Differential detectability of primates between primary and selectively logged habitats and implications for population surveys

Much information has been published concerning the accurary of various techniques commonly used for censusing primates. The sources of bias may vary according to the technique used. Accuracy may depend on population density as well as on differential visibility and hence detectability between areas. This paper provides evidence that primates may alter their behavior between areas of primary and selectively logged habitat, which in turn could affect census results. Adoption of cryptic behavior, changes in behavioral profile, and reduction in calling rates reduce the detectability of certain species. Increases in the frequency of subgrouping or in group dispersion may introduce a danger of overestimation of other species, unless differences in the size of foraging units are taken into account.     

Life-Phase Related Changes in Male Loud Call Characteristics and Testosterone Levels in Wild Thomas Langurs

Males in many primate species give loud calls. Lifetime changes in loud calls may be due to either age or social changes. We examined loud call characteristics, loud call production and levels of fecal testosterone among 4 life-phases of male Thomas langurs (Presbytis thomasi): all-male band (AMB), early, middle, and late life-phase in mixed-sex groups. Discriminant analyses showed that a high percentage of loud calls could be assigned correctly to the proper life-phase. The most significant change in loud call characteristics is an increase in tonal units and duration from the AMB to the early life-phase, accompanied by a decrease in non-tonal units. Since adult AMB males have a similar age to that of early life-phase males, we suggest that social rather than age-related changes underlie the loud call differences between AMB males and early life-phase males. This could also be related to the increase in testosterone levels from the AMB to the early life-phase. In addition, we postulate that females may use loud call characteristics as a cue to choose between young and old males once they decided to leave their current male, and possibly also as a cue to decide to leave their current male as he enters his late life-phase.     

Female dispersal,social organization,and infanticide in langurs: Are they linked to human disturbance?

Female dispersal in gregarious animals can involve the desertion of a site, desertion of a social group, or both. Group desertion may be related to inbreeding avoidance. Group fidelity may result from cooperation among females in a group. Site fidelity will be more likely when food can be monopolized and when the population density is close to habitat saturation. The degree of habitat saturation was approximated with a measure of human disturbance. The influence of these various factors on the incidence of female dispersal was investigated for langur populations using data from the literature. The results suggest that female dispersal in langurs involved site desertion, not group desertion. The incidence of female dispersal may affect the social organization of langurs. I propose that when females do not disperse, male takeovers prevail, whereas in populations where female dispersal regularly occurs bisexual groups are disbanded or new groups are formed, a process I call female split-merger. Male takeover is thought to occur when site fidelity is high, female split-merger when site fidelity is low. These processes were indeed found to occur in these circumstances. The dispersal of females might prevent infanticide, whereas male takeover might promote it. Indeed, in studies with male takeover, more infants fell victim to infanticide than in studies with female split-merger. Therefore, female dispersal in langurs is an effective female counterstrategy to infanticide. The factor that had the most profound effect on female dispersal, social organization, and infanticide was habitat saturation. Habitat saturation was measured as the degree of human disturbance, and its influence on the behavior of langurs is probably of relatively recent date. This may lead to an evolutionary transient situation and may explain the discrepancy between current socioecological theories and the behavior of langurs in populations lacking female dispersal. Am. J. Primatol. 44:235–254, 1998. © 1998 Wiley-Liss, Inc.     

白头叶猴（Presbytis leucocephalus）活动时间分配

通过白头叶猴活动时间分配的研究,探讨引起种群活动时间分配的内在和环境因素。这些因素通过群体及各性别年龄组能量的不同需求改变其活动时间分配。分析结果表明,动物活动时间分配反映各种因素对群体的综合作用。作者推测,在白头叶猴分布区的南北种群间,因地理位置及植被保护状况的差异可能有不同的活动时间分配。在所观察的几个行为因子中,运动和休息相关性最大。群体本身的结构也造成群内各性别年龄组间活动时间分配的差异。     

广西白头叶猴栖息地特征

白头叶猴是我国独有的灵长类物种,其栖息地十分狭小而分散。典型的热带喀斯特峰丛洼地-峰丛谷地地貌组合,特殊的石灰岩季雨林或次生植被和多种石灰土构成的石山景观,与周边的土山景观有明显区别。环境的异质性和不连续性,使之成为边界明显但又互相隔离的同质性斑块,为穴居和过群居生活的白头叶猴提供了至关重要的生存空间。白头叶猴这一适应于热带气候,善攀爬、植食性和穴居习性的物种,选择低峰丛洼地-峰丛谷地作为适宜的栖息地,是在长期进化过程中生态适应的结果。目前,白头叶猴仅分布于几处互相隔离的地块。近几十年来,由于人类活动的强烈干扰,使其栖息地急速缩小和更加分散。只有正确处理人地关系、人与野生动物的关系,禁止石山地区的过度开发,维持这一自然综合体的完整性和保持景观异质性,白头叶猴才有生存的可能和发展的机会。     

Assessment of female reproductive status in captive-housed Hanuman langurs (Presbytis entellus) by measurement of urinary and fecal steroid excretion patterns

The study reports on the use of urinary and fecal hormone measurements for monitoring female reproductive status in captive-housed Hanuman langurs (Presbytis entellus). Matched urine and fecal samples collected throughout 7 complete menstrual cycles of two females, and during part of one pregnancy in a third female were analyzed. Estrone conjugates (E1C) and immunoreactive pregnanediol glucuronide (PdG) in urine and immunoreactive estradiol (E2), progesterone (P4), pregnanediol (Pd) and 20α-hydroxyprogesterone (20αOHP) in feces were measured by enzymeimmunoassay. E1C and PdG in urine were excreted in a cyclic pattern with E1C levels increasing 3- to 4-fold during the follicular phase to reach preovulatory peak values 2 days before a defined rise in PdG concentrations. Cycle lengths ranged between 20 and 34 days comprising a variable follicular phase of 7–21 days and a more consistent luteal phase of 12–14 days. High pressure liquid chromatography (HPLC) analysis of fecal extracts confirmed the presence of all fecal hormones measured, but indicated large amounts of additional immunoreactivity in the three progestin assays. The patterns of excretion of fecal E2 and all three fecal progestins corresponded well with those of steroid metabolites in urine in showing a clear and well defined follicular phase E2 rise followed by a luteal phase progestin increase. Measurement of 20αOHP immunoreactivity revealed the most stable baseline and the highest follicular/luteal phase differential. Levels of all hormones were clearly elevated during pregnancy although urinary E1C and PdG showed a more pronounced increase compared to fecal metabolites. The results indicate that urinary and fecal hormone analysis can be applied to noninvasive monitoring of reproductive status in the Hanuman langur. © 1995 Wiley-Liss, Inc.     

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.     

What Hanuman langur males know about female reproductive status

In species with a high risk of infanticide, a conflict of interest exists between the sexes over the amount of paternity information that is available to males. While females are expected to keep males unaware of their reproductive status in order to confuse paternity, selection should favor those male traits that enhance the males' assessment of female status and consequently of paternity probability. In Hanuman langurs (Semnopithecus entellus), a species that is extremely vulnerable to infanticide, females have been shown to successfully conceal the exact timing of ovulation from males--perhaps because they exhibit no sexual swelling and mate during all reproductive phases, including gestation. Nevertheless, it remains unclear whether males have hitherto unrecognized information about females' reproductive condition on a broader level that could still enhance male reproductive success. We investigated male assessment of female reproductive states in a population of wild Hanuman langurs as indicated by changes in male behavior, such as rates of copulations, anogenital inspections, and consortships, in relation to different female receptive periods (pregnant, fertile-nonconceptional, and conceptional). Our data indicate that males were able to discern qualitatively distinct reproductive states. Males were more interested in fertile than pregnant females, as indicated by higher copulation rates. Based on consortships, males distinguished fertile from nonfertile phases, as well as fertile, nonconceptional receptive periods from conceptional ones. Hanuman langur males are thus not as unaware of female reproductive condition as previously thought, supporting the idea of an ongoing battle of the sexes over paternity information. However, granting some knowledge while at the same time concealing the exact day of ovulation may also reflect a pure female strategy of balancing paternity concentration with paternity confusion, which is the most likely strategy in this system with high infanticide risk and male defense of infants.     

The importance of ingestion rates for estimating food quality and energy intake

Testing ecological or socioecological models in primatology often requires estimates of individual energy intake. It is a well established fact that the nutrient content (and hence the energy content) of primate food items is highly variable. The second variable in determining primate energy intake, i.e., the ingestion rate, has often been ignored, and few studies have attempted to estimate the relative importance of the two predictors. In the present study individual ingestion rates were measured in two ecologically very different populations of Hanuman langurs (Semnopithecus entellus) at Jodhpur, India, and Ramnagar, Nepal. Protein and soluble sugar concentrations in 50 and 100 food items. respectively, were measured using standardized methods. Variation in ingestion rates (gram of dry matter per minute) was markedly greater among food items than among langur individuals in both populations, but did not differ systematically among food item categories defined according to plant part and age. General linear models (GLMs) with ingestion rate, protein, and soluble sugar content explained 40-80% of the variation in energy intake rates (kJ/min). The relative importance of ingestion rates was either similar (Ramnagar) or much greater (Jodhpur) than the role of sugar and/or protein content in determining the energy intake rates of different items. These results may impact socioecological studies of variation in individual energy budgets, investigations of food choice in relation to chemical composition or sensory characteristics, and research into habitat preferences that measures habitat quality in terms of abundance of important food sources. We suggest a definition of food quality that includes not only the amount of valuable food contents (energy, vitamins, and minerals) and the digestibility of different foods, but also the rate at which the food can be harvested and processed. Such an extended definition seems necessary because time may constrain primates when feeding competition is intense and foraging is risk-prone.     

Sex Differential Behavior of Immature Hanuman Langurs (Presbytis entellus) in Ramnagar, South Nepal

We investigated sex differences in the social behavior of immature Hanuman langurs (Presbytis entellus) in the light of sex-specifically different life-courses and Hanuman langur characteristics, such as the individualistic dominance hierarchy and the rarity of intragroup coalitions among adult females. We observed four immature female and four immature male langurs—all members of the same free-ranging multimale multifemale group in Ramnagar, South Nepal—from November 1992 to February 1993 for 288 hr via focal-animal and instantaneous sampling techniques. Immature females spent significantly more time in proximity to other group members than immature males did. They had more physical contact and groomed more. Other immature females were their preferred social partners. Immature males also preferred like-aged females. They restricted their relationships with other immature males to proximity and occasional grooming. Monitoring was directed especially toward adult males. Female behavior can be interpreted as oriented toward integration into the female social network and their age-inverted dominance hierarchy. Males seem to prepare for leaving their natal group and for future strong intrasexual competition.