its known 74.5 ha range by only 5.6%. By 1993 two identified, habituated, adult females remained within the troop. The adult male was resident in C troop for ≥nine years and eight months.     

The social organization of forest hanuman langurs(Presbytis entellus)

The social organization of hanuman langurs (Presbytis entellus;Colobinae) was studied in Kanha Tiger Reserve, Central Indian Highlands, for 2300 hr (1980–1985), in a mosaic of moist deciduous forest and anthropogenic meadow. The langur population density was 46.15/km ² and the mean troop and band sizes were 21.7 and 14.0, respectively. Of 14 troops, 13 were one-male and 1 was trimale. The population adult sex ratio was 1:2.5. The majority of female sexual solicitations was directed toward the harem male. The birth season was December to May, with an estimated gestation of 171–224 days. A review of langur reproductive seasonality suggests that breeding throughout the year is confined to those populations able to exploit human food sources. Mortality during the first year of life was 40%, including infanticide. A significant positive correlation was found between the age of an infant at death or disappearance and the mother’s subsequent interbirth interval. Five cases of social change are described, including female transfer, one-male to multimale change, troop formation, and gradual and rapid replacement of troop males. Takeover-associated infant killing by band males, in an undisturbed moderate-density population, supported the sexual-selection/infanticide hypothesis but not the social-pathology hypothesis. However, it could not be directly confirmed that an invading infanticidal male gains a reproductive advantage. The male tenure of harems was estimated to be 45 months.     

The diet of the capped langur (Presbytis pileata) in a moist deciduous forest in Bangladesh

Capped langurs (Presbytis pileata) in Madhupur National Park in north-central Bangladesh have an annual diet that is comprised largely of mature leaves (42% of 20,460 total feeding records). Among colobine monkeys, only some populations of red colobus (Procolobus badius) have a diet richer in mature leaves. New leaves (11%) and fruit (24%) are the other annually important dietary items. Seasonal breakdown of this diet, however, revealed that during the monsoon months of May through September theP. pileata diet is approximately 50% fruit, including pulpy ripe fruit. This is also the period of maximum fruit availability. Data on diet and food availability indicate that while capped langurs subsist on mature leaves during the dry season (80% of diet from November to March), they select fruit and new leaves and switch to these foods whenever they are available. These data support the hypothesis that the colobine feeding strategy is adapted to cope with seasonal food scarcity.     

Feeding and ranging patterns of forest hanuman langurs (Presbytis entellus)

The feeding and ranging patterns of a troop of hanuman langurs (Presbytis entellus, Colobinae) were studied in Kanha Tiger Reserve, central Indian Highlands for 1850 hr (1981–1982), in a mosaic of moist deciduous forest and anthropogenic meadow. The location, size, and species of each tree within the 74.5-ha troop annual range was known and the phenology of all tree species was sampled. According to scan sampling, the troop spent 25.7% of the daytime feeding, with range use concentrated on an island of dry deciduous forest. Whereas adjacent troops occupied only the periphery of the focal troop's range, all-male bands occupied its center, especially during takeover and infanticidal attacks. The troop consumed items from 60 of the 67 species of trees and woody climbers available; mature leaves (34.9% of feeding time), fruits (24.4%), leaf buds (10.6%), flowers and flower buds (9.5%), young leaves (3.6%), insects (3.0%), and gum (1%). The monthly utilization of fruit, open leaf buds, and flower buds is correlated significantly with their abundance, and the troop spent significantly more time feeding and less time moving when consuming mature leaves. Comparison of tree dispersion and langur ranging patterns suggests that the distribution of the most important food trees is a major influence on their range use.     

Predation by the grey leaf monkey (Presbytis hosei) on the contents of a Bird's nest at Mt. Kinabalu Park,Sabah

An adult male grey leaf monkey (Presbytis hosei) was observed in Mt. Kinabalu Park, Sabah, Malaysia, raiding the nest of a grey-throated babbler (Stachyris nigriceps). The monkey removed from the nest and ate at least two eggs and perhaps one young hatchling. This incident appears to be the first reported case of anyPresbytis spp. consuming animal prey.     

Group fission in Nilgiri langurs (Presbytis johnii)

During a field study on habituated groups of wild Nilgiri langurs (Presbytis johnii),four cases of group fission were observed which differed markedly from group changes reported in other species of the same genus. All fissions occurred in groups with more than one mature male and roughly coincided with the onset of loud call vocalization by the second mature male group member. As a result of the fission the founder group factions acquired the structure of a onemale group. The filial factions consisted of both mature males and females and occupied, at least temporarily, a part of, or an area adjacent to, the founder group. During fission, the amount of aggressive interactions between the two mature males increased. However, the majority of agonistic interactions involved ritualized threat and intimidation behavior without physical aggression. In at least three cases the two mature males involved in the fission had not joined recently but had lived in these groups for three years or more. Although the presence of all male bands and single males in the two study populations indicate that male replacement by invasive takeovers may occur, it is suggested that in Nilgiri langurs, noninvasive fissions are probably another common mechanism for the foundation and maintenance of bisexual one-male groups.     

Father-son recognition in hanuman langurs (Presbytis entellus): A field experiment in India

A juvenile male langur, about 15 months old, was removed from his natal one-male-multi-female troop and reintroduced after 3.3 weeks. In attempts to protect the juvenile, his presumed father, the troop's resident male, charged the primatologist who removed and released the individual. After the second removal, the juvenile was introduced into a neighboring male band. The resident male attacked the band members to keep them away from his females. However, after 3.4 weeks of separation, the father and the son recognized each other, because the resident male showed no aggression towards his son and the latter did not run away from him. Kin-recognition is considered to be a mechanism in structuring coalitions within langur male bands.     

Seed dispersal by red howling monkeys (Alouatta seniculus) in the tropical rain forest of French Guiana

A 2-year field study of the frugivorous diet of a howling monkey troop, in a tropical rain forest in French Guiana, shows that they disperse by endozoochory ≥95% of plant species from which they eat ripe fruit. Passage through the digestive tract of howlers does not significantly modify the germination success of most plant species samples. Their low digestion rate (X = 20 hr 40 min) is the ultimate cause of a bimodal defecation rhythm that results in the concentration of 60% of defecations being deposited under sleeping sites. The distance of seed dispersal can reach more than 550 m from parent trees,with a mean of 260 m. Although howling monkeys consume fruits differing in morphological characteristics, they are particularly able to disseminate seeds of species whose fruits have a hard and indehiscent external coat or large seeds or both. In French Guiana, they may be especially important dispersers of the Sapotaceae with fruits that simultaneously present both characteristics.     

Patterns of grandmaternal behaviour in free-ranging Hanuman langurs (Presbytis entellus)

The behaviour of two Hanuman langur grandmothers towards their grandchildren is examined with emphasis on the spatial relationship, the contact behaviour, and vigilance. Interaction patterns with infants and juveniles are analysed separately to disclose the influence of a social partner's reproductive value and the variance of this value on grandmaternal behaviour. The shape of grandmaternal behaviour seems to differ for male and female grandchildren, and it seems to depend on the reproductive value of both, the grandmother and the grandchild. These results are in accordance with sociobiological hypotheses. Evaluation of costs and benefits suggests that grandmaternal behaviour in langurs can be called investment.     

Differentiation patterns in the E. MediterraneanScutellaria rubicunda group (Lamiaceae)

Strict sterility barriers where found between theScutellaria populations on Sicily and the Greek populations. The material from Samos is separated by a strict sterility barrier from the other Greek populations. In contrast, the populations on mainland Greece and adjacent islands are all ± interfertile. Three species are recognized,S. rubicunda Hornem., endemic to Sicily, andS. brevibracteata subsp.icarica, endemic to Samos and Ikaria. All other populations are referred toS. rupestris with eight subspecies, most of which are endemic to one island or to one mountain. Three new subspecies are described, viz. subsp.rechingeri and subsp.olympica, endemic to mt Vourinos and mt Olympus in North Greece, respectively, and subsp.caroli-henrici, native to the Malea peninsula of Peloponnisos. The phytogeographical connections and genetic differentiation within and between populations are discussed.Dedicated to Prof. DrK. H. Rechinger on the occasion of his 80th birthday.     

Intermale relations and troop male membership changes in langurs (Presbytis entellus) in Nepal

Data on intermale social relations and troop membership changes in one Nepalese high-altitude population of free-ranging langurs (Presbytis entellus)are reported here. Data were collected from six troops by three observers and cover 32 months of observations. The predominantly multi-male troops indicate an alternating pattern of exclusions and introductions with gradual adult male replacement. Takeovers and infant killing were not observed. Analysis of adult social behavior records show qualitative and quantitative differences in intrasexual relations, with primarily agonistic social contacts occurring between males. Agonistic encounters between females and between males differ in frequency of occurrence, types of be-haviors used, cause, and consistency in direction of threats between individuals. Individual adult male frequency of interaction with females and immatures varied significantly, with the majority of these interactions occurring between the dominant troop male and other troop members. Data indicate that intermale dominance is a major factor in determining male access to fertile females: This appears to be achieved by either directly excluding males from the troop or effectively “controlling” their inter-actions with troop females. Data from these studies are compared with data from other Presbytis entellusinvestigations. Review of these data suggests that intraspecific variability in intermale social dynamics and type of troop male membership change are correlated with the percentage of nontroop males. It is suggested that environmental pressures resulting in social crowding can be critical in determing the occurrence of takeovers in some populations of Presbytis entellus.     

Weaving a tight social net: Allogrooming in free-ranging female langurs (Presbytis entellus)

We studied grooming among adults of a one-male multifemale troop of free-ranging Hanuman langurs (Presbytis entellus)living near Jodhpur, India, for 9 years. The 11–13 females devoted about 6% of their day to allogrooming. Adult males, whose tenures averaged 2.2 years, were transient figures in the troop's history, as reflected by their rather peripheral role in the grooming network. Females groomed males 4–40 times more frequently (1006 episodes) than vice versa- (176 episodes). Adult females received 97% of all grooming from other adult females (6655 episodes). Although females exhibited an age- inversed dominance hierarchy, they did not compete for grooming access to particular troop mates. Dyads of all possible rank differences occurred as frequently as expected: 51% of grooming was directed up the hierarchy and 49% down it. Young, high- ranking individuals gave and received significantly more grooming than the oldest, low- ranking females did. The pattern seemed to be influenced by kin selection because of the presumably high degree of female relatedness. They invested most in troopmates with the highest reproductive value, i.e., the youngest individuals. This trend was coupled with a preference of closest kin (mothers and daughters). Reciprocity was the outstanding feature since all adult females groomed and were groomed by all others. Such a tight social net might establish the necessary cohesion during frequent territorial disputes with neighboring troops.     

Grooming site preferences in female langurs (Presbytis entellus)

Factors influencing grooming site preferences in adult female Hanuman langurs (Presbytis entellus) were investigated. The females belonged to a free-ranging harem troop (Jodhpur, India) and were observed for 569 hr by focal-female sampling. Decisive factors for grooming site preferences were the following: autogrooming was determined mostly by site accessiblity. Allogrooming was significantly concentrated on parts that are inaccessible to the groomee. Close female kin groomed significantly longer, more frequently, and more precisely at inaccessible body parts. Lower-ranking females were groomed significantly less often and more briefly but also more precisely at inaccessible parts. However, the latter might be due to a lower-ranking subjects desire to face away from the higher-ranking groomer in order to avoid eye contact. The data suggest that the groomee determines the sites being groomed.     

Factors influencing the population density of the hanuman langur (Presbytis entellus) in Sariska Tiger Reserve

We carried out a study of Hanuman langurs in Sariska Tiger Reserve, Rajasthan, India during three months in 1990. The area surveyed included habitat disturbed by human activity, with both the grazing of livestock and firewood collecting resulting in degraded forest. Langur population density was estimated to be between 19 and 36 animals/km². The density of langurs in disturbed areas was significantly lower than in undisturbed areas. Both tree cover, total tree, and shrub cover were positively correlated with langur density, suggesting that a lack of trees in disturbed areas may have caused the lower langur densities. Although bisexual groups were significantly more common in undisturbed areas the distribution of all male groups did not appear to be affected by human disturbance, suggesting that male bands are likely to inhabit more disturbed habitats than bisexual groups. We suggest that either a lack of food trees or the high density of predators in Sariska may prevent bisexual groups from inhabiting areas where tree cover is low, although the more mobile male groups can survive in these areas. Although Hanuman langurs are a relatively common species in India, these results suggest that they are not, as is commonly assumed, immune to the effects of human disturbance. In areas where langurs appear to survive in disturbed habitats the different response of bisexual and all male groups to disturbance may still result in serious disruption to the population structure.     

Social interactions among adult male langurs (Presbytis entellus) at Rajaji Wildlife Sanctuary

A population of langurs (Presbytis entellus)at the Rajaji Wildlife Sanctuary in northern India was investigated for 1820 hr throughout a 10-month period in 1978. Data were collected from four bisexual troops and the adult males that ranged outside of bisexual troops. Most (60%) of the observation hours occurred with a main study troop from which social and ecological data were collected. The langur population at Rajaji shows pronounced birth and mating seasons. The population density is high (ca. 80/km ²), with about 75% of the adult males living outside of bisexual troops, which typically are large and multimale. Males outside of bisexual troops occur in small all-male bands or as isolates. Relations between bisexual troops and all-male bands are characterized by relatively low levels of aggression, and members of all-male bands are able to associate with bisexual troops for prolonged periods during the mating season. As a result of these associations, nontroop males are about as successful as troop males in achieving reproductive access to troop females. These associations between bisexual troops and all-male bands occurred with a minimal amount of agonistic behavior and without mortality or injury to troop females or immatures.