Trachypithecus Leucocephalus Research Articles

Male attacks on infants and infant death during male takeovers in wild white‐headed langurs (Trachypithecus leucocephalus)

Infanticide was first observed in langurs nearly 50 years ago, and this rare phenomenon has been inferred to have either an evolutionarily adaptive function or to be a pathological and non-functional behavior. In this study, we report 5 male takeover events in one-male groups of white-headed langurs in the Nongguan Karst Hills, Guangxi, China from 1998 to 2006. We recorded 13 attacks on 9 infants by extra-group males or new resident males. During the male takeovers, all of the infants younger than 6 months (with an average age of 3.6 months [N = 11]) in the groups disappeared. The infant death rate during the 4.2 months after takeover by a new male was significantly higher than the infant death rate calculated for most of the year. Older infants that were still nursing (with an average age of 14.1 months [N = 7]) were often attacked and seriously wounded by the extra-group males or new resident males, but all of them survived. The interbirth intervals of females whose infants were assumed to be killed by males were significantly reduced relative to those of females in groups with stable male tenure (mean = 10 months vs 25 months). Our data suggest that males kill unrelated and unweaned infants during the takeover period to decrease the time until the infants' mothers resume fertility. Thus, infanticide would support sexual selection theory in white-headed langurs. The data also show that infanticidal behavior was directed toward the infants, especially those who were still nursing. Female dispersal may function as a counter-strategy to avoid infanticide.

Genetic analysis of group composition and relatedness in white‐headed langurs

We collected fecal samples of white-headed langurs from 3 of the 4 remaining habitat fragments (Fa, Fb and CZ) located in southwestern Guangxi, China in Nov 2005, and used 5 microsatellite loci and the SRY gene to assess the relatedness between 46 langurs within and between groups. We observed 2 forms of group structure: one-male/multi-female groups (OMGs) and all-male groups (AMGs). One AMG in Fa was composed of 2 generations, included a father, 2 sons and 1 unrelated male, and all OMGs in all 3 habitats included 1 resident male, several adult females and offspring. Of the 21 identified father-offspring cases, the resident male fathered 20 (95%) and the non-resident male sired 1 (5%), suggesting that adult males had overwhelming priority of access to females as the resident male in an OMG, while the non-resident male may also have the opportunity to adopt surreptitious mating strategies.

Food diversity and choice of white-headed langur in fragmented limestone hill habitat in Guangxi, China

We studied the diet and food choice of three groups of white-headed langurs (Trachypithecus leucocephalus) from July 2002 to June 2003 at Fusui Rare Animal Reserve, Guangxi, China. Data were collected from via focus group sampling, with continuous recording. A total of 109 plant species (including 19 unidentified species) were used as food by the white-headed langur. They spent 91.6% of total feeding time feeding on leaves, 4.2% on fruits and 3.3% on stems. Flowers and other food items accounted for only 0.3% and 0.6% of total feeding time, respectively. There were significant seasonal variations in the langurs’ diets with changes in the total number of species and the diversity of food species consumed. The langurs used significantly more plant species as food in the rainy season than in the dry season (36 species vs. 26.5 species). Dietary diversity was also significantly higher in the rainy season than in the dry season (2.6 vs. 2.4). No significant seasonal variation was found in the percentage of various plant parts in their monthly diets. Though the white-headed langur fed on many plant species, 11 species made up 84.9% of their diet. There were no significant correlations between the percentage of feeding time for main food plant species and their corresponding abundance in the habitat, content of water, crude protein, crude fiber and the ratio of crude protein to crude fiber. These results suggest that food choice of the white-headed langur is not influenced by their abundance and nutritional content.

Parturitions in Wild White-Headed Langurs (Trachypithecus leucocephalus) in the Nongguan Hills, China

There are few detailed descriptions of parturition behavior in wild primates. Here we report for the first time birth-related behaviors in a highly endangered colobine monkey endemic to southwest China, the white-headed langur (Trachypithecus leucocephalus). We video recorded three complete birth events in three parturient females living in one reproductive group. The births occurred during the night at one of the group’s sleeping sites. One parturient was primiparous, while the other two were multiparous. All three delivered close to other group members. Common behaviors among the parturients included adopting a raised-rump posture during contractions, manual inspection of the anogenital area followed by hand-licking, manual self-assistance as the infant emerged, holding and licking the infant immediately after the birth, and ingesting the placenta. However, we found considerable individual variation in birth-related behaviors. The primiparous female had the longest prepartum phase and more contractions than the two multiparous females. All three mothers ingested the placenta, but the primipare took much longer than the two multiparous mothers to deliver the placenta, start to ingest it, and consume it. Other group members had little interaction with the parturients during the prepartum phase, but showed intense interest in the neonates. The newly born infants were held by nonmaternal adult females of the group within 5–9 h of their birth. Our case studies stress the importance of the social context at parturition in group-living primates, and suggest that parity of parturients may influence birth-related behavior.

Sleeping site use of the white-headed langur Trachypithecus leucocephalus: The role of predation risk, territorial defense, and proximity to feeding sites

Abstract We collected data on sleeping site use from two groups of white-headed langurs Trachypithecus leucocephalus living in Fusui Nature Reserve, China between August 2007 and July 2008. This information was used to test several hypotheses regarding ultimate causes of sleeping site use in this primate. White-headed langurs slept either in caves (17 sites) or on a cliff ledge (one site). They used all sleeping sites repeatedly, and reused some of them on consecutive nights; three nights was the longest consecutive use of any one sleep site. We suggest that langurs use sleeping sites to make approach and attack by predators difficult, and to increase their own familiarity with a location so as to improve chances for escape. Langurs’ cryptic behaviors with an increased level of vigilance before entering sleeping sites may also help in decreasing the possibility of detection by predators. Group 1 spent more sleeping nights in the central area of their territory than expected; in contrast, group 2 spent more sleeping nights in the periphery of their territory, which overlaps with that of another groups, than expected. The position of sleeping site relative to the last feeding site of the day and the first feeding site of the subsequent morning indicated a strategy closer to that of a multiple central place forager than of a central place forager. These results suggest that territory defense and food access may play an important role in sleeping site use of white-headed langurs.

A Video-Aided Study of the Diet of Wild White-Headed Langurs (Trachypithecus leucocephalus)

Asian leaf-eating monkeys have flexible, environmentally adaptable feeding strategies. The diet and food choices of white-headed langurs (Trachypithecus leucocephalus) have, however, not yet been studied in the Nongguan Karst Hills in China, where one of the two main surviving populations of this endangered species lives. From 2000 to 2002 inclusive, we adopted an innovative video playback analysis method to identify the food species used by the langurs and to calculate the corresponding feeding frequency for each species. The video-aided methodology was shown to be efficient. It provided high-quality images, and the plant species could be identified in 98.3% of the feeding records. Based on this analysis, we found that the langurs in Nongguan fed on 70 species of plants, among which 24 were identified as their staple food species. The cumulative curve for the staple food species reached a plateau at 255 (43.7%) feeding records. This result indicated that most of the langurs’ staple food species had been identified by the analysis.

Male takeover, infanticide, and female countertactics in white-headed leaf monkeys (Trachypithecus leucocephalus)

Infanticide by males is common in mammalian species such as primates in which lactation lasts much longer than gestation. It frequently occurs in one-male groups following male takeovers and is likely a male reproductive strategy. Reported female countertactics include abrupt weaning of infants, dispersal, or paternity confusion. Here, we estimated costs of female countertactics in terms of weaning ages and interbirth intervals. We observed a population of white-headed leaf monkeys (Trachypithecus leucocephalus) in Nongguan Nature Reserve, China (1995–2006) mainly composed of one-male groups. Takeovers (N = 11) coincided with the peak conception period. Detailed data are presented for five takeovers (34 females, 29 infants, and 47 group-years) leading to six infant disappearances (42.9% of infant mortality). All presumed infanticides were in accordance with the sexual selection hypothesis. Following a takeover, females without infants or with old infants stayed with the new males, incurring no or low costs (via abrupt weaning). Females with young infants dispersing with the old males also experienced low costs. High costs (due to infant loss) were incurred by pregnant females and those with young infants who stayed with the new males indicating that paternity was not confused. Costs in terms of long interbirth intervals were also high for females leaving with the old males to later join the new males, despite infant survival. Female countertactics reflected female philopatry mediated by infant age. Presumably due to the seasonal timing of takeovers, most countertactics seemed successful given that 32.3% of females apparently incurred no costs and 41.2% incurred only low costs.

Factors Affecting the Ranging Behavior of White-headed Langurs (Trachypithecus leucocephalus)

Ranging behavior is an important aspect of animal behavior that researchers use to investigate ecological influences on individual behavior. We studied the influence of diet, water resources, and sleeping sites on the ranging behavior of 2 groups of white-headed langurs (Trachypithecus leucocephalus) in a limestone habitat at Fusui Nature Reserve, China, between August 2007 and July 2008. During the study period, the total home range sizes for the 2 focal groups were 23.8 ha and 33.8 ha, the mean daily path lengths were 491 m and 512 m, and leaves accounted for 83.4% and 91.0% of the diet, which are well within the range of variation reported for other Trachypithecus. One focal group traveled significantly longer distances in the rainy season months than in the dry season months. This variation may be related to the seasonal difference in food availability and diet. The langurs did not use their home ranges uniformly, and 50% of their activities occurred within 11% (group 1) and 20% (group 2) of their home ranges. The most heavily used quadrats in the home ranges were located near the most frequently used sleeping sites. Moreover, the core areas (>70% of location records) of both groups’ home ranges included ≥1 permanent water pool. The langurs ventured to these pools for drinking when surface water became scarce in the dry season. These results suggest that sleeping sites and water scarcity may be significant influences on the ranging behavior of white-headed langurs in limestone habitat.

Behavioral Observations and Notes on the Vertical Ranging Pattern of the Critically Endangered Cat Ba Langur (Trachypithecus Poliocephalus Poliocephalus) in Vietnam

The golden-headed or Cat Ba langur (Trachypithecus poliocephalus poliocephalus) is endemic to Cat Ba Island in northern Vietnam. Two free-ranging groups were studied for 22 days of data collection. Behavioral data were collected via instantaneous scan sampling for determining the time budget, activity pattern and vertical ranging pattern of these groups. The langurs spent two thirds of their time resting, 15% foraging, 11% moving and 8% in social activities. Time budgets differed between age classes, with infants and juveniles spending more time being social. The activity pattern of the groups revealed that the langurs rested mostly during the morning and at midday when most of the social behavior was also observed. Foraging and moving occurred more often in the morning and afternoon, with foraging being more pronounced later in the day. With respect to their ranging, the langurs spent most of their time in the higher elevations, but foraged more in the lower elevations of the hills where they live. In this study, we show that the best time to census this Critically Endangered species is from sunrise till 12:00 am.

Isolation and characterization of 10 microsatellite loci for White-headed Langur (Trachypithecus leucocephalus)

The polymorphic microsatellite loci were isolated and characterized from a microsatellite DNA-enriched DNA library for the white-headed langur (Trachypithecus leucocephalus), which is listed as one of the top 25 most endangered primate species in the world during the year of 2004–2006. These loci showed polymorphism information content ranging from 0.590 to 0.874, allele numbers ranging from 4 to 14, and observed and expected heterozygosities from 0.660 to 0.906 and 0.526 to 0.920 respectively. Thus, we expect that these markers will be useful for conservation genetic of white-headed langur.

Landscapes and Ecosystems of Tropical Limestone: Case Study of the Cat Ba Islands, Vietnam

The Cat Ba Islands in Hai Phong City, northern Vietnam, consist of a large limestone island with a maximum height of 322 m above sea level and 366 small limestone islets with a total area of about <TEX>$180\;km^2$</TEX>. The islands are relicts of karst limestone mountains that became submerged during the Holocene transgression 7000 - 8000 year ago. The combination of the longtime karst process and recent marine processes in the monsoonal tropical zone has created a very diversity landscape on the Cat Ba Islands that can be divided into 3 habitat types with 16 forms. The first habitat type is the karst mountains and hills, including karst mountains and hills, karst valleys and dolines, karst lakes, karst caves, and old marine terraces. The second habitat type is the limestone island coast, including beaches, mangrove marshes, tidal flats, rocky coasts, marine notch caves, marine karst lakes, and bights. The third habitat type is karst plains submerged by the sea, including karst cones (fengcong) and towers (fengling), bedrock exposed on the seabed, sandy mud seabed, and submerged channels. Like the landscape, the biodiversity is also high in ecosystems composed of scrub cover - bare hills, rainy tropical forests, paddy fields and gardens, swamps, caves, beaches, mangrove forests, tidal flats, rocky coasts, marine krast lakes, coral reefs, hard bottoms, seagrass beds and soft bottoms. The ecosystems on the Cat Ba Islands that support very high species biodiversity include tropical evergreen rainforests, soft bottoms; coral reefs, mangrove forests, and marine karst lakes. A total of 2,380 species have been recorded in the Cat Ba Islands, included 741 species of terrestrial plants; 282 species of terrestrial animals; 30 species of mangrove plants; 287 species of phytoplankton; 79 species of seaweed; 79 species of zooplankton; 196 species of marine fishes; 154 species of corals; and 538 species of zoobenthos. Many of these species are listed in the Red Book of Vietnam as endangered species, included the white-headed or Cat Ba langur (Trachypithecus poliocephalus), a famous endemic species. Human activities have resulted in significantly changes to the landscape end ecosytems of the Cat Ba islands; however, many natural aspects of the islandsd have been preserved. For this reason, the Cat Ba Islands were recognized as a Biological Reserved Area by UNESCO in 2004.

Reproductive parameters of wild Trachypithecus leucocephalus: seasonality, infant mortality and interbirth interval

Understanding the reproductive parameters of endangered primate species is vital for evaluating the status of populations and developing adequate conservation measures. This study provides the first detailed analysis of the reproductive parameters of wild white-headed langurs (Trachypithecus leucocephalus), based on demographic data collected over an 8-year period in the Nongguan Karst Hills in Chongzuo County, Guangxi, China. From 1998 to 2002, a total of 133 live births were recorded in the population based on systematic censuses. Births occurred throughout the year, but the temporal pattern was highly correlated with seasonal variation in temperature and rainfall, with the birth peak coinciding with the dry and cold months of November-March. The average birthrate was 0.47+/-0.13 births per female per year and mortality for infants younger than 20 months was 15.8%. From 1998 to 2006, 14 females gave birth to 41 infants in four focal groups. The average age at first birth for female langurs was 5-6 years (n = 5) and the interbirth interval (IBI) was 23.2+/-5.2 months (median = 24.5 months, n = 27). Infants are weaned at 19-21 months of age. The IBI for females with infant loss before weaning was significantly shorter than those for females whose infants survived. It appears that birth seasonality in the white-headed langurs is influenced by seasonal changes in food availability. The timing of conceptions was found to coincide with peak food availability. The reproductive parameters for white-headed langurs reported here are quite similar to those reported for other colobine species. One major difference is our observation of lower infant mortality in Trachypithecus.

Comparison of locomotor behaviour between white-headed langurs Trachypithecus leucocephalus and François’ langurs T .françoisi in Fusui, China

Abstract We studied the locomotor behaviour of white-headed langurs Trachypithecus leucocephalus and François’ langurs T .françoisi to test two hypotheses: (1) these monkeys have evolved locomotor ability to support their activities on limestone hills, and (2) François’ langurs have evolved more diverse locomotor skills than white-headed langurs. Data were collected from 1996 - 1998 and in 2005 in Fusui Nature Reserve, Guangxi, and showed that the two species had similar locomotor types, but François’ langurs had more locomotor modes (26) than white-headed langurs (12). Quadrupedal walking and leaping were two major types, and white-headed langurs were more arboreal than François’ langurs. We suggest that, while keeping their ancestral locomotor types, the two species have evolved new types allowing them to live on limestone cliffs. Compared to white-headed langurs, François’ langurs have more diverse locomotor modes that probably have allowed them to live in more habitat types. As an evolutionary outcome’ François’ langurs have a larger distribution range.

Lack of Sex-Biased Maternal Investment in spite of a Skewed Birth Sex Ratio in White-Headed Langurs (Trachypithecus leucocephalus)

Numerous hypotheses have been developed to explain sex allocation. In male-dispersing, female cooperatively breeding species, the local resource competition model predicts male-biased birth sex ratio, the local resource enhancement model predicts female-biased birth sex ratio, and the population adjustment model predicts that biased birth sex ratio should not be favored if the two sexes are equally costly to rear. The male quality model predicts that, in polygynous species, females in better physical condition will either produce more sons than daughters or invest more heavily in sons than in daughters. White-headed langurs are a female philopatry and female cooperatively breeding species. During a 11-yr study, a total of 133 births were recorded, among which birth sex ratio (M:F = 73:49) was significantly male-biased. This is consistent with the prediction of the local resource competition model. On the other hand, if mothers balanced their investment between the two sexes, according to Fisher’s population adjustment model, males should be the less-costly-to-rear sex. However, we found no sex difference for infant mortality (12.3% in males and 12.2% in females), and sons induced slightly longer interbirth interval (son: 26.4 ± 1.1 mo, daughter: 24.1 ± 0.6 mo) and lactational period (son: 20.9 ± 1.0 mo, daughters: 19.6 ± 0.5 mo) for their mothers. Thus, the population adjustment model was not supported by this study. The local resource enhancement model was not supported because birth sex ratio did not bias to females who provided more reproductive assistance. On the individual level, probit regression showed no relation between birth sex ratio and group size. Because the group size was considered to be negatively related to female physical condition, our study did not support the male-quality model. We suggested several possibilities to explain these results.

Social organization of white‐headed langurs (Trachypithecus leucocephalus) in the Nongguan Karst Hills, Guangxi, China

The number of males per group is the most variable aspect of primate social organization and is often related to the monopolizability of females, which is mainly determined by the number of females per group and their reproductive synchrony. Colobines show both inter-specific and intra-specific variations in the number of males per group. Compared with other colobine species, little is known about the social organization of white-headed langur (Trachypithecus leucocephalus), despite its endangered status and unusual limestone habitat. As a part of a long-term study of the white-headed langurs in the Nongguan Karst Hills, Guangxi, China, we quantitatively investigated their social organization by analyzing census data from 1998 to 2003. The population censuses revealed that the predominant social organization of bisexual groups was the one-male group, similar to a previous report on this species and many other Asian colobines. In such groups, one adult male associated with 5.1 adult females, 0.1 sub-adult males, 2.6 juveniles and 2.9 infants on average, with a mean group size of 11.7 individuals. In addition, three multi-male groups were recorded, consisting of 2-3 adult males, 1-5 adult females, 0-2 sub-adult males, 0-7 juveniles and 0-2 infants. They did not contain more adult females than the one-male groups and were unstable in group membership. The langurs outside bisexual groups were organized into small nonreproductive groups or lived as solitaries. The nonreproductive groups averaged 1.3 adult males, 1.3 sub-adult males and 2.6 juveniles. Juvenile females were present in such groups on 52.4% of all occasions. As predicted by the monopolization model, the prevalence of the one-male pattern in this species may mainly be attributed to the small number of females in the group. The possible reasons for the occurrence of multi-male groups and the presence of juvenile females in nonreproductive groups are also discussed.

Karst Habitat Fragmentation and the Conservation of the White-Headed Langur (Trachypithecus leucocephalus) in China

The white-headed langur survives in just four karst forest fragments in China: one in the Longgang National Nature Reserve on the border of the counties of Longzhou and Ningming (NS habitat); a second in Chongzuo Banli Provincial Nature Reserve, Chongzuo County (CZ habitat); and two in Fusui Papen Provincial Nature Reserve, Fushui County (F1 habitat and F2 habitat), all in the southwest of Guangxi Province. The population is fewer than 700. We used GIS of Mapinfo Professional 7.0 and Arcview 3.2 to study karst landscape features (forest fragmentation and patchiness of natural formations and those resulting from or affected by human activities) in the known range of the white-headed langur. Results indicated that the NS fragment was the best conserved regarding the presence of natural karst hill system forest and the connectivity of forest habitat, and having the least agriculture. F1 and F2 ranked the second and the third in these aspects, while the CZ forest was the most fragmented and degraded by human activities. Most of the plains in F1, F2 and CZ were cultivated, given over to sugarcane plantations—the most widespread cash crop in the southwest of Guangxi province. The four karst habitats and their populations of white-headed langurs are facing similar problems, most marked in F1, F2 and CZ. Foremost are cultivation and human interference, then firewood collection and illegal hunting. Fortunately, the government has initiated some measures to mitigate the affects of human activities, including clamping down on illegal hunting.

Weaning Age, Infant Care, and Behavioral Development in Trachypithecus leucocephalus

Primate infants are born in an altricial state and rely on the care of their parents for a relatively long period of time. Parental investment is critical to offspring survival and thus to the reproductive success of the parent as well. However, mothers and infants may experience a conflict of interest, in that infants may benefit by receiving prolonged maternal care but mothers may curtail such care in a tradeoff between investment in current versus future offspring. Documenting life history characteristics, such as age at weaning, is important not only for understanding the conflicts of interest and tradeoffs; such information can also provide insights about female reproductive rates and be valuable for conservation efforts. Little is known about the life history of white-headed langurs (Trachypithecus leucocephalus), despite their endangered status. We were the first to investigate mother-infant relationships and infant behavioral development in the species. We studied 3 wild mother-infant pairs throughout infancy. We used data from >460 h of focal subject sampling to calculate the proportion of time individuals spent in different behavioral states and the frequency of instantaneous events, such as maternal rejection. White-headed langur infants depended on their mothers for 19–21 mo, at which time they were weaned. Maternal rejection facilitated infant independence in the early stages of infant development, and mothers stopped investing in their infants when they resumed estrus. The weaning age of the wild white-headed langurs we studied was dramatically longer than that of captives, possibly as a result of the nutritional differences between wild and captive populations. Weaning age was also longer than for most other Asian colobines, and may be attributable to the degradation and fragmentation of their natural habitat.

Feeding strategy of François' langur and white‐headed langur at Fusui, China

We investigated the diet of a group of François' langur inhabiting a forest fragment between August 2002 and July 2003 to add to our knowledge of behavior and ecology of this langur. Our objective was to study whether the François' langur would adopt a feeding strategy similar to the white-headed langur in the same nature reserve. Data indicated that a total of 37 plant species were eaten by François' langur; however, only ten species accounted for 90% of the total feeding time. Four species belong to the ten most dominant tree species within the vegetation quadrats. Ninety-four percent of feeding time of François' langur was spent on leaves, whereas the remaining 6% of time was spent on fruits, flowers and twigs. Results also demonstrated that François' langur are similar to white-headed langur in being predominantly folivorous and that Francois' langur adopted a similar strategy to white-headed langur in diet, dietary variation and time spent on feeding. François' langur exhibited a habitat use preference for the middle zone of the forest, whereas the white-headed langur utilized the bottom zone of the forest. Further analysis indicates that human interference and habitat fragmentation caused by agriculture also impact habitat use.

Food Items Consumed by White-headed Langurs in Fusui, China

We studied the socioecology of white-headed langurs (Trachypithecus leucocephalus) from September 1997 to September 1998 in Fusui Precious Animal Reserve, SW Guangxi, China. We collected data on climate, phenology of food plant species, and foods consumed by langurs living in habitats with different levels of human disturbance. Feeding records showed that the most food is from less common plant species. Young leaves were the staple food item in all langur groups, and consumption correlates with availability. Consumption of mature leaves is not significantly correlated with their availability, but the langurs fed on them, and other food items such as fruits and seeds, when the availability of young leaves was low. Langurs in different areas had broadly similar diets, but they varied most in the proportion of supplementary items such as fruit. Groups in more disturbed habitat did not increase the overall proportion of mature leaves in their diet, but instead maintained their intake of young leaves from a greater diversity of species, and incorporated more immature fruit. Conservationists should direct efforts toward protection of rare plant species providing preferred food items, particularly supplementary foods at times when, and in areas where, preferred food items are less available.

Male–immature interactions seem to depend on group composition in white-headed langur (Trachypithecus leucocephalus)

In primates, male–immature interactions are always multifacetted. We studied male–immature interactions of white-headed langur during our long-term study in Nongguan White-Headed Langur Reserve, Guangxi, China. Male–immature interactions obviously differed between one-male groups and male–immature groups. In one-male groups, adult males behaved tolerantly or aggressively towards immatures and never carried out sociopositive behaviors. Sexual selection theory supports this phenomenon because males are predicted to bias to compete for more mating chances but not to invest in any single offspring. In male–immature groups, however, adult males carried out sociopositive behaviors and never behaved aggressively towards immatures. This is supported by kin selection theory because it will be beneficial for the males to increase the survival of the immatures if they are likely the fathers of them. Thus, we conclude that male–immature interactions differ between one-male groups and male–immature groups because the mating status of males are different between the two kinds of groups.