Journal of
Threatened Taxa | www.threatenedtaxa.org | 26 January 2019 | 11(1): 13047–13057
Distribution of the threatened Assamese Macaque Macaca assamensis (Mammalia:
Primates: Cercopithecidae) population in Nepal
Laxman Khanal 1, Mukesh Kumar Chalise
2 & Xuelong Jiang 3
1,2 Central Department of Zoology, Institute
of Science and Technology, Tribhuvan University, Kirtipur, Kathmandu, Nepal.
1,3 Kunming Institute of Zoology, Chinese
Academy of Sciences, Jiaochang E Rd, Wuhua, Kunming, Yunnan 650223, China.
1 lkhanal@cdztu.edu.np (corresponding
author), 2 mkchalise@cdztu.edu.np, 3 jiangxl@mail.kiz.ac.cn
Abstract: Sustainable conservation and management of a species require detailed
knowledge of its population status and distribution pattern. The population of the Assamese Macaque Macaca
assamensis in Nepal, probably a new subspecies endemic to the country, is
yet to be studied for documenting its spatial distribution and size. We did extensive surveys across three major
river systems of Nepal (Koshi, Gandaki, and Karnali river systems) by modified
line transect method covering almost the entire distribution range of the
species within the Nepal territory. We
counted a total of 829 individuals in 43 groups that accounted for the average
group size of 19.29 (±10.40) individuals.
The elevation distribution of the species ranged between 130m and
2650m. Further, we assessed the
potential distribution areas of the species by ecological niche modeling employing
maximum entropy algorithm. The census
and ecological niche modeling congruently revealed the mid-hills of eastern and
central Nepal outside the protected areas as the major habitats of this
nationally endangered and protected primate.
Conservation attempts, therefore, should focus on this area.
Keywords: Ecological niche modeling, MaxEnt,
primates, spatial distribution.
doi: https://doi.org/10.11609/jott.4623.11.1.13047-13057
| ZooBank: urn:lsid:zoobank.org:pub:9E3E5F48-AB19-4203-B829-F5BDD2EE6616
Editor: Mewa Singh, University of Mysore, Mysuru, India. Date of publication: 26 January
2019 (online & print)
Manuscript details: #4623 |
Received 08 October 2018 | Final received 10 January 2019 | Finally accepted 15
January 2019
Citation: Khanal, L., M.K. Chalise & X. Jiang (2019). Distribution of the threatened Assamese Macaque Macaca assamensis
(Mammalia: Primates: Cercopithecidae) population in Nepal. Journal
of Threatened Taxa 11(1): 13047–13057; https://doi.org/10.11609/jott.4623.11.1.13047-13057
Copyright: Khanal et al. 2019. Creative Commons
Attribution 4.0 International License. JoTT allows unrestricted use,
reproduction, and distribution of this article in any medium by adequate credit
to the author(s) and the source of publication.
Funding: This study was supported by Rufford Small Grants Program
(ID 17666-1) of Rufford Foundation, UK; and Key Research Program of the Chinese
Academy of Sciences, Grant Number: KJZD-EW-L07.
Competing interests: The authors declare no competing interests.
Author
Details: Laxman Khanal, PhD, is Assistant Professor at Central
Department of Zoology, Institute of Science and Technology, Tribhuvan
University, Kathmandu. He got his PhD in Molecular Ecology and Evolution from
University of Chinese Academy of Sciences, China under CAS-TWAS President’s PhD
Fellowship Program. His research interests include phylogeny and phylogeography
of mammals, molecular ecology and conservation ecology. Mukesh
Kumar Chalise, PhD, is the Professor at Central Department of Zoology,
Institute of Science and Technology, Tribhuvan University, Kathmandu. He is the
pioneer primatologist and renown wildlife biologist in Nepal. He has also
worked as Visiting Professor in Kyoto University, Japan and Dali University,
Yunnan, China. Xuelong Jiang, PhD,
is the Professor at Kunming Institute of Zoology, University of Chinese Academy
of Sciences, China. His research mainly include
phylogeny and phylogeography of mammals, animal behavior, wildlife conservation
and management, etc.
Author
Contribution: LK, MKC and XJ
conceptualized the project. LK and MKC carried out the field
work. LK analyzed the data and prepared the manuscript. MKC and XJ
supervised the overall research and contributed in manuscript improvement.
Acknowledgements: The fieldworks were partly supported by the Rufford Small Grants of
Rufford Foundation, UK and Key Research Program of the Chinese Academy of
Sciences, Grant number: KJZD-EW-L07. We
extend our sincere thanks to the Department of National Parks and Wildlife
Conservation, and Department of Forest, Ministry of Forest and Soil
Conservation, Government of Nepal for permitting the field research. We are thankful to our field assistants –
Dhirendra B. Chand, Sunil Khatiwada, Pavan Paudel, Shivish Bhandari, Sabin
Pandey and all the local people who helped us in the field.
Introduction
An
accurate assessment of population densities in natural habitats is the
prerequisite for the determination of priorities for the sustainable
conservation and management of a species (Defler & Pintor 1985; Kumara
& Radhakrishna 2013). Primate census
is useful in the conservation of a species as it provides multiple benefits
such as i) population density or total counts that can be the baseline
information for future monitoring, ii) evaluation of population changes since a
previous census period, if any, iii) an assessment of population tendency with
support of frequent censuses, and iv) an evaluation of different habitats for
their relative importance in primate conservation. Such assessments can help conservation managers
judge the success of the ongoing management activities and decide when, where,
and how to mediate for the management of a species (Plumptre & Cox
2006).
Multiple
direct and indirect methods are available to understand and monitor species
presence and abundance. These include
the total count of individuals, strip transects, line transects, capture-mark-recapture methods, and observations of signs like
feces, nests, and tracks (Kumara & Radhakrishna 2013). The results from different methods vary and
using different census techniques together add unknown errors. Hence, it is necessary to develop uniform
methods that can be replicated over time and space to monitor the primate
populations for their conservation (Plumptre & Cox 2006). Census by total count is the most reliable
method since it is highly informative and accurate if the assumption that all
individuals present in the group are counted once and no individual is
double-counted is not violated (Kuhl et al. 2008).
Determining
the spatial distribution of a species is a multifaceted task (Boubli & de
Lima 2009). Species distribution
modeling (SDM), also known as ecological niche modeling (ENM), can be coupled
with the systematic survey of species presence to identify the potential
distribution range of the species (Ortega-Huerta & Peterson 2008) relating
the field observations to environment layers of predictor variables (Guisan
& Thuiller 2005). SDMs establish
relationships of known species occurrences with potential environment
covariates and then predict the spatial and temporal distribution of the
species. Among the SDM techniques
available at present, maximum entropy method or MaxEnt (Phillips et al. 2004)
is designed to depict the distribution of individual species using
presence-only data (Phillips et al. 2006).
It outperforms other existing predictive methods (Elith et al. 2006) and
shows exponential growth in its application since its introduction in 2004
(Morales et al. 2017). The tool was used
in many taxa including primates for multiple purposes including mapping
potential distribution and habitat use (Boubli & de Lima 2009; Norris et
al. 2011; Vidal-Garcia & Serio-Silva 2011; Voskamp et al. 2014; Sarma et
al. 2015; Sarania et al. 2016), delineating ecological boundaries of multiple
taxa (Nag et al. 2014), assessing threats and setting conservation priorities
(Thorn et al. 2009; Campos & Jack 2013), paleodistribution reconstruction
and phylogeography (Khanal et al. 2018a,b), and range shifts (Elith et al.
2010).
The
Assamese Macaque Macaca assamensis McClelland, 1840 is one of the
members of polytypic Sinica-group of macaques that is characterized by
the sagittate-shaped glans penis and that has a fragmented distribution in
southern and southeastern Asia. Assamese
Macaques are medium-sized, arboreal, diurnal, and omnivorous cercopithecine
primates that live in multimale-multifemale social groups (Chalise 1999; Molur
et al. 2003). It has two known
subspecies, Eastern Assamese Macaque M. a. assamensis and
Western Assamese Macaque M. a. pelops,
the distribution ranges of which are demarcated by the Brahmaputra River (Roos
et al. 2014). The Assamese Macaque
population in Nepal differs in pelage and facial color, relative tail length,
and elevation distribution range to their nearest conspecific populations (M.
a. pelops) from the adjacent countries such as India and Bhutan. Thus, the Nepalese population of Assamese
Macaque was doubted for a distinct subspecies status and referred to as ‘M.
assamensis Nepal population’ (Molur et al. 2003; Chalise 2005, 2013;
Boonratana et al. 2008).
The
Assamese Macaque is categorized as Near Threatened by the IUCN (Boonratana et
al. 2008) and its Nepalese population, one of the least studied primates, is
nationally listed as Endangered due to its restricted distribution, population
threats, and small numbers in fragmented patches of the remaining habitat. Thus, the species is protected by the
National Park and Wildlife Protection Act 1973 of Nepal (Boonratana et al.
2008; Chalise 2013; Chalise et al. 2013).
It was reported from the mid-hills within Nepal as a sub-tropical
habitat specialist, but the details on its socioecology are yet to be
documented (Khanal et al. 2018a).
The
distribution and conservation status of the Assamese Macaque in Nepal is not
well documented. Wada (2005) surveyed
the distribution of Assamese Macaque in Nepal and reported it from only the
east of Kaligandaki River. The studies
so far in Nepal (Chalise 1999, 2008, 2013; Chalise et al. 2005; Wada 2005) were
confined to surveying the fragmented populations of Assamese Macaque at
different patches, lacking a systematic study that covers the entire range of
the species. Although it is listed as an
endangered species and is protected nationally, the species was described as a
crop-raider in some parts of Nepal (Chalise 2010; Paudel 2017; Adhikari et al.
2018). Most of the habitats of the
species fall outside the protected areas in mid-hills and no detailed
documentation of population and distribution was done
so far. Therefore, it is crucial to
identify the population status, distribution pattern, and conservation status
of Assamese Macaque in Nepal.
We
aimed to explore the population status, distribution pattern, and the
potentially suitable habitats of the Assamese Macaque in Nepal. We did an extensive survey along the
tributaries of the three major river systems of Nepal from September 2015 to
October 2016 covering almost the entire distribution of the species and
performed a population census. We used
the census points of the species and bioclimatic variables to determine their
potential distribution areas. Here, for
the first time, we describe that the westernmost distribution limit of the
Assamese Macaque, as described in previous publications (Fooden 1979, 1982;
Wada 2005; Timmins & Duckworth 2013), is not the Kaligandaki River of
central Nepal. We recorded three groups
from far western Nepal and censused them.
Materials and
Methods
Study Area
Nepal
stands on 26.350–30.4500N & 80.067–88.2000E (Sharma 1999). It extends about 800km along the east-west
Himalayan axis and its width varies between 150km and 250km, covering a total
area of 1,47,181km2. The
Nepal Himalaya forms the central one-third of the entire Himalayan range and
includes multiple bioclimate zones. It
has geographic diversity ranging from 60m elevation in
the tropical Tarai beyond the perpetual snow line to over 7,000m
including Earth’s highest 8,848m (Mount Everest) (Khanal et al. 2018a). Wide
altitude variations and diverse climate conditions resulted in five main
physiographic zones within Nepal (Table 1) (Carson et al. 1986) and such
extreme altitude gradients created nine bio-climatic zones ranging from
tropical to nival (Fig. 1A) (HMGN/MFSC, 2002).
Assamese
Macaques were reported in Nepal from 300m to 2,350m (Chalise 2013) that includes the Siwalik Hills, lower mid-hills, and upper
mid-hills. Surveys were conducted in
three physiographic zones (Tarai, mid-hills, and lower Himalaya) across the
three major river systems — Nepal-Koshi River system in eastern Nepal, Gandaki
River system in central Nepal, and Karnali-Mahakali River system in western
Nepal (Fig. 1A).
It
included mid-hills and the lower-Himalaya region of eight protected areas of
Nepal and non-protected Assam Macaque habitats in the mid-hills. The Tarai and Siwalik zone below 1,000m has
tropical forests that can be categorized as Shorea robusta forest, Acacia
catechu-Dalbergia sissoo forest, other riverine forest, and Terminalia-Anogeissus
deciduous hill forest. The mid-hills
bear sub-tropical forest up to 1,700m dominated by Pinus roxburghii, Schima-castanopsis,
and Alnus nepalensis and riverine forest with Toona and Albizia
species. The areas from 1,700m to 2,700m
bear lower temperate forest dominated by Quercus leucotricophora, Q.
lanata, Q. floribunda, Q. lamellose, abundant lauraceae, and Pinus
wallichiiana (Jackson 1994). The
lesser Himalaya has temperate forests dominated by the Quercus-pine-rhododendron
combination (Chalise et al. 2005; Khanal et al. 2018b).
Field Survey Design
The
standard method for counting predominantly arboreal monkeys is along the
line-transects (Marshall et al. 2008).
Spatial distributions of study species in the four physiographic zones
across the river systems were surveyed by a modified line-transect method
(Buckland et al. 2010). Two line-transects, each of 5km length, were used on either
side of the rivers and their tributaries in each physiographic zone (Fig. 1B;
2).
The
line-transects were roughly parallel to the river
axis. The first transect was within 1km
and the second transect was within 4–5 km perpendicular distance from the river
center. The Tamor, Arun, and Sunkoshi
rivers of Koshi River system, Trishuli-Budhigandaki, Marshyangdi, and
Kaligandaki of Gandaki River system, and Bheri, Karnali, and Chamelia rivers of
Karnali-Mahakali River system were surveyed.
A total of 48 line-transects were surveyed in
each river system. In addition to the
river systems, surveys were also done in Shivapuri Nagarjun National Park that
lies in the mid-hills between Koshi River system and Gandaki River System.
Population Survey
We
conducted our field survey between September 2015 and October 2016. Wherever the groups were observed, detailed
population censuses were conducted. A
closely bonded social assemblage of monkeys sharing resources, at least 200m
apart from the nearest assembly, was considered a group (Chalise 2005; Lehmann
& Dunbar 2009). The geographic
location of the group was noted using GPS and vegetation samplings were done
using 20m × 20m quadrates. Distances of
group occurrence from the nearest river, human settlement, and crop fields and
other relevant measurements were noted.
The group size and population composition were observed in detail from a
distance varying from about 10m to 100m aided with binoculars whenever
necessary. The individuals were divided
into four age groups, namely, adults (male and female), sub-adults, juveniles,
and infants, following the method of Chalise (2003). The counting was repeated until the
concurrent readings were obtained for total count and age groups. On encountering the signs confirmed for
Assamese Macaque, even if the group was not observed, the GPS locations were
noted and the vegetation survey was done.
Data Analysis
Estimation of Population Parameters
Male to
female sex ratios were calculated among the adult and sub-adult age groups
separately as the number of males out of 100 females. Infant to female ratio was calculated by
dividing the total number of infants by the total number of adult females in the
group. The average group size was
computed as the mean of the number of individuals among the observed groups.
Total number of individuals observed
Average group =
––––––––––––––––––––––––––––––
Total number of groups observed
Number
of males of that age group
Sex ratio (male: female) =
–––––––––––––––––––––––––––––
Number of females of same age group
Total number of
infants
Infant female ratio =
–––––––––––––––––––––––––––––––––
Total number of females in reproductive
age groups
The
number of individuals varied among the different groups and the group size data
was tested for normal distribution by Shapiro-Wilk test. It revealed that the data were not normally
distributed (W=0.941, P=0.029), hence, they were normalized first and then the
significant difference in group size among the three river systems was tested
statistically by One-way ANOVA using Graphpad Prism v.5.01 (Motulsky 1999).
Distribution pattern
The
number of groups and individuals observed were categorized based on their
presence at different river systems and elevation zones. The statistical significance of the
differences in their distribution pattern was tested by one-way ANOVA.
Population distribution in protected and
non-protected areas
To
assess the conservation status of the Assamese Macaque, the total population
observed was subdivided to two groups — population inside protected areas
(national parks and buffer zones, conservation areas, wildlife reserves, and
hunting reserves) and population outside protected areas. The significant difference in the group size
between the two populations was tested by t-test.
Ecological niche modeling
The 19
bioclimatic variables (version 1.4) (Table 2) in a 30 arc second spatial
resolution representing the present bioclimatic conditions were retrieved from
the WorldClim global climate database portal (WorldClim 2018). For the ecological niche modeling (ENM) of
the Assamese Macaque, the geographic coordinates of the 43 groups collected
using GPS during the field surveys were used.
The Nepalese population of Assamese Macaques are considered endemic to
Nepal. Therefore, for modeling their
distribution, all bioclimatic variables were clipped to the boundary of Nepal
using ArcGIS 10.3.1 and exported in ASCII format. Seven bioclimatic variables (Bio: 1, 3, 5,
11, 12, 15, 18) were selected for the ENM after removing highly correlated (r ≥
|0.8|) variables on the Pearson correlation test (P <0.05).
MaxEnt
v.3.4.1 (Phillips et al. 2006) was used to model and map the current potential
distribution of M. assamensis.
For model evaluation purposes, the species presence data were randomly
divided into 75% as the training dataset and 25% as the validation
dataset. To account for uncertainty introduced
by training and validation set splits, 25 replicated models based on the
cross-validation method were generated (Otto-Bliesner et al. 2006). The accuracy of the models was evaluated by
using the area under the curve (AUC) of the receiving operating curve (ROC).
The
logistic output of habitat suitability was
converted to the binary output of unsuitable and suitable habitats using
the threshold of maximum training specificity and sensitivity (maxTSS=0.348) as
explained for the model generated by presence-only data by Liu et al.
(2013). Then, the potential altitude
range of suitable habitats was evaluated by overlaying the binary output on the
SRTM DEM (Jarvis et al. 2008). The
elevations of the suitable habitat pixels were extracted and their mean,
maximum, and minimum were computed.
Table 1. Five major
physiographic zones of Nepal (Source: Carson et al. 1986).
Physiographic Zone |
Area (%) |
Elevation (m) |
Climate |
High Himalaya |
23 |
above 5,000 |
Tundra-type, Arctic, and Trans-Himalayan |
High mountains |
20 |
4,000–5,000 3,000–4,000 |
Alpine Sub-alpine |
Mid-hills |
30 |
2,000–3,000 1,000–2,000 |
Cool temperate monsoon Warm temperate monsoon |
Siwalik Hills |
13 |
300–1,000 |
Hot monsoon and subtropical |
Tarai |
14 |
< 300 |
Hot monsoon and tropical |
Results
Total population and river system-wise
distribution of Assamese Macaque in Nepal
A total
of 829 individuals of Assamese Macaques from 43 groups were observed during the
field survey. The highest number of
groups and individuals were observed from Gandaki River system (21 groups and
377 individuals) in central Nepal, followed by the Koshi River system (13
groups and 287 individuals), Shivapuri Nagarjun National Park (six groups, 104
individuals), and Karnali-Mahakali River system (three groups and 61
individuals) (Figs. 2 & 3). The
overall average group size was calculated to be 19.29 (±10.40). The groups varied in their sizes and ranged
between three to 39 individuals per group; however, variations were not
significant among the four study areas (One-way ANOVA, F=0.448; df=(3, 39); P=0.692). The highest average group size was computed
from Koshi River system (22.07±11.73 individuals per group) and the lowest from
Shivapuri Nagarjun National Park (17.33±10.13 individuals per group).
Age-sex composition
The
overall adult to young ratio was computed to be 1:1.037, i.e., close to 1:1
ratio. The adult male to female sex
ratio was found to be 1:1.91 and the infants to adult female ratio was 0.592:1. The adult to young ratio and adult male to
female sex ratio did not vary among the groups of different river systems
[One-way ANOVA; adult sex ratio: F=1.050, df= (3,39), P= 0.381; adult to
young ratio: F= 1.554, df= (3,39), P= 0.216].
Elevation-wise distribution
The
Assamese Macaque groups were recorded across in the elevation range from 130m
at Chatara in eastern Nepal to 2,650m at Langtang National Park in central
Nepal. More than one-third of the groups
(34.88%) were recorded from the elevation ranges between 1,001m and 1,500m
while the highest number of individuals were observed
from elevations less than 500m.
Population distribution did not vary at different elevation zones of the
four study areas (Fig. 4) (F=2.199; df=(3, 16); P=0.127).
The
average group size was the highest (22.88 individuals per group) for the
elevation range of 501–1000 m and the least (15 individuals per group) for the
elevation range of 1501–2000 m (Table 3).
There, however, was no significant difference in the group size at
various elevation ranges (F=0.758; df=(4, 38); P=0.558).
Population distribution in protected and
non-protected areas
Out of
the total 829 individuals counted from 43 groups of Nepal territory (Fig. 3),
22 groups accounting for 407 individuals were observed from protected areas
(PAs, national park or conservation area), whereas 422 individuals from 21
groups were observed outside the protected areas. It accounted the average group size of 18.5
±10.24 and 20.1 ±10.77 individuals per group for inside and outside the PAs,
respectively; however, there was no significant difference in
group size between the populations inside and outside the protected
areas (t= 0.497, df=41, P= 0.621).
Ecological Niche of the Assamese Macaque
The
MaxEnt model generated for the Assamese Macaque performed well with a mean AUC
value of 0.899 ± 0.064 (Fig. 5B) for 25-fold cross validation indicating the
robustness in prediction of distribution of suitable habitat (Fig. 6). The prediction of habitat suitability
completely matched with the prevailing distribution records of the Assamese Macaque
within Nepal territory. Among the eight
predictive bioclimatic variables, precipitation of warmest quarter of the year
(bio18, 67.7%) contributed the highest to the model, followed by the
isothermality (bio3, 21.2%) and annual mean temperature (bio1, 4.2%).
The
Jackknife test of MaxEnt model (Fig. 5A) on variable importance showed that
bio18 (precipitation of warmest quarter) has the highest gain when it is used
in isolation. It validated that bio18
has the maximum useful information among the variables and contributed most to
the model development. Further, omission
of bio18 decreased the gain of model indicating that it holds the most
information for Assamese Macaque suitable habitat determination among the
variables used for the model development.
According to the response curve plots, the precipitation of warmest
quarter above 1200mm and isothermality around 50 were ideal to define the
suitable habitat for Assamese Macaque
(Fig. 5C). Such conditions are
fulfilled by the mid-hills of central Nepal supporting the broad-leaved
vegetations.
The
MaxEnt model predicted potential habitat of Assamese Macaque within the
elevation range between 85m and 2,987m.
The mean height of the potential habitat was found to be 1532m, however,
maximum number of suitable habitat pixels (55.03%) were predicted from the
elevation range between 500m and 1,500m.
Currently, 23.49% area of Nepal territory is potential habitat of the
Assamese Macaque.
Table 2. Bioclimatic variables used in
the construction of ENM for Assamese Macaque
|
Abbreviation |
Description |
1* |
Bio1 |
Annual mean temperature |
2 |
Bio2 |
Mean diurnal range [mean of monthly (max
temp–min temp)] |
3* |
Bio3 |
Isothermality (P2/P7) (×100) |
4 |
Bio4 |
Temperature seasonality (standard
deviation × 100) |
5* |
Bio5 |
Max. temperature
of warmest month |
6 |
Bio6 |
Min. temperature of coldest month |
7 |
Bio7 |
Temperature annual range (P5–P6) |
8 |
Bio8 |
Mean temperature of wettest quarter |
9 |
Bio9 |
Mean temperature of driest quarter |
10 |
Bio10 |
Mean temperature of warmest quarter |
11* |
Bio11 |
Mean temperature of coldest quarter |
12* |
Bio12 |
Annual precipitation |
13 |
Bio13 |
Precipitation of wettest month |
14 |
Bio14 |
Precipitation of driest month |
15* |
Bio15 |
Precipitation seasonality (coefficient
of variation) |
16 |
Bio16 |
Precipitation of wettest quarter |
17 |
Bio17 |
Precipitation of driest quarter |
18* |
Bio18 |
Precipitation of warmest quarter |
19 |
Bio19 |
Precipitation of coldest quarter |
Table 3. Average group size of Assamese
Macaque population at different elevation gradients.
|
Elevation range |
No. of groups |
Total population |
Average group size (SD) |
1 |
< 500m |
13 |
280 |
21.54 (±10.62) |
2 |
501–1000 m |
8 |
183 |
22.88 (±13.57) |
3 |
1001–1500 m |
15 |
250 |
16.66 (±9.87) |
4 |
1501–2000 m |
3 |
45 |
15 (±7.99) |
5 |
> 2000m |
4 |
71 |
17.75 (±4.99) |
Discussion
Assamese
Macaques are the least researched primates in Nepal Himalaya. They are distributed in subtropical and
temperate zones (Chalise 2013). Because
of the limited and unsystematic studies, population status
and distribution patterns of this species is poorly documented. For the successful conservation and
management of such primates it is crucial to have basic data on their
demographic status and spatial extents of distribution.
Assamese
Macaques are sporadically distributed across the fragmented forest patches in
Nepal. Wada (2005) recorded a total of
10 groups of Assamese Macaques distributed only east of the Kaligandaki Valley
in central Nepal, within the elevation range of 200–1,800 m. In the most recent study, Chalise (2013)
recorded a total of 1099 individuals in 51 groups from 380m to 2350m. Both of those studies failed to cover the
spatial and temporal facets of demographic research, as the work of Wada (2005)
was confined only along
six rivers and that of Chalise (2013) was the accumulation of
observations at different time periods during last two decades. This study considered both the spatial and
temporal aspects and did systematic survey across the entire distribution range
of the species within a calendar year.
It recorded a total of 829 individuals of Assamese Macaque from 43
groups.
Current
average group size of Assamese Macaque (19.29 individuals per group) was
consistent with that of Wada (2005), i.e., 19.1; however, it differed with that
of Chalise (2013), 21.55 individuals per group, that
might be accounted to the temporal variations in their observation as the
observations were made at different periods within last two decades. The organisms are restricted to specific
altitudinal ranges as a consequence of microclimatic limitations imposed by
ambient temperature and humidity on species metabolisms and on their
phenological preferences (Sekercioglu et al. 2008). Wada (2005) reported larger average group
size of Assamese Macaques on lower elevations than that of mid-hills. In the present study, the population size of
Assamese Macaque differed significantly at different elevation ranges, however, no such significant variations on average
group size were recorded along the elevation gradients. Wada (2005) reported the distribution range
of the species in between 200m and 1,800m, whereas Chalise (2013) explained
that of 380m and 2,350m. The present
elevation range of distribution (130–2,650 m) also differed with those studies,
it was consistently wider both on lower and upper limits. It shows that the species is experiencing the
elevational range expansion, especially towards the higher elevation.
This
study observed the highest number of groups and individuals from Gandaki River
system (21 groups and 377 individuals) in central Nepal followed by the Koshi
River system (13 groups and 287 individuals).
It revealed the central Nepal to be the glacial refugia for Assamese
Macaques which had eastward range expansion after LGM as revealed by the
molecular data and ecological niche modeling (Khanal et al. 2018a). Eastern and central Nepal receives higher
amount of precipitation from summer monsoon than the western Nepal (Owen et al.
2005), such higher precipitation might facilitate the grow
of broadleaf forest in mid-hills which is the most preferred habitat of the
species. Additionally, Assamese Macaques entered the Nepal Himalaya from south-east Asian ancestral stock via northeastern India
(Khanal et al. 2018a) that may be the principal reason of the higher density of
the species in eastern and central Nepal.
The
ecological niche modeling results were consistent with the observed
distribution pattern of the Assamese Macaque in Nepal Himalaya. It predicted suitable habitats on Siwaliks,
mid-hills and lower Himalaya of eastern and central Nepal including the areas
of Koshi River and Gandaki River systems, in majority. Using the DNA sequences analyses and niche
modeling, Khanal et al. (2018a) reported potential glacial refugia at central
Nepal and the expansion of population as well as the species
range after the last glacial maximum.
Many studies (Wada 2005; Chalise 2013) including the most recent one by
Regmi et al. (2018) employing field surveys and ENM reported the westernmost
limit of the Assamese Macaque to be the Kaligandaki River at central Nepal,
however, during this study some groups of the species were observed from far
western Nepal too. The occurrence points
employed in the model development are evenly scattered avoiding the sampling
bias, and the distributional model developed incorporated all the observed
points depicting the robustness of the prediction. The observed elevational range of Assamese
Macaque fell within that of the predicted habitat.
A very
high percent (~79%) of Asian primate species are threatened with the global
extinction (Schipper et al. 2008). Such
a high level of threat echoes extreme hunting pressure and habitat depletion
impacts (Primack 2006). It may be
especially alarming for those species which have small
populations and limited geographic ranges (Rovero et al. 2015). Assamese Macaques are considered nationally
endangered and are protected by the National Park and Wildlife Protection Act
1973 of Nepal (Khanal et al. 2018a).
There are limited protected areas in mid hills of Nepal, so most of the
primate habitats lie outside the protected areas and they are under severe
anthropogenic influences (Chalise 2013).
This study revealed that more than half of the Assamese Macaque
population resides outside the protected area system of the country. The mid-hills area with amenable temperature
and ample precipitation provide the suitable habitat for Assamese Macaque
(Khanal et al. 2018a), but that remains outside the protected area system of
the country. Because of this, at many
places of the mid-hill districts the species has been described as the notorious
crop raiders bringing them into negative interactions with subsistence farmers
(Chalise 1999, 2003, 2010, 2013).
Extending protected areas benefits to resource-dependent smaller
landholders who experience higher losses from human-wildlife conflicts (Karanth
& Nepal 2012). Establishment of
protected areas in mid hills would conserve the Assamese Macaque habitat
together with other plant and animal species.
Conclusion
We
conclude that Assamese Macaque population in Nepal is distributed within the narrow
elevational range especially at the mid-hills.
The population is sporadically distributed at fragmented forest patches
of the mixed riverine broadleaved forests.
More than half of the Assamese Macaque population is resided outside the
protected areas of mid-hills within which most of the suitable habitats of the
species fall; therefore, conservation efforts should be focused in those areas.
For
images/figures -- click here
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