An ear-piercing shrill! We stop dead in our tracks and listen. ‘Just a bird’, I mutter and walk on. Silence. Thud! Some commotion in the nearby bamboo patch. ‘Could it be an elephant?’ we wonder. More silence. Another thud follows a shriller cry! We look at each other. We can’t be wrong this time. It must be them. Quickly positioning ourselves on the ground we wait with bated breath. After a few restless minutes, a head with its red mottled face finally emerges out from the thick undergrowth. It looks suspiciously on both sides of the clearing, fixes its eyes on us for a moment and quickly disappears. Soon the entire group marches in front of us and vanish on the other side. Ending a desperate seven day-long search, we finally have our sights on an elusive primate species in this isolated and fragmented forest patch.
I have been studying the behavioural ecology of the stump-tailed macaque Macaca arctoides in the Hollongapar Gibbon Wildlife Sanctuary in Assam for the last three years. The sanctuary is a 21-square kilometre tropical lowland, semi-evergreen rainforest patch close to the foothills of Nagaland, surrounded by tea gardens, agricultural fields and human settlements. This particular study is a sub-set of broader research objectives including the behavioural ecology of other primate species of the sanctuary. I am trying to understand how a community of primates, particularly the three species of macaques — the stump-tailed , pig-tailed macaque Macaca leonina, and rhesus macaque Macaca mulatta — co-exist together in a fragment with diminishing resources.
In the mist-wrapped quilt of darkness, my motorbike feels intrusive at 0400 hrs on the road that leads to the entrance of the park. Setting off from Bheleuguri village, my temporary home, my field assistants and I often negotiate our way between herds of wild elephants to reach the macaques’ sleeping tree before they descend from their roosting site and vanish into the thick undergrowth. It was a frantic seven-day search before we finally sighted them, and we simply couldn’t afford to lose them. On arrival, the sight of cuddling lumps of black bodies on the distant branches of the Ficus tree brings a great sense of relief. I prepare to follow the group from dawn to dusk for next five days unless we lose them, and then switch to observing the other primates of the sanctuary for the rest of the month.
Gigantic Ficus trees, with their sprawling canopies, are the most preferred sleeping trees although they equally prefer trees such as Dipterocarpus macrocarpus, Artocarpus chama and Castonopsis indica. These sleeping sites are distributed throughout their home ranges, including areas where they overlap with a neighbouring troop. The tall trees ensure safety from leopards Panthera pardus and pythons Python molurus—the primary predators of macaques in the sanctuary. Unlike other primates of the sanctuary and those individuals of their group that prefer to sleep on different trees, the entire group of stump-tailed macaques shares a single roosting tree. The majority of sleeping sites and trees are selected repeatedly by the group.
As the first rays of sunlight kiss the canopy high above, the group stirs slowly and is ready to start a new day. They go about their morning rituals with fresh showers of urine and faeces adding pungency to the air, already thickened by the odour of their droppings. With us intruding into their ablutions, it’s no big deal if an unwelcome lump of droppings occasionally land on our heads!
Their interaction in the morning is dominated by allogrooming activities, while the group is still on their sleeping tree. Grooming helps in maintaining social bonds besides facilitating the removal of ectoparasites from one another’s bodies. Being a terrestrial primate, they accumulate heavy loads of ectoparasites while foraging in the undergrowth, especially bamboo thickets. Although occasionally displayed while foraging, much of their allogrooming is almost exclusively confined to mornings and evenings on their sleeping trees.
All of a sudden, a fierce fight breaks out amongst the adults and the group starts moving down the sleeping tree. The fragment of rainforest wakes up once again with shrills shrieks of aggression among the adults. Generally, adult males descend using trunks of trees, while juveniles use numerous lianas for their descent. But today, all of them descend using a single thick liana. A perfect time to enumerate the group! Knowing exactly what to do under these conditions and remembering their field-training, Dilip and Noren, my local assistants, start counting each individual descending the tree and I begin to assign age and sex to each of them. Finally, when all the individuals are on the ground, we match our data. It stands to 133!
This group, to the best of my knowledge, is the largest reported group of stump-tailed macaque anywhere in the world. Looking at their sex ratio, it becomes evident that the recruitment rate of the group is extremely high. The number of juveniles and infants is twice the number of adult females. This means that the females are breeding every year! Moreover, the size of the two troops that the sanctuary harbours has doubled since 1998. This is quite incredible! How do we explain the existence of such a large group? A larger group size perhaps improves their access to resources. Given the finding that higher population densities are found within the sanctuary, the species has probably benefited from the protection it receives in the sanctuary. The lack of space to form a new group could also be a plausible reason why a single group has grown so large.
I plough through rain-fed streams as I follow the group, as they hurriedly cross overhead through the dense canopy. Today’s destination is an area with huge trees of Artocarpus chama. The party splits into three recognisable sub-groups, and each of them position themselves separately in three different trees; a few of them start feeding on fruits fallen to the ground.
Artocarpus chama is an important food resource for the primate species in the sanctuary. Besides them, squirrels, deer and elephants have also been seen to feed on them. Elephants, in fact, help dispersing this species, as one can see numerous saplings emerging out from their dung, away from the parent trees. The convergence of species to resources when found in plenty and switching to a different set of resources during lean periods is one of the many mechanisms by which different species live together even under conditions of limited resources and reduce inter-species competition. A greater overlap in food resources indicates that two species would compete for the same resources when it is in shortage and during this tussle, the out-competed species could eventually disappear. This might be one of the several explanations for the disappearance of many primate species from the fragmented forests of upper Assam, where primates compete with each other for resources that are diminishing rapidly.
After a bounteous early lunch, with cheek pouches stuffed with these juicy offerings of a fruiting tree, the group moves ahead but abruptly turns back, immediately moving in the opposite direction. A few minutes later, a train pierces the quiet woods with an extended shriek. The group has finally hit the dead end of the park, both literally and metaphorically!
The sanctuary is divided into two unequal chunks of forests by a railway track and this is one of its most serious conservation concerns. During my study period, I have seen three capped langurs, two pythons, and several other animals that met their ends on this track. The rate at which these animals are being mowed down is alarming as this will not only impact the dwindling numbers of several solitary species but also have its impact on changing the group composition in social species like primates. The idea of connecting these patches through canopy bridges has been mooted, but not materialised yet. Besides, it is unlikely that it can help terrestrial species like stump-tailed macaques and have, in fact, never been seen doing so in the entire study period.
The group has already moved a considerable distance from its sleeping tree and found a log, laden with mushrooms – an unexpected delicacy. Within moments, the log is disrobed of its fungal ornamentation. A pig-tailed macaque, feeding quietly high above on a Dillenia tree, watches this marauding army for a while, displays its typical puckered face and resumes its feeding bout as if nothing has ever happened!
Stump-tailed macaques generally avoid interactions with other primate species but whenever they do, they seldom indulge in aggressive interactions. Unlike their South American cousins, primates in this part of the world do not form poly-species association — a temporary association between two or more species that usually form to enhance foraging efficiency and predator avoidance, however, such associations never seem to develop in the tropical forests of northeastern India. Although Hollongapar is reported to harbour seven species of primates, the existence of at least one species—the Assamese macaque, and its single population—is, today, doubtful. I have not seen this population since 2005. Has this species become locally extinct in this threatened fragment? If yes, could we attribute its disappearance to inter-specific competition with the other sympatric primate species of the sanctuary?
The group trudges through the opening of a bamboo thicket and we find that a female is actually leading the party today. We wait till all individuals follow her and soon we too join the caravan.
Do stump-tailed macaques have spatial memory of the forest? Researchers are still unable to understand how primates process spatial information mentally to navigate in their natural environment. Nevertheless, if the ranging behaviour of stump-tailed macaques is any indication, they definitely seem to possess some kind of map of the forest in their mind. I am intrigued by the way they find their select sleeping trees and trees laden with ripe fruits in these dense forests where visibility is extremely poor.
It is time to climb up the roost once again before the darkness thickens in the forest. The entire group ascends to the topmost branches and position themselves – grooming, huddling, displacing one from a favourite spot and activities ‘social’ to macaques beyond foraging and feeding unfold. The group unrecognisable beyond the individual silhouettes becomes inaccessible to me. I look at the last individual who still struggles to find a suitable place to rest. Tomorrow, I will come back before they wake up and see how they unfold their secret of life in front of me. For now, I have to make a long winding tour back to my own sleeping site!
The macaques seem to be doing fairly well in Hollongapar, at least for the time being, given their healthy breeding population. But how long this population will survive in the long run is anybody’s guess, as sooner or later the sanctuary will reach its maximum carrying capacity.
In other northeastern states the status of the stump-tailed macaque is still unknown but all over the hills, they are hunted for their meat. In the Garo and Khasi Hills of Meghalaya as well as in the Ngenpui Wildlife Sanctuary and Dampa Tiger Reserve of Mizoram, they often raid jhum fields. In fact, in Nagaland, they were considered a serious pest, as reflected in the writings of McCann in 1933. He observed that these monkeys were troublesome to Naga cultivators and did considerable damage to their crops as did the rhesus macaques in the plains. He further added that the Nagas were somewhat apprehensive of them on account of their aggressive display and ability to attack a lone man or woman. Today, however, the species must be threatened in this state as most Naga tribes are known for their hunting skills.
In the upper Brahmaputra valley, the most endangered primate species are found in reserve forests that are outside the Protected Area (PA) network. Although legally protected to some extent, they have for long been ignored and so have their unique species assemblages. An integrated landscape-level approach leading to conservation planning is urgently needed. But, ultimately, the involvement of local people in this endeavour will determine the success of any possible conservation intervention.
I am heading back to the camp, after a five-day schedule with the stump-tailed macaques. It is getting dark and I am not able to see anything beyond us. Beside me I can see the happy faces of Noren and Dilip da, exhausted but excited, their passion and enthusiasm unmatched, their spirit unparalleled. Much later they reveal that they don’t like anything in life as much as working in these forests, and given a chance, they are ready to leave the luxury and comfort of their homes as well. ‘Bhal lage’, (‘feel good’) – this is their invariable, gentle answer when asked why they want to do this work. Even I feel happy, as those two words seem to echo the passion for conservation that we must evoke to ensure the future of the sanctuary as well as of the last stump-tailed macaques huddling in their roost as evening darkens around them.
An edited version of the article was published in the Sanctuary Asia, www.sanctuaryasia.com in October, 2011