Presbytis Entellus Research Articles

Foetal arm prolapse and presumed maternal death in a wild hanuman langur (Presbytis entellus)

During fieldwork in Kanha Tiger Reserve, Central India, in 1980 an adult female hanuman langur (Presbytis entellus) was observed with the forearm of a dead foetus protruding from her vagina without evidence of uterine contractions. It is likely that a transverse lie or oblique malpresentation with consequent foetal arm prolapse occurred during labour with subsequent impaction, uterine inertia, and foetal death. The female disappeared from the troop over the following 18 hr, presumably dying as a consequence of the complications of the malpresentation.

Male reproductive success in harem troops of hanuman langurs (Presbytis entellus)

Based on cross-sectional and longitudinal data collected in 1967–1988 by various observers, male reproductive success was studied in the Hanuman langurs of Jodhpur, India. The harem-structured social organization ensures a high degree of paternity certainty. Births occur throughout the year, with significant peaks and minima in March and November, respectively (n =398).The interbirth interval averages 16.7 months (n = 114).The duration of harem residencies varies between 3 days and ≥ 74.0 months, with a mean of 26.5 (n = 64). Harem holder replacements occur during all months of the year. No male achieves residency in more than one troop, suggesting that residency is associated with a distinct peak in the resource holding potential of a given male. Reproductive success among males varies considerably. Male mortality is high due to migration and intrasexual competition, leading to an adult sex ratio of 1:4.9. It is estimated that one-quarter of all adult males will never gain harem residency. Conceptions achieved outside harem residencies are so rare (4.7%) that a viable low-risk strategy, opting for longevity instead of harem residency, is unlikely. Tenure length has a stronger influence on male reproductive success than harem size because interbirth intervals are significantly shorter in small harems than in larger ones. It is assumed that females in one-male breeding structures compete for sperm and that such competition is more intense in larger harems.

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.

Associations between Langur Monkeys (Presbytis entellus) and Chital Deer (Axis axis): Chance Encounters or a Mutualism?

AbstractThe relationship between a troop of hanuman langur monkeys (Presbytis entellus) and chital deer (Axis axis) was examined in Kanha Tiger Reserve, Central Indian Highlands. The frequency distribution of closest approaches between the two species suggested that associations (defined as proximity < 25 m) were not chance encounters; 70.1% of all those herds observed within 200 m came within 25 m of the troop. Associations were more frequent and lasted longer during the hot and cold weather than in the monsoon. Chital initiated and terminated the majority of associations, whilst langurs terminated them more frequently than they initiated.The langur troop dropped a mean of 4.0 kg vegetation fresh weight/day and chital were seen to scavenge or glean this forage in 38.2% of associations; more frequently in the hot and cold weather than in the monsoon. Chital gleaned items from 19 species of tree, with Shorea robusta the most frequently utilized.Responses to potential predators suggested that chital and langur responded to each other's alarm behaviour. Chital alerted to langur alarm more frequently than vice versa. Antagonistic interactions between the two species were observed in 5.8% of associations, predominantly directed from langurs to chital.The study suggests that chital‐langur associations are asymmetrical mutualisms. Chital gained by opportunistically taking advantage of vegetation dropped by langurs, and by responding to langur alarm behaviour. The benefit, if any, to langurs was probably slight; they may have gained from responding to chital alarms but incurred costs of antagonism and feeding competition with chital.

Sexual Harassment in Langur Monkeys (Presbytis entellus): Competition for Ova, Sperm, and Nurture?

AbstractInterference of nonmating individuals in copulations was studied for 14 months in a harem troop of free‐ranging Hanuman langurs living in Rajasthan/India. 80.6% of 346 sexual interactions were harassed by members of all age‐sex classes except infant‐I. A mean of 1.6 (range 1–7) harassers cooperated entailing a mean of 1.9 (range 1–7) successive copulatory attempts of the disturbed couples. Rank did not influence the direction of male‐male harassment. However, higher‐ranking adult females harassed lower‐ranking twice as often (67.2%) as vice versa (32.8%). Moreover, only 58.8% of copulations of the 3 top‐ranking females were disturbed against 96.4% in the 3 lowest‐ranking.Harassment by adult males seems to reflect intrasexual competition for insemination of females. Harassing females possibly try to limit births and reduce future resource competition. Since insemination of one female may reduce the probability of another female's impregnation, harassment might also express sperm competition. The latter hypothesis is supported by the fact that 75.0% of all copulatory attempts of pregnant females were likewise disturbed. Since interference in nonfertile matings cannot reflect resource competition, it is assumed that copulating pregnant females try to deplete the sperm available to competing fertile females. Immatures harassing maternal copulations obviously try to delay the births of siblings who are rivals for nurture.

Fate of ousted male residents of one-male bisexual troops of Hanuman langurs (Presbytis entellus) at Jodhpur, Rajasthan, India

Little is known about the fate of adult male residents after they are ousted from bisexual one-male troops of Hanuman langurs (Presbytis entellus) in the course of adult male replacements. In a long term study at Jodhpur, Rajasthan, it was possible to reconstruct partial life histories of several ousted residents. One resident was killed during the male change. Ousted residents did not regain residency despite their continued invasions into bisexual troops. It is assumed that the males' chances to take over and to defend a troop are restricted to an age of 9–14 years, when the males are in prime physical condition. One male became solitary for some months while trying to regain residency of his old troop, before joining some “alien” males. As a rule, males are likely to rejoin their own male bands if they are ousted after short periods of residency. If the residency exceeds 3 months then the ongoing structural change in the former band may prevent their reintegration. However, in such cases, ousted residents which belonged to the same band may reunite and mingle with another male band which lacks prime males. Weaned sons may follow their fathers after ousting. In the case of numerous weaned offspring, fathers and sons may together form at least temporary new male bands.

Male competition and coalitions in langurs (Presbytis entellus) at Jodhpur, Rajasthan, India

During a 15 month study on free ranging langurs (Presbytis entellus) at Jodhpur, Rajasthan, India, 5 adult male replacements were observed as a result of nontroop male invasions into the home ranges of 3 neighbouring one-male troops comprising 16–28 members each. Jodhpur langurs have no breeding season. Periods of instability during resident male changes lasted 11–119 days. Linear dominance hierarchies could be detected within the 3 main rival male bands of 2, 5, and 28–35 members. The respective alphas drove their allies away after their bands succeeded cooperatively at occupying a troop. During gradual replacements interim residencies alternated with multi-male stages. A large band's alpha may have had better chances to win the competition, since adult and nonadult allies functioned as “buffers” in agonistic encounters. The role of kin selection in structuring the composition of male bands and male coalitional behaviour cannot yet be quantified. Tactical “deceit” of powerful males to cause unrealistic expectations and in this way agonistic engagement of less strong males can be ruled out. “Sneaking copulations” is a proximate advantage for subordinate supporters, since they participated in 61.9% of all sexual interactions. Female promiscuity might reflect a strategy to induce male-male competition and thus select for a strong resident.

Sociobiology of Hanuman langurs (Presbytis entellus): introduction into the Jodhpur field project

The conceptual development of a longterm project on Hanuman langurs (Presbytis entellus) is described. The joint indo-german project was performed at Jodhpur, India, starting in 1977. Its main aim was to study the interrelations between individual life histories and troop histories. A general overview of the habitat and the langur population is presented.

Troop history, female reproductive strategies and timing of male change in Hanuman langurs,Presbytis entellus

Female reproductive data are presented from 9 years of longitudinal observations on two troops of Hanuman langurs (Presbytis entellus) living around Jodhpur, India. On the basis of 89 live births interbirth intervals were calculated to examine the effect of demographic factors on reproductive behaviour and troop composition. Sex of an infant seems to influence the length of intervals which are longer after the birth of female infants at an average of 1.7 months. It is suggested that this may be an outcome of differential maternal investment by allocating more time and energy towards female infants who run a higher mortality risk than male infants, at least up to an age of 27 months. Troopspecific interbirth intervals are influenced by social events. If the last infant is still alive when the next one is conceived, the intervals are significantly longer than after the premature loss of an infant (Bijolai troop: 15.6 vs. 12.1 months; Kailana-1 troop: 16.7 vs. 11.4 months). During undisturbed male tenureship intervals are shorter than after a male change (Bijolai troop: 14.3 vs. 16.0 months; Kailana-I troop: 15.6 vs. 17.5 months). Thus the frequency of male changes can influence the demography of a troop. Furthermore, the data suggest that take-overs are optimally timed by males. New males tend to take over a troop when most of the females are cycling.

Infanticide and juvenilicide in Hanuman langurs (Presbytis entellus) around Jodhpur, India

Ten cases of infant killings and 2 cases of juvenile killings were observed in two troops of Hanuman langurs, (Presbytis entellus) around Jodhpur, India. Fatal attacks on infants and juveniles are classified into four categories. The process of infanticide was observed from start to end and is described in detail for 3 cases. The age of the victims ranged from 0.2 to 48 months. The interbirth interval among females whose infants were killed is significantly shorter compared to females whose infants survived. In ourt study, 7 cases support the reproductive advantage hypothesis, that infanticide is an adaptive behaviour to increase male reproductive success. The remaining 5 cases do not fit into the reproductive advantage hypothesis. In these cases, victims are over 8 months old, and as such their deaths could not shorten the interbirth interval. It appears that by killing older infants and juveniles the males obtain an advantage in resource competition for their offspring. An alternative is that new males chase or peripheralise the older infants and juveniles, which leads to 97% predominant uni-male troop structure in Jodhpur.

Abortions in free ranging Hanuman langurs (Presbytis entellus) — a male induced strategy?

During a 10-year long term study, 6 eye-witnessed and 1 pressumed cases of abortions occurred in 3 one-male bisexual troops of free ranging langurs (Presbytis entellus) near Jodhpur, Rajasthan, India. The age of the unborns varied from 35 to about 200 days. The subsequent birth interval ranged between 7.1–21.1 months. 2 miscarriages occurred during stable periods of residency of a single male. 5 cases occurred prior to or after infanticide in connection with male changes. In one case a female was attacked by the new male before she aborted. In one case a female presumably aborted after attacks on her semiweaned infant. Most of the reproductive losses hence seem to be related to psychical and physical stress exerted by new males on pregnant females. As part of their reproductive strategy, males reduce their waiting time to insemination in this way. Abortions may likewise represent an adaptive reproductive strategy of females, who prefer to abort instead of investing in a foetus which is likely to be killed after birth.

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.

Reproductive exocrine and endocrine profile of female langur monkeys, Presbytis entellus.

In 5 caged langurs menstrual cycle length (for 125 cycles) varied from 18 to 45 days with a mean +/- s.d. of 26.3 +/- 3.6 days. Menstruation lasted for 2 days. A distinct cycle of vaginal smear cells was observed with a maximum cornification on Day 10 coinciding with the serum oestradiol peak. A monophasic pattern of vaginal temperature with a significant nadir on Day 11, 1 day after the oestradiol peak, was observed. Serum sialic acid concentrations directly reflected the oestrogenic activity and showed a significant peak on Day 10, coinciding with the oestradiol peak and was followed by a progesterone rise. Langurs menstruated throughout the year without showing any sign of summer amenorrhoea. We suggest that maximum cornification, vaginal temperature nadir and serum sialic acid peak could be used as markers for prediction and detection of the time of ovulation in langur monkeys.

Female Primate Sexual Behavior and Conception: Are There Really Sperm to Spare? [and Comments and Reply

Female Primate Sexual Behavior and Conception: Are There Really Sperm to Spare? [and Comments and Reply

The variable social organization of hanuman langurs(Presbytis entellus), infanticide, and the monopolization of females

Data from 24 wild populations of hanuman langurs (Presbytis entellus)in south Asia are used to test hypotheses seeking to explain variation in troop structure and the incidence of infanticide. The occurrence of infanticide is associated with a one-male troop structure and not with a high density. The density, predation, and economic-advantage hypotheses, as explanations for the occurrence of one-male and multimale troops, are not supported by the review. However, the monopolization hypothesis is not contradicted; the number of adult males per troop is significantly correlated with troop size and with the number of adult females per troop. Therefore it is suggested that a one-male troop structure will arise if a male is able to monopolize a group of females, a multimale troop if he cannot. One-male troops may predispose to infanticide because of high variance in male mating success and high intermale competition between groups rather than within troops. If female dispersion determines troop structure, it is speculated that females could manipulate males to form a multimale society if the advantages in terms of infant survival and intertroop conflict exceeded the costs in terms of not producing infanticidal “sexy sons.”

Patterns of reproduction and mortality in two captive colonies of hanuman langur monkeys (Presbytis entellus).

Longitudinal reproductive and mortality data collected from two colonies of Hanuman langur monkeys (Presbytis entellus) in California (University of California, Berkeley; San Diego Zoo) are presented. Approximately 10 years of data from each facility reveal that langur monkey females reach reproductive maturity between 3 and 5 years and have median birth intervals, following the birth of a live infant that survives beyond 9 months, of approximately 15.5 months. Births are not seasonal at either facility and pregnancy failure rates at UCB are approximately 30%. Mortality of subadults was highest during the neonatal period (<30 days), and probability of Sarvivorship at 5 years is between .41 and .50. Observed differences and similarities in patterns of reproduction and mortality between the two colonies and field populations are discussed.

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/km2 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.

Infanticide among free-ranging langurs (Presbytis entellus) at jodhpur (Rajasthan/India): Recent observations and a reconsideration of hypotheses

Considerable disagreement characterizes the debate concerning frequency, causation, and function of infanticide in connection with adult male replacements in bisexual one-male troops of hanuman langurs (Presbytis entellus). Detailed observations are presented about two noninfanticidal and three infanticidal male changes including six eye-witness and five presumed cases of infanticide within three langur troops during a long-term study at Jodhpur, Rajasthan, India. The results do not support any explanatory hypotheses focussing on social crowding, regulation of population density, social stress, sexual frustration, incest avoidance, or social bonding, but are in general though not total agreement with the reproductive advantage hypothesis: mainly unrelated infants were killed (one possible exception), the infanticidal male generally sired the subsequent offspring (one exception), and the mean interbirth interval subsequent to infanticide is by 2.1 months shortened. Likewise, several cases of stress induced abortions occurred. It is demonstrated that postconception estrous behaviour is by no means a female counterstrategy to infanticide in order to confuse males concerning the issue of paternity, since an infanticidal male did not spare the subsequent offspring of mothers who copulated with him during pregnancy and pregnant females did not discriminate between fathers and non-fathers.

Upperlimb skeletal elements of miocene cercopithecoids from east Africa: Implications for function and taxonomy

Old collections and unpublished newly-discovered specimens of Miocene cercopithecoids studied here include humeri and proximal ulnae from Maboko (KNM MB 2, KNM MB 3, KNM MB 19, KNM MB 32, KNM MB 12038, KNM MB 12044), Nyakach (KNM NC 9824) in Kenya and from Napak (NAP V-8.85) in Uganda. This work leads to the conclusion that two different groups of monkeys may have co-existed in East Africa in the Middle Miocene. After comparison with extant cercopithecoids (Colobus polykomos, Colobus badius, Colubus angolensis, Colobus guereza, Cercopithecus aethiops, Cercopithecus ascanius, Nasalis larvatus, Presbytis entellus and severalPapio andMacaca), the fossils can be divided into two morphological groups. In the distal humerus, the shape of thetrochlea humeri and the orientation of theepicondylus medialis are distinctive; in the ulnae, the distinction is mainly based on the morphology of theincisura trochlearis. Thus, we would have a more terrestrial group and a more arboreal one. The differences (not linked with sex) are large enough to indicate a taxonomic difference (as proposed on the teeth collected to the same sites, by several authors). At this stage, we cannot assign with certainty the specimens to one taxon or the other (Victoriapithecus macinnesi orVictoriapithecus leakeyi).

Infanticide in an undisturbed forest population of hanuman langurs, Presbytis entellus

Observations of infanticide in a troop of undisturbed, forest hanuman langurs by members of an invading all-male band are reported. The data, whilst consistent with the sexual selection hypothesis, did not support the social pathology hypothesis. Data from different langur populations supported the prediction, derived from the sexual selection hypothesis, that troop take-overs should occur between the birth and mating seasons. The occurrence of take-overs in different langur populations was associated with a predominantly one-male troop structure and not with high density.