A Newly-Found Pattern of Social Relationships Among Adults Within

Home , Gelada, Golden monkey, Hamadryas baboon

Integrative Zoology 2013; 8: 400–409 doi: 10.1111/1749-4877.12026

1 ORIGINAL ARTICLE 1 2 2 3 3 4 4 5 5 6 A newly-found pattern of social relationships among adults within 6 7 7 8 one-male units of golden snub-nosed monkeys (Rhinopithecus 8 9 9 10 roxenalla) in the Qinling mountains, China 10 11 11 12 12 13 13 1, 1,2, 2 2 1 14 Xiaowei WANG, * Chengliang WANG, * Xiaoguang QI, Songtao GUO, Haitao ZHAO, 14 15 Baoguo LI1,2 15 16 16 1 2 17 Institute of Zoology, Shaanxi Academy of Sciences, Xi’an, China and College of Life Sciences, Northwest University, Xi’an, China 17 18 18 19 19 20 20 21 Abstract 21 22 Group living provides various advantages to individuals in regards to protection avoidance, intergroup competi- 22 23 tion, productive success and social information. Stable one-male units (OMUs) consist of relationships between 23 24 the adult females and the resident male as well as the relationships among adult females. Based on continuous 24 25 observation of a reproductive group of golden snub-nosed monkeys (Rhinopithecus roxellana) in the Qinling 25 26 mountains, we analyzed the relationships among adult individual dyads within 4 OMUs. The results indicat- 26 27 ed that in golden snub-nosed monkey societies, females not only had no strong tendency to build a relationship 27 28 with the resident male in the OMU but also had no strong tendency to build relationships with other females 28 29 in the OMU. In comparison with hamadryas (Papio hamadryas) and gelada baboons (Theropithecus gelada), 29 30 the relationships within golden snub-nosed monkeys OMUs showed neither the star-shaped pattern observed in 30 31 hamadryas baboons nor the net-shaped pattern observed in gelada baboons. We concluded that the relationships 31 32 within golden snub-nosed monkey OMUs indicated a third pattern in nonhuman primate societies. Future re- 32 33 search is required to determine the potential mechanisms for such a pattern. 33 34 34 35 Key words: adult dyad relationships, golden snub-nosed monkey, one-male unit, patterns of social relationships, 35 36 Rhinopithecus roxellana 36 37 37 38 38 39 39 40 40 ness against conspecific groups for resources, and better 41 INTRODUCTION 41 breeding and exchange of information (Danchin et al. 42 42 Group living provides various advantages to individ- 2005; Meunier et al. 2006). However, spatial proximi- 43 43 uals, such as predator protection, improved competive- ty is commonly associated with inter-individual compe- 44 44 tition for limited resources. If individuals have different 45 45 needs and motivations, the group may lose cohesion and 46 46 Correspondence: Xiaoguang Qi and Baoguo Li, College of separate, thus negating the advantages of group living 47 47 (Krause & Ruxton 2002; Leca et al. 2003; Meunier et 48 Life Sciences, Northwest University, North Taibai Road No. 48 al. 2006). The advantages of group living are achieved 49 229, Xi’an, Shaanxi 710069, China. 49 only if the group maintains cohesion by developing and 50 Email: [email protected]; [email protected] 50 sustaining relationships among individuals. Based on 51 *These authors contributed equally to this work. 51

400 © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS OMUs of golden snub-nosed monkeys previous research, 2 social relationship patterns that cre- OMUs forming a band, and a number of bands, in- 1 ate stability among group-living individuals have been cluding AMUs, forming the troop (Kirkpatrick et al. 2 described in hamadryas baboons [Papio hamadryas 1998; Ren et al. 2000; Zhang et al. 2006, 2008; Qi et 3 (Linnaeus, 1758)] and gelada baboons [Theropithecus al. 2009). The size of troops in this species common- 4 gelada (Rüppel, 1835)]. ly ranges from 100 to 300 individuals, which are much 5 Both baboon species live in multi-level societies, in larger than groups of most other Asian colobines (Chen 6 which individual relationships are implemented at 2 or et al. 1989). Adolescent males transfer from their na- 7 more levels within the community (Kummer 1968; Dun- tal unit into an AMU before reaching sexual maturi- 8 bar 1979; Mori 1979a; Sigg et. al. 1982; Kawai 1990; ty, while females may remain in their natal unit (Chen 9 Swedell 2002). In baboons, Kummer (1968) and Abeg- et al. 1989; Ren et al. 2000). Researchers have long as- 10 glen (1984) suggest that one-male units (OMUs), which sumed that this species lives in female relationship so- 11 consist of 1 resident male, many females, their offspring cieties, based on frequently-observed affiliative inter- 12 and sometimes more than 1 follower male, is the small- actions among females in captive groups (Chen et al. 13 est and most stable social unit. The OMU forms the 1989; Ren et al. 2000). Recently, however, research- 14 foundation for their multi-level society, whereby many ers have reported that both adolescent male and female 15 OMUs come together to form a band, and many bands golden snub-nosed monkeys transfer among OMUs 16 form a troop (Qi 2010). Although hamadryas and gela- in the wild. Adolescent males transfer from the natal 17 da baboons exhibit the same social system, the social re- unit to an AMU, and females not only transfer between 18 lationships among the individuals, which keep the OMU OMUs in the same band, but they transfer among differ- 19 stable, are quite variable. ent troops as well (Zhang et al. 2008; Qi et al. 2009). In 20 The relationship among hamadryas baboon individ- addition, some observations, such as inter-unit copula- 21 uals within an OMU is defined as a star-shaped rela- tions (Zhao et al. 2005) and disappearance of adult fe- 22 tionship (Kummer 1968). In each OMU, only 1 resident males (Zhang et al. 2006), now bring into question the 23 male actively guards and copulates with the females previous assumption that golden monkeys are a female 24 (Abegglen 1984). Females frequently transfer between relationship-based species (Chen et al. 1989; Ren et al. 25 different OMUs (Kummer 1968) and each female has 2000). 26 a far stronger relationship with her resident male than In this study, we aimed to test the relationship di- 27 with any other adult members in her unit. These rela- versity among adult individual dyads of golden snub- 28 tionships are expressed in the tendency to predominant- nosed monkeys. Based on proximity and grooming data 29 ly groom and interact with the resident male and rarely among female dyads and among female and resident 30 with other females (Swedell 2002). This indicates that male dyads across 4 OMUs, we compared the individu- 31 hamadryas baboon OMUs are formed by male sexual al relationships among the hamadryas baboons and ge- 32 attraction (Bachmann & Kummer 1980). lada baboons. 33 34 The relationship among gelada baboon individu- 35 als within an OMU is defined as a net-shaped relation- MATERIALS AND METHODS 36 ship (Mori 1979a). In each OMU, only the resident male 37 copulates with adult females and adolescent males trans- Study site and subjects 38 fer from their natal unit into an all-male unit (AMU) be- This study was conducted in an area surrounding the 39 fore they reach sexual maturity (Mori 1979b). Females Yuhuangmiao village in Zhouzhi National Nature Re- 40 remain in their natal unit (Kawai et al. 1983). Only 1 serve, located in the Qinling mountains, Shaanxi, Chi- 41 adult alpha female builds a relationship with the resident na (33°48′68″N, 108°16′18″E). Details on local ecology 42 male, while the other females build relationships with and topography have been described previously (Li et 43 each other (Dunbar 1983b). Thus, the gelada baboon al. 2000). 44 OMUs are formed by kinship among females (Seyfarth 45 1976; Mori 1979b). There are 2 groups of golden snub-nosed monkeys inhabiting the study area, the East Ridge Group and the 46 Another multi-level society species is the golden West Ridge Group which are separated by the Nancha 47 snub-nosed monkey (Rhinopithecus roxellana Milne- River. We studied the West Ridge Group, which consist- 48 Edwards, 1897) (Zhang et al. 2006, 2008; Qi et al. ed of 6–8 OMUs. Proximity observation during provi- 49 2009, 2010). According to previous studies on this spe- sioning allowed all adult individuals to be individual- 50 cies, their OMUs form the basic social unit, with many 51

1 Table 1 The age–sex class composition of study group 2 Adult male Adult female Subadult Juvenile Infant Total 3 Luo Pan (LP) 6 3 5 3 18 4 5 Jia Ban (JB) 5 1 4 3 14 6 Ba Zi Tou (BZT) 5 4 5 1 16 7 Rui Xing (RX) 4 0 2 1 8 8 9 Recorded from Sep 2007 to Jun 2008 10 11 12 13 ly identified by physical differences (Qi et al. 2004; Li If 2 adults were grooming one another or 1 was being 14 et al. 2006; Zhang et al. 2006). The age–sex classes of groomed by the other, they must obviously sit in close 15 the golden snub-nosed monkeys include resident males, proximity to each other. These occurrences were only 16 adult females, subadults, juveniles and newborn babies recorded as ‘grooming’ or ‘being groomed’; they were 17 (Zhang et al. 2006) (see Table 1). not also recorded as ‘sitting proximity’. 18 19 Data collection Data analysis 20 Data were collected from Sep 2007 to Jun 2008. On We excluded analyses of juveniles and infants in this 21 each working day, observations started at 0900 hours 22 study because: (i) we could reliably not identify these and finished at 1600 hours when the group began to 23 individuals and (ii) their spatial distribution in the unit move for feeding freely in the wild and in search of 24 was highly dependent on their mothers. Thus, data was their overnight sleeping site (Li et al. 2004). We ob- 25 collected from 20 females and 4 resident males across served only 1 OMU per day with a total of 4 OMUs ob- 26 4 OMUs. The frequency of each behavior for each indi- served over the course of the study. On each working 27 vidual and for each OMU is summarized in Table 2. day, when the target OMU came into view, scan sam- 28 pling was immediately conducted (Altmann 1974), with 29 Proximity, grooming and being groomed indexes information concerning the activity of all members re- 30 among individual dyads within 4 one-male units corded. Scans were repeated at 5 min intervals for as 31 long as the OMU was in view. If the focal OMU moved To compare the relationships among individuals in 32 out of view, the observation site was adjusted to allow each OMU according to social activities, we standard- 33 for continued data collection. The spatial proximity cri- 34 ized the individual dyad relationships using 3 indexes; terion was defined as animals within 50 cm of each oth- 35 that is, a proximity index, a grooming index and a being er at the time of sampling. For the golden snub-nosed 36 groomed index. Each dyad for each index was quanti- monkey, an arm length is 52.6 ± 5.94 cm (Liu 1989) and 37 fied as follows: 1 or several adult animals could satisfy 50 cm as spatial 38 proximity criterion at any given sampling time. [F (B)] + [F (A)] 39 Index = A B , 40 Specific individuals’ activities were categorized into [F(A)+ F(B)]

41 4 types, defined as: where F(A) and F(B) are the total number of scans of A 42 Sitting alone: the target adult individual sat with torso and B for a specific phase, that is, proximity, grooming 43 >50 cm from any other adult (i.e. not interacting so- 44 cially). and being groomed, respectively; FA(B) is the number of scans in which B was the partner in social activities 45 Sitting proximity (or proximity): the target adult indi- 46 vidual sat with torso ≤50 cm of another adult. with A when A was scanned, and FB(A) is the number of scans in which A was the partner in social activities with 47 Grooming: the target adult individual groomed another 48 adult individual. B when B was scanned. We calculated the proximity in- 49 dex, the grooming index and the being groomed index Being groomed: the target adult individual was 50 for each dyad within the 4 OMUs. The indexes were groomed by another adult. 51

Table 2 Frequency of each behavior for each individual across the 4 OMU 1 2 Name Number of Sitting Sitting proximity Grooming Being groomed 3 scans alone To To To To By By dominant another dominant another dominant another 4 male female male female male female 5 6 females in LP’s OMU 6 7 LP 2480 952 1288 68 120 8 HG 2476 1120 120 888 16 33 4 65 9 PF 2484 621 228 1323 0 56 4 67 10 SK 2484 1417 204 643 36 12 20 27 11 TH 2472 819 236 1001 24 38 16 45 12 DM 2343 440 400 847 20 118 4 46 13 WM 2288 442 100 1226 24 75 20 82 14 5 females in JB’s OMU 15 JB 2960 1000 1564 167 149 16 YL 2944 1067 224 793 12 60 8 147 17 DBC 2932 1146 384 606 52 84 32 77 18 BD 3456 1280 700 844 44 126 88 59 19 XBC 3416 1965 164 727 24 112 20 100 20 YZM 2440 1266 92 504 17 59 19 58 21 22 5 females in BZT’s OMU 23 BZT 2716 1152 1232 152 164 24 BT 2916 1150 312 862 32 84 36 92 25 HTP 2960 1411 168 809 20 76 12 121 26 NZ 2832 1070 204 686 36 163 40 98 27 XC 3056 1794 188 678 20 70 24 78 28 YQ 2936 1169 360 835 56 63 40 67 29 4 females in RX’s OMU 30 RX 2780 600 1880 40 260 31 HX 2819 1558 506 396 50 34 10 146 32 BHX 2920 1712 340 648 60 77 10 0 33 JD 2800 1468 260 662 40 68 20 95 34 KK 2810 1426 370 754 104 106 0 44 35 36 In each one-male unit (OMU), the first individual is a resident male and other individuals are females. The number is frequency of 37 each behavior for each individual. 38 39 40 41 greater than 0 and less than 1, in which 0 represents 2 Social index among each dyad within the 4 one- 42 individuals that never socially interact with each other male units 43 in the phase and 1 represents 2 individuals dyad that al- 44 ways socially interact with each other in the phase. The proximity index, the grooming index, and the be- 45 ing groomed index represented the dyad relationship for Differences among each dyad on social activities 46 specific activity phases, but they did not represent all so- 47 Multivariate ANOVA was used to test the differences cial interactions among individual dyads. According to 48 among dyads within the OMUs based on the dyad stan- social time for each dyad, we used the rate of each ac- 49 dard indexes (proximity, grooming and being groomed). tivity’s social time as a weight factor and calculated the 50 51

1 different weights for each phase index and quantified and the RX unit (F = 0.814, df = 3, P = 0.053); however, 2 each dyad’s social interaction index as follows: significant differences did exist in the JB unit (F = 37.752, 3 Social indexAB = (‘a’ × proximity indexAB) + (‘b’ × df = 4, P = 0.000) and BZT unit (F = 5.780, df = 4, 4 grooming indexAB) + (‘c’ × being groomed indexAB) . P = 0.017). According to multiple comparisons, the rela- 5 tionship between DBC and JB (P = 0.000) and between Both A and B represent the individuals in each dyad; 6 BD and JB (P = 0.000) exhibited significant differenc- ‘a’ represents the rate of proximity in number of A and 7 B scans; ‘b’ represents the rate of grooming in num- es with other male–female dyads. The relationship be- 8 ber of A and B scans; and ‘c’ represents the rate of being tween YQ and BZT (P = 0.028) also showed significant 9 AB groomed in A and B scans. The proximity index , the differences with other male–female dyads. 10 AB AB grooming index and the being groomed index rep- 11 Relationship difference among female–female resent the activity phase index of dyad A and B. The so- 12 dyads across the 4 one-male units cial indexes were greater than 0 and less than 1, where 0 13 represents 2 individuals in a dyad that never socially in- Multivariate ANOVA results showed that the re- 14 teract with each other, the most distant relationship, and lationship among female dyads in the LP unit exhib- 15 1 represents 2 individuals that always socially interact ited no significant differences, as follows: female– 16 with each other, the most intimate relationship. HG (F = 1.709, df = 4, P = 0.240), female–PF (F = 3.074, 17 All statistical tests used in this study were performed df = 4, P = 0.083), female–SK (F = 0.595, df = 4, 18 using SPSS 11.5 (SPSS, Chicago). Tests were 2-tailed, P = 0.667), female–TH (F = 1.821, df = 4, P = 0.218), 19 with significance level set at 0.05. female–UK (F = 2.468, df = 4, P = 0.129) and female– 20 WM (F = 0.963, df = 4, P = 0.447). 21 22 RESULTS In JB unit, the relationship among female dyads 23 showed significant differences. However, female–YL (F = 4.284, df = 3, P = 0.061), female–DBC (F = 3.217, 24 Activities index for individual dyads within 4 df = 3, P = 0.104), and female–XBC (F = 4.031, df = 3, 25 one-male units in each activity phase P = 0.069) exhibited no significant differences, but sig- 26 nificant differences were observed for female–BD (F = 27 Based on 3 activity indexes, which are proximity in- 11.783, df = 3, P = 0.006) and female–YZM (F = 6.585, 28 dex, grooming index and being groomed index, the in- df = 3, P = 0.025). Multiple comparisons showed that 29 dividual dyad relationship show a sequence in each ac- among dyads of female–BD, the relationship between 30 tivity phase (see Table 3). For each activity phase, individual dyads had a sequence in their OMU that YL–BD and XBC–BD (P = 0.391) showed no signifi- 31 represented the tendency for 2 individuals to estab- cant differences, but significant differences were detect- 32 lish a relationship within such an activity phase; how- ed with DBC–BD (P = 0.011) and YZM–BD (P = 0.009). 33 ever, the sequences of individual dyads in 3 activi- For the relationship among dyads of female–YZM, 34 ty phases were different. Using LP–female index as YL–YZM had a significant difference with DBC–YZM 35 an example, in proximity phase, the LP–female rela- (0.008), BD–YZM (0.011) and XBC–YZM (0.016). 36 tionship tendency was UK–LP(0.32) > TH–LP(0.19), 37 In BZT unit, the relationship among female dyads SK–LP(0.19) > PF–LP(0.16) > HG–LP(0.10) > WM– 38 varied. While female–BT (F = 4.397, df = 3, P = 0.058), LP(0.08); in the grooming phase, the LP–female rela- 39 female–HTP (F = 4.080, df = 3, P = 0.068), female– tionship sequence was SK–LP(0.48) > TH–LP(0.31) > 40 NZ (F = 1.406, df = 3, P = 0.330) and female–XC (F = WM–LP(0.26) > HG–LP(0.17) > UK–LP(0.12) > PF– 41 3.461, df = 3, P = 0.091) had no significant differenc- LP(0.03); in the being groomed phase, the LP–female 42 es, differences did exist among dyads of female–YQ relationship sequence was SK–LP(0.34) > TH–LP(0.22) 43 (F = 12.618, df = 3, P = 0.005). Multiple comparisons > WM–LP(0.20) > UK–LP(0.14) > HG–LP(0.11) > PF– showed that the dyad of NZ–YQ had significant differ- 44 LP(0.02). ences with BT–YQ (0.009), HTP–YQ (0.002) and XC– 45 YQ (0.001). 46 Relationship differences among male–female In RX unit, no significant differences existed among 47 dyads within the 4 one-male units 48 female dyads, as follows: female–HST (F = 2.280, df = 49 The multivariate ANOVA test showed that for female 2, P = 0.218), female–RST (F = 0.314, df = 2, P = 0.747), 50 and the resident male dyads, there were no significant female–GT (F = 0.995, df = 2, P = 0.446) and female– 51 differences in the LP unit (F = 2.691, df = 4, P = 0.086) HM (F = 0.593, df = 2, P = 0.595).

Table 3 Proximity (P), grooming (G) and being groomed (BG) indexes for adult individual pairs within the 4 OMUs 1 2 LP’s OMU 3 HG PF SK TH UK WM 4 P G BG P G BG P G BG P G BG P G BG P G BG 5 LP 0.1 0.17 0.11 0.16 0.03 0.02 0.19 0.48 0.34 0.19 0.31 0.22 0.32 0.12 0.14 0.08 0.26 0.2 6 HG 0.2 0.23 0.17 0.06 0.08 0.07 0.21 0.12 0.1 0.22 0.07 0.11 0.08 0.27 0.23 7 8 PF 0.11 0.02 0.02 0.19 0.2 0.18 0.16 0.24 0.38 0.31 0.17 0.16 9 SK 0.09 0.08 0.08 0.1 0.08 0.14 0.23 0.04 0.04 10 TH 0.1 0.11 0.2 0.22 0.09 0.09 11 UK 0.11 0.29 0.45 12 JB’s OMU 13 14 YL DBC BD XBC YZM 15 P G BG P G BG P G BG P G BG P G BG 16 JB 0.17 0.08 0.07 0.3 0.28 0.33 0.45 0.39 0.45 0.13 0.15 0.16 0.09 0.15 0.16 17 YL 0.19 0.22 0.17 0.17 0.25 0.2 0.22 0.28 0.21 0.21 0.28 0.18 18 19 DBC 0.14 0.11 0.13 0.13 0.23 0.27 0.15 0.09 0.11 20 BD 0.25 0.21 0.24 0.13 0.11 0.13 21 XBC 0.11 0.13 0.14 22 BZT’s OMU 23 BT HTP NZ XC YQ 24 25 P G BG P G BG P G BG P G BG P G BG 26 BZT 0.26 0.25 0.23 0.15 0.13 0.11 0.19 0.22 0.25 0.18 0.18 0.17 0.3 0.63 0.35 27 BT 0.29 0.27 0.22 0.12 0.18 0.21 0.19 0.15 0.13 0.2 0.13 0.13 28 HTP 0.16 0.29 0.32 0.19 0.13 0.11 0.16 0.13 0.11 29 NZ 0.18 0.24 0.28 0.25 0.15 0.2 30 31 XC 0.16 0.11 0.11 32 RX’s OMU 33 HX BHX JD KK 34 P G BG P G BG P G BG P G BG 35 36 RX 0.57 0.48 0.14 0.24 0.4 0.26 0.19 0.41 0.16 0.25 0.43 0.36 37 HX 0.08 0.17 0.23 0.14 0.39 0.27 0.12 0.23 0.34 38 BHX 0.23 0.09 0.18 0.31 0.05 0.3 39 JD 0.27 0.2 0.42 40 LP, JB, BZT and RX are resident males and other individuals are females in their one-male unit (OMU). The numbers represent the 41 activities index for each individual pair in each activity phase. 42 43 44 45 Social index for each dyad across 4 one-male ads. Thus, the social index was quantified as shown in 46 units Table 4 and Fig. 1. 47 48 In regards to the social index, the BD–JB, DBC–JB Statistical analysis showed that social relationship di- 49 and YQ–BZT social indexes were 0.45, 0.30 and 0.32, versity existed within the OMUs; however, these results 50 respectively, which were greater than other female–male did not show the interaction tendency of individual dy- 51

1 Table 4 Social index for each pair across the 4 OMUs and XBC–BD (0.25) were greater than the relationships 2 Social index for LP’s OMU in DBC–BD (0.14) and YZM–BD (0.13). This was ob- 3 HG PF SK TH UK WM served for YL–YZM (0.21) in JB unit and NZ–YQ (0.24) 4 LP 0.11 0.16 0.21 0.19 0.31 0.10 in BZT unit, in which the social indexes were all great- 5 HG 0.20 0.06 0.20 0.22 0.11 er than for other female dyads in their OMUs. Although 6 4 females in 2 OMUs built good relationships with each PF 0.11 0.19 0.17 0.31 7 other, based on the social indexes for the other female SK 0.09 0.10 0.23 8 dyads in the 4 OMUs, our results indicate that female 9 TH 0.11 0.22 golden monkeys had no significant tendency to build re- 10 UK 0.16 lationships with each other. 11 Social index for JB’s OMU 12 YL DBC BD XBC YZM DISCUSSION 13 JB 0.17 0.30 0.45 0.14 0.10 14 YL 0.19 0.18 0.23 0.21 In nonhuman primate societies, individual animals 15 DBC 0.14 0.15 0.14 within a social group are not distributed randomly and 16 BD 0.25 0.13 spatial proximity is commonly associated with inter-in- 17 XBC 0.12 dividual competition for limited resources (Matsumura 18 Social index for BZT’s OMU & Okamoto 1997). In this study, based on the proximi- 19 BT HTP NZ XC YQ ty and grooming data within 4 golden snub-nosed mon- 20 BZT 0.26 0.15 0.20 0.18 0.32 key OMUs, we test the relationship diversity for them. 21 BT 0.29 0.14 0.19 0.19 We found that the individual relationships in snub-nosed 22 HTP 0.19 0.18 0.16 monkey were dissimilar to those of other primates, for 23 NZ 0.19 0.24 all adult females had a tendency to socially interact with 24 the resident male within their OMU, although most ex- XC 0.15 25 hibited no significant differences. Adult females have Social index for RX’s OMU 26 the inclination to interact with each other generally but 27 HX BHX JD KK the social bonding tendency is very weak. In the pres- 28 RX 0.56 0.24 0.19 0.26 ent study, 3 social relationship characteristics in Qinling 29 HX 0.11 0.17 0.16 snub-nosed monkeys are summarized. 30 BHX 0.23 0.31 Adult females showed a very weak social relationship 31 JD 0.28 with the resident male within OMUs. In each of the ac- 32 Note: LP, JB, BZT and RX are resident males and other indi- tivity phases of this study, females showed high rates of 33 viduals are females in their one-male unit (OMU). The num- social interaction with other females and low rates with 34 bers represent the social index for each individual pair in each 35 OMU. their resident male within their OMU and resident males 36 appeared socially on the periphery in the study OMUs 37 (Table 2, Fig. 1). Previous studies suggested that males 38 ordinarily left their natal OMU before reaching sexual 39 maturity and replace the adult OMU resident male when dyad social indexes in their OMUs. Although 3 adult fe- 40 they reach sexual maturity (Ren et al. 2000; Zhang et males in 2 OMUs exhibited a tendency to build rela- 41 al. 2006). Thus, resident males depend on sexual attrac- tionships with the male, most females did not exhibit 42 tion to stay within the OMU (Bachmannand & Kum- a significant tendency to build a relationship with their 43 mer 1980), which indicates that females play an impor- resident male. 44 tant role in OMU cohesion and allow the resident male The same situation existed in female–female inter- 45 stay in an OMU by sexual choice. Therefore, in regards action across all 4 OMUs. The female dyad relation- 46 to female attitudes to the resident male, social interac- ships within LP unit and RX unit exhibited no signifi- 47 tion between male and female golden snub-nosed mon- 48 cant differences, while female dyad relationships within keys showed a tendency towards social interaction but 49 JB unit and BZT unit did exhibit significant differenc- no significant differences were observed among females 50 es. In relation to the social index for JB unit among dy- within the OMU. 51 ads of females–BD, the relationships in YL–BD (0.18)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Figure 1 Sketch map of relationship among adult individual pairs for 4 one-male units (OMUs). Based on the social index, each 29 adult individual pair relationship is printed in the sketch map. The 4 boxes represent 4 resident males, and the 20 circles represent 30 20 adult females in 4 OMUs. The lines among individuals represent the relationship between 2 individuals. The thickness of the 31 lines represents the social index between adult individual pairs. 32 33 34 Relationships among adult females within each OMU low relationships with intergroup competition and natal 35 were not strict and maternal, but very loose. In this females build kinship to intergroup competition; howev- 36 study, when females wanted social interaction with other, this resulted in there being no significant differences 37 ers, they chose females within OMU most of the time; in social interaction among the observed females. 38 however, which target female was chosen varied (see Social relationships in snub-nosed monkeys showed 39 Tables 3 and 4). According to group demographic data a different pattern from the known results in gelada 40 which we collected, 2 patterns of tendency exist among and hamadryas baboons. Both baboons and the gold- 41 females when they choose partners for social interac- en snub-nosed monkey have similar multi-level social 42 tion. Kinship existed in the dyad between a mother and structures (Kummer 1968; Mori 1979a,b; Kawai et al. 43 her offspring (such as YL–XBC relationship in JB unit) 1983; Zhang et al. 2006; Qi et al. 2009, 2010). In gela- 44 and fellow relationships existed in the dyad between fe- da baboon, the strict kinship among females is the pri- 45 males who immigrated together from outside into the mary factor in keeping the OMU stable and only 1 adult 46 OMU (such as the HX–BHX relationship in RX unit). alpha female builds a strong relationship with the res- 47 Because golden snub-nosed monkey individuals within ident male, while the other females build relationships 48 OMU need get benefits and reduce individual competi- with each other (Dunbar 1983a). However, in hamadry- 49 tion due to limited resources, migrant females build fel- as baboons, female mate choice is the main factor in 50 51

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