Research Article: Karanth, K. K., Nichols, J. D., & Hines, J. E. (2010). Occurrence and distribution of Indian primates. Biological Conservation, 143(12), 2891-2899.

 

Blog Author: Sikha Hariharan

 

Key Highlights:

  • Effective conservation relies on knowing where a species is found and why it is found in particular landscapes; this understanding is frequently impeded by unreliable range maps and inaccurate data.
  • Through advanced statistical methods and a country-wide survey, the authors developed distribution maps for 15 Indian primate species.
  • Protected areas, landscape characteristics, and human population influence primates’ presence, with varying impacts on different species.
  • Quality protected areas were crucially important for the Assamese macaque, Phayre’s leaf monkey, pig-tailed macaque, rhesus macaque, slender loris, slow loris, and stump-tailed macaque.
  • While Assamese macaques, bonnet macaques, rhesus macaques, slender lorises, and slow lorises avoided humans in certain regions, in other areas, bonnet macaques, rhesus macaques, Hanuman langur benefitted from the cultural tolerance. 
  • The study identifies vulnerable primate species and stresses the importance of protected areas, connectivity, landscape diversity, and community involvement, urging the use of advanced statistical methodologies in conservation efforts.

Primates play a crucial role in maintaining ecosystem balance through their activities such as seed dispersal, insect and small mammal predation, and pollination, among others. However, human-induced global changes threaten their survival. Knowing where a species is found and why is the cornerstone of any effective conservation effort. This is often hindered by the lack of reliable maps showing where different species are found (distribution maps) and what factors affect their presence and absence (occurrence) in particular landscapes. Mapping species regionally and globally is resource-intensive and time-consuming.

Dr. Krithi K. Karanth, from the Centre for Wildlife Studies, James D. Nichols from Colombia University, and James E. Hines from the US Geological Survey set out to rectify this issue by developing distribution maps of 15 Indian primate species and examining the factors influencing their occurrence. In 2006, a country-wide survey was conducted using the expert opinion of more than 100 Indian wildlife experts and analyzed using an ‘occupancy modeling framework’. Here, information is fed in the form of the ‘presence’ and ‘absence’ of a species indicated by ‘1s’ and ‘0s’, respectively, to calculate the geographic area occupied by a species. Its advantage lies in providing a distribution map that a species could be found at a location as a gradient of chance (‘probability’) using ‘imperfect detection’ — a presence confirms a species’ occurrence, while an absence indicates it wasn’t detected but doesn’t rule out its presence. The occupancy (or the presence-absence) model uses a grid-based approach, wherein the country was divided into 1326 grid cells, with 2 to 37 experts providing presence-absence data of a species per cell.

The authors considered three main factors influencing primate occurrences: protected areas, landscape characteristics, and human influences. Protected areas act as refuges, especially for range-restricted and threatened species; diverse forest types, land cover, and elevation are critical for specific primates; human population density and cultural tolerance affect primate adaptability and coexistence with humans. Not all covariates were used for all species; they were selected based on the geographic and ecological factors affecting each species, which were analyzed separately.

Results indicated that protected areas, such as national parks and wildlife sanctuaries, positively influenced the presence of seven primate species, namely the Assamese macaque, Phayre’s leaf monkey, pig-tailed macaque, rhesus macaque, slender loris, slow loris, and stump-tailed macaque. Evergreen forests were important habitats for seven species, while temperate forests were found to be important only for Assamese macaques. While deciduous forests were important for seven primate species, they were critically important only for Phayre’s leaf monkey and negatively influenced the presence of six others. Rhesus macaque, capped langur, and golden langur avoided higher elevations. Assamese macaque, bonnet macaque, rhesus macaque, slender loris, and slow loris were mainly found in areas with lower human population densities. Higher cultural tolerance favored the occurrence of bonnet macaques, rhesus macaques, Hanuman langur, and somewhat for slender loris; these species are also often found in rural and urban areas with high densities of people.

Hanuman langur and rhesus macaque had the widest distribution and occurrence. Except for these two species, all others occupied less than 15% of the total area. North-eastern species, such as the golden langur and Arunachal macaque, were the most range-restricted, meaning they occupied smaller geographical areas.

The study identified vulnerable primate species in need of urgent conservation, aligning with IUCN Red List categories. Protected areas serve as crucial refuges, yet they face fragmentation and encroachment, emphasizing the need for enhanced connectivity. Maintaining landscape diversity, fostering connectivity among protected areas, managing hunting threats, and promoting tolerant community practices are vital. The authors highlight the importance of incorporating advanced statistical methodologies like occupancy modeling into range maps and recommend further steps of estimating population abundance through field surveys to long-term monitoring.

Link to original article: click here

Keywords: Distribution, Extinction, Primates, Occupancy, India, Parks