We monitored a group of 53 stump-tailed macaques from dawn to dusk, during 1998-2000 in the Hollongapar Gibbon Sanctuary, Assam, India to understand socio-ecological behaviour. We focused on identifying the lodging tree species used by stump-tailed macaques. During 1504 hours of observation, we recorded that the stump-tailed macaque group used six tree species for their lodging.Artocarpus chamawas the most selected (preferred) species (45%) followed byFicus bengalensis(35%),Castopnopsis indica(8%),Ficus religiosa(7%),Mangifera sylvatia(3%) andFicus benjamina(2%). The average diameter at breast height of the lodging trees ranged from 0.68 to 2.4 meters and the height ranged from 20 to 35 meters. We further observed that in 85% cases stump-tailed macaques used one lodging site for one night only while 15% of their sleeping was in the same lodging tree for two consecutive nights. The study also revealed that the strong selectivity for preferred lodging sites is influenced by factors including group foraging strategies, predator avoidance and social accommodation. Above all the preference and selectivity for lodging sites is found to be critical from conservation perspective of the species.
Lodging tree,Macaca arctoides, Seasonal variation, Hollongapar, Assam, India.
Sleeping site is an integral component of primate ecology. Primates use diverse sleeping sites. According to Andersosn (1984) half of the lives of primates are spend on their sleeping sites. Therefore, selection of suitable sleeping sites is very crucial for the survival of individual of any primate species.
The lodging tree selection has been reported in pigtailed macaque (Caldecott,1986; Albertet al2011), Assamese macaques (Sarkar, 2002) bonnet macaques (Rahaman & Parthasarathy 1969; Ramakrishna and Coss), golden langurs (Biwas, 2004, Chetryet al.,2002; Chetry & Chetry, 2009), hoolock gibbon ( Das, 2003; Chetryet al., 2016), black crested gibbon (Fan and Jiang, 2008), pileated gibbons (Phoonjampaet al., 2010), Skywalker gibbon ( Feiet al,……. ) golden-handed tamarin (Day & Elwood 1999), Proboscis monkeys (Bernardet al., 2011) and François’ langur (Zhouet al., 2009).
Stump-tailed macaque is one of the least studied species in wild. Only few studies have been attempted on stump-tailed macaque in natural habitats (Chetry & Mohnot 2000; Chetry & Bhatacharjee, 2002; Chetryet al., 2003; Chetry, 2004; Chetryet al, 2007). A detailed account of selection of lodging sites by this species is lacking except for a preliminary report by Chetry & Bhattacharjee (2004). The aim of present study is to highlight the diversity of lodging trees of a wild group of stump-tailed macaque in the Gibbon wildlife sanctuary. The study also discusses about the socio-ecological factors influencing the selection of lodging sites by stump-tailed macaque.
The study site, the Hollongapar Gibbon Sanctuary, Jorhat, Assam, North-east India covers an area of 2,098 hectares. Located at 26°45`N and 94°25`E, its altitude ranges from 100-120 msl. Before the name of this Sanctuary (GWLS), came into existence on 30th July, 1997, it was known as Hollongapar Reserve Forest. The Sanctuary is characterized by a lowland forest with numerous small streams. It is surrounded by human habitations and tea gardens making it a “forest island”. The annual rainfall during the study period was 1870.5 mm and the average minimum and maximum temperatures were 20.15°C and 28.75°C respectively.
The major forest type in the sanctuary is tropical moist deciduous dipterocarpus forest. The principal trees, which form the top canopy, areDipterocarpus retusus, Sapium baccatum, Arctocarpus chama, Largerstroemia floreginae, Canarium resiniferum, Castopnopsis indica, Anthocephalus cadamba, Amoora wallichi, Duabanga sonneratioides,andMansonia dipikae. The middle storey is generally composed ofVatica lancefolia, Mesua ferrea, Dilena indica, Aqualaria agolacha, Biscofia Mangifera javanica, Ficus glomeruta, Elaeocarpus ganitrus.The lower storey is composed of three bamboo species viz.Pseudostachym polymorphum, Bambusa pallida and Calamusspecies. The undergrowth consists of species likeClerodendron, Eupatorium, Mikenia scandews and Commelina, etc
One group of 53 stump-tailed macaques was selected for the study. The group was composed of ten adult males, one sub-adult male, 15 adult females, eight juvenile females, ten juvenile males and nine infants. Apart from the stump-tailed macaque, 6 other primate species such asHoolock hoolock,Trachypitheucs pileatus, Macaca leonina, Macaca assamensis,Macaca mulattaandNyctcebus bengalensiswere found in the study area (Chetryet al., 2001).
After pooling the data from 1504 hours of observation, the following results were obtained.
A total of 75 lodging trees were recorded in the home range of the study group during the study period of 98 night halts.
The stump-tailed macaques selected only large, tall and emergent trees for night sleeping. All the lodging trees were on average 20m in height and 1.5m DBH (Table 1). The majority of the trees selected for lodging supported vines, lianas and small regenerating trees.
Stump-tailed macaques showed strong selectivity in choosing their lodging sites. From 85 species of trees in their home range, the group selected only 6 tree species for sleeping during night. Out of these 6 species (Table 1), they are found to roost mostly upon 2 species namelyArctocarpus chama(45%) andFicus bengalensis(35%). Therefore, we state them preferred species.
Marked seasonal variations were also recorded in the selection of lodging sites (Table 1). The stump-tailed macaques used to lodge inArctocarpus chamaandFicus bengalensisin all the four seasons. However, during monsoon season they preferred to lodge inFicus bengalensis(62%), whilein retreating monsoon, preference was high forArctocarpus chama( 50%).
The stump-tailed macaque group used 75 trees of 6 different species belonging to 4 families for lodging. Interestingly, all these trees were food trees of the stump-tailed macaques and they procured different food items viz. fruit, seed, leaf, flower etc., from these plants in different seasons. However, they never used these trees during the fruiting stage as lodging sites. This is likely to be a strategy of avoiding disturbances from nocturnal frugivores like bats and slow lorises. Daset al.,2005 reported similar kind of avoidance in using fruiting food plants as sleeping sites by Hoolock gibbon. The use of only six species of trees clearly shows that stump-tailed macaques are very selective in choosing their lodging sites. Species like golden langur, Hoolock gibbon, Proboscis monkey, Skywalker gibbon also show strong selectivity in choosing lodging trees (Biswas, 2004; Das, 2003; Feiet al.,2017). Seasonal variation in using the lodging sites was also observed, as the group preferred different species of trees in different seasons. As far as using pattern of sleeping trees go in 85% of the cases, the macaques were seen not to lodge in the same tree for two consecutive nights. Rather they returned to a lodging tree after an interval of 2-8 days. This cyclic return of the group to a particular lodging tree can be best described through their foraging behaviour. Each day they start their travel from the previous night’s lodging tree. As they do not forage within the same patch every day, they do not return to the previous lodging tree the next day but instead lodge in a different tree every night. In this manner, they change their lodging sites according to their daily foraging habit. However, after a few days (2-8) they return to the same tree. Thus the study clearly shows the influence of foraging behaviour on the frequency of using the sleeping sites in stump-tailed macaque. Several studies have established the effect of foraging on sleeping site selection and other sleeping-related behaviour in primates (Chapman 1989; Von Hippel 1998; Teichroebet al.,2012). Moreover, changing sleeping tree in every night by the study group of stump-tailed macaque in majority cases also appears as an alternative strategy of reducing predation risk. Feiet al.,(2017) observed that the sky walker gibbons rarely reused sleeping trees in consecutive nights. Similar results have been found for a number of primate species including pileated gibbon (Hrdy, 1977; Reichard, 1998; Smithet al., 2007) , black-crested and white-handed gibbons [Fan & Jiang, 2008; Reichard, 1998) and Proboscis monkey ( Bernardet al.,2011). In contrast, Ramakantha & Coss (2001) observed a bonnet macaque troop using the same sleeping tree every night. Likewise reuse of sleeping trees for consecutive nights is a norms in some capuchin monkeys (Di Bitettiet al., 2000), and Kloss’s gibbons (Tenaza & Tilson, 1985). According to (Caineet al.1992; Liu and Zhao 2004) predators pose a major threat to primates when they are asleep. Our results have also shown that stump-tailed macaques invariably uses only tall lodging trees for night sleeping. This inherent habit of selecting tall trees as sleeping sites suggests that it is another anti-predation strategy of stump-tailed macaque. By adopting this strategy they actually try to avoid land predators in the habitat as predators cannot access top level of lofty and bulky trees easily. Chetryet al(2003) identified clouded leopard (Neofelis nebulosa), leopard (Panthera pardus) as potential predators of stump-tailed macaque in the study site. Anti-depredation behaviour has already been well identified as a prime determining factor for sleeping related behaviour in primates (Barnettet al., 2012; Di Bitettiet al.,2000; Duarte and Young 2011; Smithet al. 2007; VonHippel 1998; Zhouet al. 2009). Selection of tall trees for sleeping is widespread in different primate species as a primary means of anti-predation (Cuiet al., Liu and Zhao 2004; Ramakantha & Coss (2001); Bernardet al., 2011; Phoonjampaet al., 2010; Feiet al.,2017).
The study also shows that majority of the trees selected by study group of stump-tailed macaque were entangled with vines and lianas. It is likely that they used the tangled vegetation as a hiding cover to avoid detection by predators. However, occurrence of some potential predators like snake in the cover of vines cannot be overruled. In contrast to stump-tailed macaque the preference for tall trees without vines and lianas is exhibited by Pileated gibbons (Phoonjampaet al.,2010 ) Kloss gibbon (Tenaza & Tilson, 1985) and Skywalker gibbons( Feiet al., 2017).
Our results further reveal that all the 53 members of the study group slept in a single tree rather than scattering in sub groups in different trees at night. This might have been another important reason that stump-tailed macaques always selected tall emergent trees with profuse branching which can provide the necessary accommodation for the entire group. Sleeping tree architecture is also important in some arboreal primate species (Rasoloharijaonaet al., 2008). It has been observed that the physical structure of a tree is an important factor in the choice of night sleeping trees in proboscis monkeys (Bernardet al., 2011). By allotting accommodation to all the group members large trees may facilitate social interaction, group cohesion, and communication (Anderson 1998; Di Bitettiet al.,2000).
In a nutshell, it can be said that predator avoidance is one of the most vital factor that influences lodging tree selection in stump-tailed macaque like in many other species of primate. Additionally, group foraging strategy and social accommodation also play key roles in sleeping tree selection of stump-tailed macaque. This high selectivity for lodging sites definitely bears strong conservation implications. Because of this strong selectivity for lodging trees the populations of stump-tailed macaque in fragmented habitats may become more susceptible to predation in absence of suitable lodging trees and which may in the long run affects the population size. Habitat destruction with indiscriminate removal of suitable lodging trees may become a crucial detrimental factor for the species. Therefore, the study emphasizes on systematic identification and conservation of lodging trees of stump-tailed macaque in different habitats as a part of its long term conservation.
Our thanks go to colleagues from the Forest Department of Assam, especially the Jorhat Division for providing us permission to work and logistic support during the fieldwork. We are thankful toProf. S. M. MohnotandDr. Arun Srivastavaof Indo-US Primate Project for helping in designing the project. We are thankful toMr. Deban Borah,late Noren Bhuyan, Jibon Borah and Mr. B. B. Gurungand his family who assisted in the fieldwork, without whose support this work would not have been possible. A special thank goes to lateDr. Robert Horwich, for going through the manuscript with valuable suggestions. This research is a part of cooperative programme of the Ministry of Environment and Forests Govt. of India and the US Fish and Wildlife Service (Grant Agreements No.INT/FWS-22).
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