Primates in fragments

Behavioural ecology of primates in the Upper Brahmaputra Valley of Assam

Over the last two centuries, the forests of Upper Brahmaputra Valley has been cleared for agriculture, human settlements timber extractions leading to a  landscape dotted with remnant lowland rain forests fragments of different sizes. We study how primates are coping to such heavy fragmentation of their habitats

  • A male stumptailed macaque Macaca arctoides

  • Western hoolock gibbon Hoolock hoolock

  • Stumptailed macaque infant

How green was the Valley?

All landscapes has their own histories and  in a noted historian’s words, “inquiry into their past can help us to learn how we came to this turn in the road and, what options lie ahead.” Historical deforestation had shaped the landscape of Upper Brahmaputra Valley. In this project we analysed the historical drivers of forest loss and habitat fragmentation in Upper Brahmaputra landscape over the last 15 centuries. The forest cover changes during the precolonial (before 1826), colonial (1826—1947) and the postcolonial (post 1947) periods were located within the political economy and demographic milieu of each regime. Our analysis showed that the Upper Assam landscape has shaped by the interplay of deforestation and natural reforestation which was strongly linked to the socio-political factors. In the current context of rising populations linked to immigration from neighbouring regions, dwindling share of agriculture in the state’s gross domestic product, and recent incentives to small tea growers in risk-prone agricultural landscapes, serious challenges remain to securing forests in this region

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Google Earth view of Upper Brahmaputra Valley

Coping with forest fragmentation

Having looking at the historical analysis of how various socio-economic factors led to forest loss and fragmentation in the Upper Brahmaputra Valley, we then examined how forest fragmentation, in turn, has affected primates in Upper Brahmaputra Valley (UBV).  We investigated the distribution of primate species in 42 habitat fragments of UBV. We particularly examined the role of ecological and anthropogenic factors at the local and landscape scale in shaping patterns of primate species richness, individual primate species distribution and local extinctions across habitat fragments. We explored how patterns of primate species richness and composition vary across fragments temporally and spatially. We found a persistence of several primate species of primates in these fragments even after being isolated for over a century. Various ecological, landscape and anthropogenic factors were influenced the occurrence and extinction of species in these fragments. 

Coping

Fragmented living: A hoolock gibbon in a fragment

Going, going, gone!

We analyse recent temporal trends in primate populations of four forest fragments of UBV using multi-year census data spanning 16 years.  We report the recent history and current status of six diurnal primates in one large (2,098 ha) and three small (< 500 ha) fragments of the Upper Brahmaputra Valley. I censused primates in the small fragments during 2002, 2005, 2009, in the large fragment in 2008, and used other published census data to derive population trends. We used key informant surveys to obtain historical occurrence data for these populations. Our analyses reveal the recent extinction of some populations and the simultaneous long-term persistence of others in these fragments over 16 years. Most populations appeared to have declined in the small fragments but primate abundance has increased significantly in the largest fragment over the last decade. Addressing the biomass needs of the local human populations, which appears to drive habitat degradation, and better protection of these forests, will be crucial in ensuring the future survival of this diverse and unique primate assemblage in the last rainforest fragments of the human- dominated Upper Brahmaputra Valley.

Divide and thrive, unite and perish

How closely related species co-exist, especially under conditions of resource limitation remains an intriguing problem in ecology. Having to share space and resources, such species are expected to have evolved a variety of behavioural mechanisms to reduce competition. Understanding such adaptation could also provide clues to design effective conservation strategies for these species.  The project examined the niche partitioning and co-existence of three congeneric species, the rhesus macaque, pig-tailed macaque and stump-tailed macaque, in  Hollongapar-Gibbon Wildlife Sanctuary, which still harbours a significant proportion of original species pool. An intensive observational study was conducted on two troops each of the three species over a period of 23 months from March 2008 to January 2010. We examined niche partitioning among the macaques along two major axes—space and food. Our results found significant interspecific differences among macaques in their utilisation of both horizontal and vertical space, as well as in their utilisation of food resources. The differential utilisation of space and food has enabled continued co-existence of the three macaque species in this fragment. At the fragment-level and over proximate time-scales, our results explain why primates, particularly the three species of macaques, are able to thrive even after being isolated for over one hundred years. 

People

Funding

Publications

  • Journal Article
    2014
    Local and Landscape Correlates of Primate Distribution and Extinction in Upper Brahmaputra Valley
    Conservation Biology 28(1): 95-106
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    PDF, 807 KB

    Habitat fragmentation affects species distribution and abundance, and drives extinctions. Es- calated tropical deforestation and fragmentation have confined many species populations to habitat rem- nants. How worthwhile is it to invest scarce resources in conserving habitat remnants within densely settled production landscapes? Are these fragments fated to lose species anyway? If not, do other ecologi- cal, anthropogenic, and species-related factors mitigate the effect of fragmentation and offer conservation opportunities? We evaluated, using generalized linear models in an information-theoretic framework, the effect of local- and landscape-scale factors on the richness, abundance, distribution, and local extinction of 6 primate species in 42 lowland tropical rainforest fragments of the Upper Brahmaputra Valley, northeastern India. On average, the forest fragments lost at least one species in the last 30 years but retained half their original species complement. Species richness declined as proportion of habitat lost increased but was not significantly affected by fragment size and isolation. The occurrence of western hoolock gibbon (Hoolock hoolock) and capped langur (Trachypithecus pileatus) in fragments was inversely related to their isolation and loss of habitat, respectively. Fragment area determined stump-tailed (Macaca arctoides) and northern pig-tailed macaque occurrence (Macaca leonina). Assamese macaque (Macaca assamensis) distribution was affected negatively by illegal tree felling, and rhesus macaque (Macaca mulatta) abundance increased as habitat heterogeneity increased. Primate extinction in a fragment was primarily governed by the extent of divergence in its food tree species richness from that in contiguous forests. We suggest the conservation value of these fragments is high because collectively they retained the entire original species pool and individually retained half of it, even a century after fragmentation. Given the extensive habitat and species loss, however, these fragments urgently require protection and active ecological restoration to sustain this rich primate assemblage.

  • Journal Article
    2012
    Trends in extinction and persistence of diurnal primates in Upper Brahmaputra Valley
    Oryx 46(2): 308-311
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    PDF, 345 KB

    The historical deforestation of the Upper Brahmaputra Valley in the Indian state of Assam has resulted in the transformation of its once-contiguous lowland rainforests into many isolated forest fragments that are still rich in species, including primates. We report the recent history and current status of six diurnal primates in one large (2,098 ha) and three small (, 500 ha) fragments of the Upper Brahmaputra Valley. We censused primates in the small fragments during 2002, 2005, 2009, in the large fragment in 2008, and used other published census data to derive population trends. We also used key informant surveys to obtain historical occurrence data for these populations. Our analyses reveal the recent extinction of some populations and the simultaneous long-term persist- ence of others in these fragments over 16 years. Most populations appeared to have declined in the small fragments but primate abundance has increased signific- antly in the largest fragment over the last decade. Addressing the biomass needs of the local human populations, which appears to drive habitat degradation, and better protection of these forests, will be crucial in ensuring the future survival of this diverse and unique primate assemblage in the last rainforest fragments of the human-dominated Upper Brahmaputra Valley.

  • Thesis
    2012
    Primate on the edge: Ecology and Conservation of Primate Assemblages in the Fragmented Lowland Rainforests of the Upper Brahmaputra Valley, Northeastern India
    PhD Thesis submitted to Manipal University, Manipal, Karnataka
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    PDF, 8.48 MB

  • Journal Article
    2012
    Socio-economic drivers of Forest Cover Change in Assam: A Historical Perspective
    Economic and Political Weekly 47(5): 64-72
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    PDF, 721 KB

    This article analyses the historical context of forest cover change in the upper Brahmaputra Valley of Assam during the precolonial, colonial and the postcolonial periods, locating these changes within the political economy and demographic milieu of each regime.In the current context of rising populations linked to immigration from neighbouring regions, dwindling share of agriculture in the state’s gross domestic product, and recent incentives to small tea growers in risk-prone agricultural landscapes, serious challenges remain to securing forests in this region. Empowering local communities and institutions, understanding tea plantation dynamics and managing the causes and consequences of recent demographic change are crucial to the conservation of forests there.

  • Popular Article
    2011
    Over one hundred years of solitude
    Zoo’s Print 26 : 5-8
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    PDF, 1.67 MB

  • Popular Article
    2011
    A remnant tale
    Sanctuary Asia 31 (5):42-47
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    PDF, 1.1 MB

    Natural history of the stump-tailed macaque, one of India’s least- known primates that is holding on for dear life in Assam’s tiny but rich Hollongapar Gibbon Wildlife Sanctuary.

  • Popular Article
    2010
    Monkey Watcher’s Diary
    Sanctuary Asia 30(5):38:41
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    PDF, 7.43 MB

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