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Western Hoolock gibbon (Hoolock hoolock) is an endangered ape species occur in the some selected reserve forest of Karimganj district, namely Patheria,Longai and Singla Reserve Forests of Assam since long .But over the last decade or so, no work was done on this species in the areas. Therefore a study was conducted in the Patheria Reserve Forest in order to study the population status and distribution of Western Hoolock gibbon (Hoolock hoolock). Initially survey was undertaken to identify the various habitats and thereafter population status and distribution were assessed. Population estimation was done by employing both census and auditory technique of survey. The study provides a direct evidence that there has been a declining in the population primarily due to habitat destruction and fragmentation because of setting up of a numbers of BSF outposts in the forest areas, construction of roads along the Indo-Bangladesh border and mass killing of the species by the tribal inhabitants of Reserve forest as they believed that the flesh and blood of gibbon have medicinal values.

1. To identify the distribution range of Western Hoolock gibbon(Hoolock hoolock) in Patheria Reserve Forest.

2. To determine the population status of gibbon in Patheria R.F.

3. To assess the probable cause of declining of gibbon population.

4. To identify the probable threats of gibbon across the habitat(Anthropogenic threats).

Western Hoolock Gibbon (Hoolock Hoolock) is listed as endangered ape species in the IUCN Red data list (A2acd+3cd+4acd) and listed in schedule-1 of the Indian wildlife (protection) Act 1972.This species has been on the list of the world’s 25 most endangered primate species since 2006 (Walker et al 2007).In 1967,it was first reported to occure in Assam(India).Since 1987,its population has started declining especially in Bangladesh and India>In India its distribution is restricted to south of Brahamaputra and East of Dibang river(Choudhury,2001a). Sati and Alfred (@001),IUCN (2004),reported that threat such as habitat loss and hunting are the primary cause of rapid decline in its number.

Molur et al (2003) pointed out that Gibbon are loosing 3-4% of their habitat every year and their population is declining by 1-2% every year  in their distribution range.Among the gibbons,Western Hoolock gibbon (Hoolock hoolock) are perhaps under the greates  threat  throughout their geographical range (Mootnick et al,1987),Mac Kinnon and Mac Kinnon,1987,Islam and Feeroz 1992,Feeroz 1999,2001,Choudhury 2001, Choudhury 2001a).

It is declared that no work in this particular area has been done other than the researcher. Almost all work on this particular area was done by researcher during his research work.

Study Area He present work was undertaken in the Patheria Reserve Forest of Karimganj district covering an area of about 7647.35 hectre.This reserve forest marks the western border of the district forming the International border with Bangladesh from south to North covering a length of about 28 miles.This Reserve forest range was predominated by semievergreen forest having varied food plants of gibbon Census Method: Census method was adopted during the course of study to ascertain the presence of gibbon.the distribution and status of gibbon in the Patheria reserve Forest was ascertained by direct sightings,by hearing theirs calls and also through interview with the local forest staff,villagers and poachers. The present field study was conducted from January 2022 to March 2023.During the course of field study line transact, Fixed point count(Point Census),gibbon call recording and auditory technique of surveying gibbon population (Brockelmann and Ali) was adopted simultaneously to confirm the places of occurance of gibbon. GPS reading was also recorded and the same was plotted in the map to show the exact location of their occurrence.

The present work provides an information that fair ly good number of Western Hoolock gibbon are still occurring in the Patheria Reserve Forest but as per report from indirect sources (Local forest staff, Villagers, people residing nearby  forest areas),the number has declined and is declining day by day due to anthropogenic  disturbances. Their survival is more at stake towards the trans-boundary between India and Bangladesh. The study also come up with observation that canopy destruction and hunting  is the main reason behind their  declining population causing survival stress. Other factors that contribute to the habitat destruction includes-i) setting up of number of B.S.F out posts in the forest area, ii) Construction of roads by the border security Forces along the border areas within the premises of the forest , iii) Illegal timber logging, iv) cutting of forest for timber and agricultural expansion within the Reserve forest.

 During the tenure of work as many as 16 locations were identified as the habitat of Western Hoolock gibbon in Patheria Reserve Forest. The exact location of the of the occurrence of Gibbon  was recorded with GPS .In the 16 different locations of gibbon occurance,18 different groups were observed with a total population of about 56 individuals. The group composition in almost  all group consists of single male, single Female with 2-3 babies.

The exact location, number of groups and individuals with age-sex composition observed during the course of the study in Patheria reserve Forest of Karimganj  district is as per table as under.                                              

Table-1

Sl. NO.	GPS Location	No of groups	Adults		Immature				Total	Avg. Group size
			M	F	SAM	SAF	JUV	INF
1	24˚44ʹ0.539ʺN 92˚17ʹ25.405ʺE	1	1	1	_	_	1	_	03	03
2	24˚43ʹ6.281ʺN 92˚17ʹ49.896ʺE	1	1	1	1	_	_	_	03	03
3	24˚42ʹ23.618ʺN 92˚17ʹ11.075ʺE	1	1	1	_	_	_	1	03	03
4	24˚41ʹ53.042ʺN 92˚17ʹ13.107ʺE	1	1	1	_	_	_	_	02	02
5	24˚41ʹ37.457ʺN 92˚16ʹ56.88ʺE	1	1	1	_	_	_	1	03	02
6	24˚39ʹ21.9543N 92˚16ʹ16.332ʺE	1	1	1	_	_	1	_	03	03
7	24˚39ʹ7.877ʺN 92˚16ʹ1.537ʺE	1	1	1	_	1	_	_	03	03
8	24˚37ʹ54.823ʺN 92˚16ʹ3.823ʺE	1	1	1	1	_	1	_	04	4
9	24˚37ʹ13.953ʺN 92˚15ʹ45.473ʺE	1	1	1	_	_	_	1	03	3
10	24˚36ʹ39.479”N 92˚14ʹ7.169ʺE	1	1	1	_	1	_	_	03	3
11	24˚36ʹ41.291ʺN 92˚14ʹ29.461ʺE	3	3	3	2	2	_	2	12	4
12	24˚36ʹ25.952ʺN 92˚14ʹ20.261ʺE	1	1	1	1	_	_	_	03	3
13	24˚36ʹ5.767ʺN 92˚15ʹ1.269ʺE	1	1	1	_	_	1	_	03	3
14	24˚36ʹ21.143ʺN 92˚15ʹ17.905ʺE	1	1	1	1	_	_	_	03	3
15	24˚35ʹ49.051ʺN 92˚15ʹ57.121ʺE	1	1	1	_	_	1	_	03	3
16	24˚33ʹ5.397ʺN 92˚14ʹ10.0326”E	1	1	1	_	_	_	1	03	2
Total		18	18	18	06	04	05	05	56	3.11

M=Male, F=Female, SAM=Semi adult male, SAF=Semi adult female, JUV=Juvenile, INF=Infant

 Table: Total no of groups and individuals with age-sex composition recorded from 16 surveyed localities in the Patharia R.F. of Karimganj district

 

 

                    

Figure 2:.Age-sex composition (%) of Hoolock gibbon in Patharia RF

This particular work was undertaken in the Patheria Reserve Forest of Karimganj district to assess the present population status of Western Hoolock gibbon (Hoolock hoolock) and its distribution therein in the forest range .During the work information was gathered from both direct and indirect source that the population of the species was decling day by day mainly because to destruction of habitat of gibbon due to human interference.However, presence of dense canopy in the trans boundary between India and Bangladesh and diversity of food plants are encouraging which perhaps the most important determinant for supporting the gibbon population but efforts are needed to protect the species in this reserve forest otherwise they will Not last long.

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