habitat quality and range use of white&hyphen;headed langurs in fusui, china

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Dr. Zhaoyuan Li, Faculty of Conservation Biology Southwest Forestry College, Bailongsi, Kunming Yunnan 650224 (PR China) Tel./Fax +86 871 582 3980 E-Mail [email protected]

Original Article

Folia Primatol 2005;76:185–195 Received: September 2, 2003 DOI: 10.1159/000086020 Accepted after revision: October 3, 2004

Habitat Quality and Range Use of White-Headed Langurs in Fusui, China

Zhaoyuan Lia M. Elizabeth Rogersb aFaculty of Conservation Biology, Southwest Forestry College, Kunming, China; bICAPB, University of Edinburgh, Edinburgh, UK

Key Words White-headed langur � Trachypithecus leucocephalus � Group size adaptation ��Range size variation � Habitat quality

Abstract The socioecology of white-headed langurs (Trachypithecus leucocephalus)

was studied in Fusui Precious Animal Reserve, Guangxi, China, in 1997/1998. Habitat quality was classified according to the level of human disturbance. Plant species diversity increased with habitat quality. Important foods for the langurs occurred more in high-quality habitat. Home range size varied from 28 to 48 ha, and the home range area per individual decreased as habitat quality increased. Small polygynous langur groups had poorly defended ranges, but large groups defended their ranges intensively. Only harem males were involved in group defence, apparently competing for females by defending their habitat. High-quality habitat was more attractive to females; accordingly, group size increased significantly with habitat quality.

Introduction

Range sizes are extremely variable, both within and between species and gen-era of Asian colobines [Poirier, 1968; Horwich, 1972; Mukherjee and Saha, 1974; Hladik, 1977; Oppenheimer, 1977; Curtin, 1980; MacKinnon and MacKinnon, 1980; Islam and Husain, 1982; Davies, 1984; Bennett, 1986; Johns, 1986; Newton, 1987; Kool, 1989; Stanford, 1991; Bennett and Davies, 1994]. For example, the home range of Hanuman langurs (Semnopithecus entellus) is only 4 ha in villages and farms, 20 ha in dry deciduous forest, 60–96 ha at the edge between grassland and forest and 390 ha in moist deciduous forest [Oppenheimer, 1977; Newton,

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http://dx.doi.org/10.1159%2F000086020

186 Folia Primatol 2005;76:185–195 Li/Rogers

1987]. Bennett and Davies [1994] suggest that such variation is an adaptation to different habitat types, because, in addition to variations in home range size, lan-gurs also vary in other respects, including body size, group size and population density. Differences in home range size in other colobine species are also attributed to variation in habitat types [Bennett and Davies, 1994]. There are no studies in which the range sizes of colobines have been analysed specifically in relation to anthropogenic habitat degradation. Furuichi et al. [1982] proposed an elastic enclo-sure model to describe the relationship between home range size and habitat quality in Macaca fuscata, which predicted that home range size will increase with the size of animal groups in homogeneous habitat and decrease with increasing habitat qual-ity if the group size stays constant. However, in disturbed habitat which is hetero-geneous and fragmented, such models cannot predict range size; so, analyses of the effects of disturbance on ranging are of vital predictive value to the future conser-vation of primates.

White-headed langurs (Trachypithecus leucocephalus), one of the 25 most en-dangered primate species in the world, are found in Fusui Precious Animal Reserve in Fusui County, Chongzuo Precious Animal Reserve in Chongzuo County and Longgang National Nature Reserve, south-west Guangxi, China [Li et al., 2003a]. Their world population size was reported to be 866 in the late 1970s [Li and Shen, 1982], 400 at the beginning of the 1980s [Wu, 1983], some 700 in 1987 [Lai, pers. commun.] and no more than 500 in 1997 [Li et al., 2003a]. In addition to poaching, habitat loss and degradation are also responsible for the population decline since 1990 [Li et al., 2003a]. We have studied the impacts of habitat degradation on the reproduction of the langurs in Fusui Reserve [Rogers and Li, 2002], on activities [Li and Rogers, 2004a], on food choice [Li et al., 2003b] and on social organization [Li and Rogers, 2004b]. In this paper, we document the negative influence of habitat degradation on the range use of white-headed langurs in Fusui Reserve.

Methods

Study Site The study site (532 ha; about 22º27' N and 107º52' E; 110–359 m above sea level) was

located in the central part of a group of limestone hills, called LGS, in Fusui Reserve [Li et al., 2003a]. The topography is characterized by steep cliffs that often prevent observers from following langur groups in some valleys. From 1988 to 1998, 86.7% of the land in the study site was lost to year-round or seasonal agricultural use, and only 13.3% had not been used or had reverted to use by langurs [Li, 2000]. From December 1997 to July 1998, seven patches of land were cleared for cultivation, ranging from 0.001 to 2.5 ha in patch size, with a total area of 3.8 ha. Based on the degree of human disturbance and the remaining natural vegeta-tion, the habitat was scored into 4 classes: class IV habitat (best quality, scored 4; totalling 45.2 ha or 8.5% of the total area of the study site), in which the flat ground between hills still had natural vegetation and the valleys were relatively closed and infrequently visited by people; class III habitat (scored 3; 57.9 ha or 10.9%), in which the flat land was partly vege-tated and not used by farmers, but firewood was sometimes collected there for cooking; class II habitat (scored 2; 163.5 ha or 30.7%), in which farmers used the flat land seasonally, vegetation covered foothills and firewood was collected more often; class I habitat (lowest quality, scored 1; 265.5 ha or 49.9%), characterized by foothills where vegetation had been cleared, flat land was farmed year-round and there was a high frequency of firewood collec-tion (almost every day). When there was more than one class of habitat in the range of a langur group, the class of the larger component was recorded for that group (table 1).

Range Use of White-Headed Langurs 187 Folia Primatol 2005;76:185–195

Plant Species Composition Plant species composition was investigated in March and April 1998. Vegetation cov-

ered only the limestone hills and part of the valley floor, so the forest edge extended along a line at varying distances from the base of the vertical cliffs. Sampling occurred every 50 m along the edge line. At each sample point, a perpendicular transect was marked by a rope pulled from the forest edge to the hill foot. Transect length varied with distance between the forest edge and the foot of the cliff, with a maximum length of 50 m. A total of 311 transects were surveyed in a total area of 11.603 ha. Trees and woody lianas ≥1.2 cm dbh within 5 m to either side of the rope were recorded. Species were identified by a botanist from Guangxi Institute of Botany [S. Lin, pers. commun.]. The lower limit of 1.2 cm dbh was determined because langurs had been seen in shrubs of this size and larger [Li, 1993].

Range Size of Langur Groups White-headed langurs lived solitarily, in all-male bands, multi-male/multi-female

groups and polygynous groups [Li and Rogers, 2004b]. A polygynous group, also called a harem group, consisted of one breeding male, several breeding females and their offspring. We collected data from September 1997 to September 1998. A total of 13 langur groups were identified. Of these, 9 were polygynous (table 1), indicating that polygyny was the typical mating system [Li and Rogers, 2004b]. These groups were the subjects for our obser-vations. Group GA4 split into two (GA4-A and GA4-B) after a group take-over had occurred between December 1997 and January 1998. GA1 and GA4-B were all-male bands and GA4-A was a multi-male/multi-female group. GAF was a polygynous group, consisting of an adult male and 2 female white-headed langurs, their offspring and an adult François’ langur female (T. françoisi) [Li and Rogers, 2004b]. We collected behavioural data for ≥15 days/month. Different langur groups were observed for different amounts of time, depending on the frequency of group encounters [Li and Rogers, 2004a]. During daily observation, the position of each study group was plotted once every 30 min on maps scaled 1/5,000 [Li, 2000]. Observation periods varied between 0.5 and 6 h, because the langur groups often moved out of sight. Data on intergroup interactions were collected using ad libitum sampling [Altmann, 1974]. Ninety-four percent of the positional records were collected during sys-tematic observations; the remaining 6% were collected opportunistically. The range of each

Table 1. Group composition, range, and habitat quality of polygynous groups of white-headed langurs

Range overlap(%)3 Groups Records (point locations)

Mean group size1

No. of infants &juveniles

Habitat qualityscores

Range size(ha) [area/ individual]2 GA2 GA3 GA4 GA5 GA6 GA7 GA8 GALN GAGL

GA2 82 6.0 0 2 32 [5.3] 0 0 0 0 0 0 0 0 GA3 218 14.5 7 4 32 [2.2] 0 37.5 0 0 9.0 1.8 0 0 GA4 145 10.0 2 3 48 [4.8] 0 25.0 0 0 30.0 32.1 0 0 GA5 54 7.5 2 3 26 [3.5] 0 0 0 0 13.8 5.4 0 0 GA6 11 11.5 6 4 16 [1.4] 0 0 0 0 0 0 0 0 GA7 55 9.5 3 3 36 [3.8] 0 8.0 40.0 10.0 0 25.7 0 0 GA8 164 4.5 0 1 28 [6.2] 0 2.0 55.0 5.0 0 33.0 0 0 GALN 12 12.0 7 4 27 [2.3] 0 0 0 0 0 0 0 0 GAGL 7 4.0 0 1 17 [4.2] 0 0 0 0 0 0 0 0

1 With social dynamics, group size often changed. Thus, only mean group size is provided here. 2 Range size estimates for groups GA2, GA3, GA4, and GA8 were based on > 86 positional records, which was the cut-off

point (see text & Fig. 2), so only data from these groups were used for further comparison in Table 2. Figures in brackets are the range area per individual.

3 Numbers in the range overlap cells show pairwise % overlap between the two langur groups in each row and column. Data in these cells are rough estimates of home range overlap, because group range sizes will enlarge with more observations, especially for groups with only a few records.


study group was demarcated using a grid of 1-ha squares superimposed on the maps. A modified minimum convex polygon method was used to calculate ranges, which involved first connecting the outer points of each group’s range and then eliminating any included squares of unsuitable habitat avoided by langurs (i.e. some flat land between hills).

Data Analyses When analysing food choice [Li et al., 2003b], we defined highly preferred species as

those with a selectivity index ≥10 (selectivity index: percent of a given species in feeding records divided by percent of that species in the habitat). Data on the frequency of plant spe-cies were transformed into Shannon-Weaver indices of plant species diversity [Shannon and Weaver, 1949]. Pearson product moment correlation coefficient (R) and Spearman rank corre-lation coefficient (rs) were used to test correlations between factors [Fowler et al., 1998].

Results

Habitat Quality and Plant Species Diversity Along the 311 transects, we recorded 13,204 plants, belonging to 164 species

and 112 genera from 48 families [Li et al., 2003b]. The top 20 commonest species accounted for 65.5% of the total number of plants, but only 12.2% of the total num-ber of species. The commonest species were found more in habitat class III. The dominant families, containing 51.0% of the total individuals, were the Euphor-biaceae, the Lauraceae, the Moraceae and the Sterculiaceae [Li et al., 2003b]. The commonest species, accounting for 25.0% of the plants, were Oroxylum indicum (Bignoniaceae), Pteroceltis tatarinowii (Ulmaceae) and Cipadessa cinerascens (Meliaceae). Less common species tended to occur more in less disturbed habitats (classes IV and III), and plant species diversity increased with habitat quality (rs = 0.347, n = 24, one-tailed, p < 0.05).

Fifty plant species were recorded as foods, belonging to 42 genera from 28 families [Li et al., 2003b]. No highly preferred food species was among the 20 commonest species in the habitat. Some species were present in the diet of the lan-gurs all year round and were classified as staple species. Those species appearing in the diet only in the lean season (December 1997 to February 1998) were classified as fallback species. Six species provided key plant resources to the langurs, in that they sustained them during the lean season, and thus were called key species [Li et al., 2003b]. Key and staple species were defined as important species because of their significance to the survival of the langurs. There were 16 important species, 4 of which (Sageretia hamosa, Pueraria thunbergiana, Broussonetia kazinoki, Tet-racera asiatica) were found only in high-quality habitat (classes III and IV). The

Fig. 1. Range distribution of the main study groups of white-headed langurs in the hill group LGS, Fusui Reserve. a Groups GA2, GA3, GA6, GA8, GAF, GAGL and GALN. b Groups GA4 and GA7. Ranges of groups GA1 and GA5 not shown for clarity: they par-tially overlap the ranges of GA4, GA6, GA7 and GA8. In b, an apparent overlap area (cross-hatched) is shown between GA4 and GA7, because GA7 extended its range into the former range of GA4 after the latter had split into GA4-A and GA4-B, which were both excluded by GA7 (see text).


a

b


frequency of important species varied, but most individuals occurred in high-quality habitat, indicating that more important food resources were available there [Li et al., 2003b].

Range Use of Langur Groups During the 13-month observation period, a total of 748 point locations were

mapped for the 9 polygynous groups living in different quality habitats and differ-ently sized ranges (table 1). It was found that all-male bands, GA1 and GA4-B, had large ranges, but they did not defend them. Large polygynous groups, such as GA3 and GALN, had well-defended ranges. In contrast, small polygynous groups (e.g. GA8) had poorly defended ranges. When all-male bands stayed in GA3’s range, the harem male of GA3 chased them out of his group’s range. But GA8 shared its range with all-male bands if the distance between them was ≥150 m. The ranges of polygy-nous groups overlapped spatially but not temporally, i.e. invaders stayed in a range only when the owner was absent. GA4 overlapped in range extensively with GA3, GA7 and GA8, because the latter groups extended their home ranges into the home range of GA4 after GA4 had split into two. The range of GA4 covered two thirds of the valley LG, all of the valley LY1 and parts of the valleys LH, LL and LY2 (fig. 1). Male replacement occurred in the group between December 1997 and January 1998, and the group split into GA4-A and GA4-B [Li and Rogers, 2004b], after which GA7 invaded, occupying all of LY1 and parts of LG, LH and LY2 (fig. 1b) and excluding GA4-A and GA4-B. With the disappearance of GA4, GA3 and GA8 extended their ranges into GA4’s range in LG and met at the site of 3B8 (fig. 1a). GA7 overlapped with GA5 in a broad area, because the former group excluded the latter from its origi-nal home range and took over part of it. Another broad overlap was between GA7 and GA8, where GA7 spent little time in the area of overlap, which was low-quality habi-tat, and GA8 avoided GA7 in the overlap area. Thus, extensive overlaps in all these cases did not indicate great tolerance between langur groups. In most other cases, home ranges overlapped little, indicating intergroup intolerance.

Langur ranges changed with human disturbance. In January 1998, villagers cleared all vegetation in an area of 1 ha on the slope between the hill DTS and other hills in the valley LWG for planting sugar cane (fig. 1). After that, GA2 did not use DTS for 7 months until a new male from outside took over the group in early Au-gust 1998 [Li and Rogers, 2004b].

Habitat Quality and Home Range of Langur Groups Estimates of range size will increase with observation time, because food re-

sources are not evenly distributed. Group GA8 lived in flat terrain and could be followed in any part of its home range, so we used the data from this group to esti-mate the number of records needed for demarcating its entire home range. Figure 2 shows that the range size of GA8 did not increase further after 86 point locations had been obtained. The Pearson correlation test did not show a significant correla-tion between the number of records and the range size of the 9 groups in table 1 (R = 0.525, n = 9, two-tailed, p = 0.147). This indicated that range size was not significantly influenced by the number of observations beyond a certain point, though further observation on some groups might reveal some increase. Thus, the cut-off point of 86 records was used. Accordingly, the home ranges of GA2, GA3, GA4 and GA8 could be determined, because the number of records for these groups


was close to or greater than 86 (table 1) and they showed a similar relationship be-tween range size and the number of records.

Transects in the home range of GA3, in the highest-quality habitat (scored 4), contained 79 plant species belonging to 62 genera from 34 families, whereas those in the range of GA8, in the lowest-quality habitat (scored 1), contained 96 species belonging to 77 genera from 35 families. Both ranges contained 12–13 of the 16 important food plant species. However, whereas there were 432 individuals of these important species, accounting for 28.7% of plants (n = 1,503) recorded on the tran-sects in the home range of GA3, there were only 286 individuals recorded in that of GA8, accounting for 19.3% of plants recorded (n = 1,482). This indicates that high-quality habitat provided more food resources to GA3.

In polygynous groups, the harem males defended their home range. Accord-ingly, it was predicted that the number of females a harem male could monopolize, and hence the number of offspring he could sire, would increase with increasing habitat quality, which was supported by a strong correlation between habitat quality and group size (rs = 0.888, n = 9, one-tailed, p < 0.005), and also between habitat quality and the number of infants and juveniles in each group (rs = 0.908, n = 9, one-tailed, p < 0.005). Only the langur groups living in habitat classes II–IV (scored 2–4) had offspring, and the area involved accounted for 50.1% of the study site. Home range size increased with habitat quality (fig. 3) and decreased with increasing food plant species diversity in the diet (fig. 4). However, because the sample size was small (n = 4), the significance of these correlations could not be tested. The relationship between home range size and habitat quality is complicated by the fact that langur groups were larger in higher-quality habitat. However, if group size is corrected for by calculating range area per individual, there is an in-verse relationship between area per individual and habitat quality in groups GA2, 3, 4 and 8 whose range sizes were most accurately estimated (fig. 3). Thus, individu-als in low-quality habitat require a greater area for survival and must eat food from more species of plants. Therefore, langur groups in lower-quality habitats had greater species diversity in their diet than those in higher-quality habitats.

Fig. 2. Relationship between home range size (each grid square = 1 ha) and accumulativepositional records (point locations) of white-headed langurs. Data from group GA8.


Range Defence White-headed langur groups responded to other groups nearby with different

intensity. The first type of response was that the harem male stared at the neighbouring group without further action, which occurred in 52% of systematic records of group encounters (n = 23). The second type was a more obvious display, where the harem male of the larger group emitted loud calls, ran about in the trees and shook branches. This response was seen in 17% of the records. In the third type of response, the harem male first performed the display behaviour and then rushed toward the invaders, who then left. When a large group (e.g. GA3) stayed in an-other large group’s (e.g. GA7) home range and was detected by the range owner (n = 1), the invader left the range before being chased. Large groups did not forage in the ranges of small groups, but small groups often foraged in the ranges of large groups (n = 30), indicating that the home ranges of large groups were more attrac-

Fig. 3. Relationships between habitat quality, home range size (solid line) and area per individual (dotted line). Data from GA2, GA3, GA4 and GA8.

Fig. 4. Relationship between food plant species diversity and home range size. Data on food plant species diversity from GA2, GA3, GA4 and GA8 [Li et al., 2003b].


tive in terms of food resources. GA3 and GA8 met at the site 3B8 (fig. 1). In all systematic records of intergroup interactions between the two groups (n = 17), GA8 entered the home range of GA3 only when GA3 was absent, but GA3 was never seen entering the range of GA8, whether GA8 was absent or not. When invasion by GA8 was detected, GA3 chased the invaders and stopped at the site 3B8.

Discussion

Comparison with Other Trachypithecus Species Table 2 shows a comparison of home range size between white-headed langurs

and other Trachypithecus species. The home range size of white-headed langurs in Fusui falls within the range variation of these species. It can be seen that home range size varies remarkably within and between species, suggesting that it can be explained by differences in habitat type [Bennett and Davies, 1994]. None of the studies cited investigated the relationship between range size variation and habitat quality, whereas this study explores distinct effects of anthropogenic habitat distur-bance on range use.

Habitat Quality and Range Competition in White-Headed Langurs It was the harem male who defended the home range of a polygynous group in

white-headed langurs. During intergroup encounters, only the harem males from the two groups in conflict were involved and all other group members remained behind. This indicates that male langurs competed for females by defending home ranges. It has been shown that home ranges in high-quality habitats (e.g. GA3’s home range) provided more food resources and were more attractive to females than those in low-quality habitats (e.g. GA8’s home range). Thus, the size of groups living in high-quality habitats was larger, with more females and their off-spring. The harem males in high-quality habitats tended to occupy large home ranges, by which more individuals could be supported, although the area per indi-vidual was actually smaller than for groups in low-quality habitat. White-headed langurs fed selectively on rare plants [Li et al., 2003b]. In high-quality habitats, there were more individuals of important food plants, so langur groups obtained more food from them (e.g. 66.2% of GA3 feeding records) than those in low-

Table 2. Home range size of Trachypithecus leaf monkey species

Species Range size, ha Reference T. auratus 2.5–8 Kool [1989] T. geei 64 Mukherjee and Saha [1974]; Islam and Husain [1982] T. johnii 5.6–240 Poirier [1968]; Horwich [1972] T. leucocephalus 28–48 Present study T. obscurus 33 Curtin [1980]; MacKinnon and MacKinnon [1980] T. phayrei 30–128 Bennett and Davies [1994]; Zheng [1993] T. pileatus 14–24 Stanford [1991] T. vetulus 2–3 Hladik [1977]


quality habitat (e.g. GA8, 59.2%) [Li et al., 2003b]. In other words, white-headed langurs in high-quality habitats could concentrate their feeding on more preferred foods and needed less area per individual, whereas those in low-quality habitats had to feed on other foods as well and needed a larger area per individual. In low-quality habitats, because of fewer preferred foods, langur groups had larger home ranges, but they did not defend them (e.g. the tolerance of GA8 to the presence of all-male bands in its range). Instead, they extracted food resources from high-quality habitat that was occupied by a neighbouring large langur group, which caused home range overlap (e.g. GA3 and GA8).

Difference in habitat quality may have resulted in differential reproductive success, because langur groups in habitat class I had stopped their reproduction in the study site in 1997–1998 [Rogers and Li, 2002] and the number of infants and juveniles increased with increasing habitat quality (table 1). It may have also caused a change from polygyny to a multi-male/multi-female mating system in one group [Li and Rogers, 2004b]. Thus, white-headed langur groups were competing for habitats with less human disturbance, and habitat quality has become a key fac-tor influencing the future of the population of white-headed langurs. Accordingly, we have recommended that tree felling be stopped so that plant species diversity (especially the rare species) can recover, and the conservation management of white-headed langurs in Fusui can have a better chance of success [Li, 2002].

Acknowledgements

This study was financially supported by Primate Conservation Inc. (US), the Wenner-Gren Foundation (grant DCTF-60, US), Earthwatch (US), the Wildlife Conservation Society (US), the National Geographic Society (grant No. 6093-97, US), the LSB Leakey Trust (UK), the American Society of Primatologists, the International Primate Protection League (US), the Davis Expedition Fund and the Moray Endowment Fund (University of Edin-burgh), the Georgina Dasilva Award of the Primate Society of Great Britain, Kadoorie Farm and Botanic Garden (Hong Kong) and the Overseas Research Student Scheme (UK).

Thanks go to Mr. Lu Qiang and He Jie (local assistants) for daily assistance in the field, Prof. Shengqiu Lin (Guangxi Institute of Botany, Chinese Academy of Sciences) for identifying plants in the field, Mr. Houxiong Zhou for making maps for the paper, and all volunteers who assisted with the fieldwork. Special thanks are given to Dr. Ardith Eudey (Asian Primate Specialist Group), Dr. John Fellowes (Kadoorie Farm and Botanic Garden), Dr. William Bleisch (Wildlife Conservation Society), Prof. Ramon Rhine (University of California) and Prof. Aubrey Manning (University of Edinburgh) for help in finding finan-cial support, and Prof. Warren Y. Brockelman, Dr. S. Srikosamatara (Mahidol University, Bangkok) and Dr. John Deag (University of Edinburgh) for their help in the early conception of the research project. We are grateful to the anonymous reviewers for their valuable com-ments.

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habitat quality and range use of white&hyphen;headed langurs in fusui, china

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