Survey of the Smooth Indian Otter Lutra perspicillata in the Karnali   River of Royal Bardia National Park, Nepal 

Introduction 

The otters, at the apex of food web, are good indicator species of health status of riverine ecosystems it inhabit (Foster-Turley, et.al. 1990). Otters are semi-aquatic animals depend mainly on freshwater habitat. The smooth otter essentially associated with fresh water habitat and requires undisturbed forest and scrub adjacent to the water for security. In Nepal this species known to exists in the Koshi, Narayany, Karnali, and Mahakali River systems (Suwal 1995, and Shrestha 1997).

Although protected under the aquatic animal protection act, the smooth otter is data deficient and most threatened species in Nepal. Some anecdotal evidences suggest that the population is declining rapidly in the country. Currently they are facing immense pressure in four fronts: degradation and loss of riparian habitat, poaching for their pelts, disturbance by human activities and their feeding behaviour brings them direct conflicts with fisherman, who saw otter competitor for fishing. As a result they are surviving in fragmented population in some isolated areas. 

This is this preliminary report of the study and this report concentrates mainly on status, distribution and threats, and preliminary findings of the field research conducted in April 2002 and June 2002.

Objective 

The broad objective of the current research is to assess status and ecology L. perspicillata in order to develop sound management program for the conservation of residual population of the otter species in the country. The specific objectives are to:

1. Determine status and distribution,

2. Assess habitat utilization patterns,

3. Quantify activity patterns, and

4. Evaluate threats

Study Area 

Physiography 

The study area is the Royal Bardia National Park (RBNP) of western Terai, Nepal (approx. 28 deg.15’ to 28 deg.44’ N and 81 deg. 10’ to 81 deg. 45’ E). Present study is being conducted on the banks of Karnali River. River Karnali is originated from the Himalayas. Large parts of the river are flowing in the very steep gorge in the mountain. In lowland Terai the river diverges into the Geruwa and Karnali branches, each of these branches is further sub divided into number of channels making different islands between these channels. The Geruwa branch contains the greater flow and is the main study site. The Geruwa forms western boundary of the Royal Bardia National Park.

Climate: The lower Karnali basin has humid, warm, summer monsoon climate with a four-month rainy season starting in mid- June. Rainfall is approximately 1,300 to 2,099 mm. Most of the annual precipitation occurs during four months of the year (June- September). Temperature ranges from 8.6Ί c in the winter to 43Ί c in the summer. There is a difference in temperatures and rainfall in the southern and northern region of the river.  

Vegetation

The eastern bank of Geruwa River in is covered by well-protected park’s luxuriant vegetation consisting of Shorea robusta, Terminalia tomentosa, Adina cordifolia, Buchanania latifolia, Syzigium cumini,etc.   Other forest types include riverine khair-sisso forest and riverine grasslands.  The western bank of the Geruwa River occupies by agricultural lands. 

Wildlife

Royal Bardia National Park supports unique wildlife species including many endangered wildlife species including rhinoceros, elephant and tiger. The Geruwa river is inhabited by Platanista gangetica, Lutra perspicillata, Gavialis gangeticus, Crocodylus palustris, various species of turtles.  

Human dimension

Human settlement around the boarder of the park has been confined along the southern and western boundaries. VDCs bordering the southern and western boundaries have declared as buffer zone.

Methods 

1. Reconnaissance survey: A preliminary survey of the study area was carried out to find out the likely otter areas before the actual fieldwork started. Questioning local people including nature guide, farmer, and fisherman superficially did preliminary study.

2. Interviews: As a part of Otter survey, interviews were conducted with local people including nature guide, farmer, and fisherman during field surveys to sought information on population location, activity, and threats. Interviews consisted of: (1) having people identify local aquatic mammals from pictures, (2) asking for physical description of otter, (3) asking about relative abundances of otter in the area (i.e. rare, common, abundant, very abundant). Questioning was oral, informal and cantered on laminated photocopies of plates in Prater (1993) and Robertes (1997).

3. Field Survey and division of the river: Two field surveys were conducted one in between 18-31 April and second in between 2-14 June 2002 on both banks of Karnali (Geruwa) River to observe otter population and evidences such as spraints, footprints, resting sites, dens, etc for habitat assessment. Binocular was used to locate otter population. For the field study Karnali (Geruwa) River has been divided into two different blocks: block 1- north of east west highway and block 2- south of highway. During field survey information on habitat features such as landform element (streams, rivers, river channels, oxbow lakes, proximity to water body from sign locations, etc.), vegetation associations, size and configurations of dens, ongoing human activities, and threats facing by otters were recorded. All identified locations were spotted on the topographic maps

Result and Discussion 

The field researches have been conducted between 18-31 April 2002 and June 2002 to determine status and distribution, to assess habitat quality and to evaluate threats facing by otters in River Karnali (Geruwa). Field research includes interviews and survey. 

Status and distribution 

All the interviews (n= 25) knew that the smooth otter well. They informed before ten years the smooth otters were common in this region, but now it becoming rare outside of the protected area due to anthropogenic causes. Respondents reported to be present in the main river in the dry season, while in rainy season otters were range widely into smaller channels of the river and other wetlands inside the park.  

It has been found that the smooth otters are rare outside the Royal Bardia National park’s border in the Karnali River, while in river flowing inside the park they are still common. A minimum number of 35 smooth otter were estimated for Geruwa River in Royal Bardia National Park. The population was divided into five different sub populations. Among them Lalmati area,     

Gola ghat area and Khaurahi Khola were estimated to have the highier number of animals. Other evidences of otter’s presence such as spraints, dens and resting sites have supported this fact.  

Table 1. Otters and their evidences recorded in Karnali River bank, Nepal 

 * Informed by local nature guide

Spraints Distribution: Otter spraints were found in the various sites of the Karnali riverbank. Two types of sprainting behaviour have been identified on the basis of sprainting sites. 

(i)                  Single or small collection of spraints: These were found commonly on prominent rocks, logs, or on sand bars.  Single spraints were located in an area close to each other and situated within five meters from the river.

(i)                  Multiple Spraints: These were found on dry sandy banks or sand and pebble banks. Multiple spraints were found at least five meters far from the river edge.

Population Trend 

The results from the questionnaire survey showed a declining trend of otter in north and western bank of the Karnali River.

Habitat utilization  

North of East- West High way

In the north of east- west highway following three locations of smooth otter were identified in Karnali River bank. 

1. Damakantar (approx; 28⁰ 42’’N and 81⁰ 30’’E): An old, abandoned, den with entrance of about 30x 45cm was observed. It was located on a steep muddy bank, 2.5 meters above from the river.

2. Banka (approx: 28 ⁰ 41’’N and 81⁰ 30’’E): Scats suggesting few months old were observed on rocks. It was located three meters far from the river. No other evidences of otter presence were recorded from that area.
3. Bung ghat (approx: 28⁰ 40’’N and 81⁰ 17’ 30’’E): In April, a group of otters composed of two adults and two-sub adult were observed fishing near the confluence of Karnali with Bung khola, a small tributary of Karnali. All animals were extremely shy and swam quickly away from the boat. A den with an entrance of about 40x60cm was found located on the muddy bank beneath a big rock in the eastern side of river. Small collections of fresh spraints were also observed close to the den. 

   South of East west high way

   The eastern bank of the Geruwa River has excellent habitat for otter and other species of wildlife. Questionnaire survey and field study indicated that some fragmented populations of otter are survived in this section of the River.  In the south of east west high way following four sites were identified as habitat for otter.  

   1.      Lalmati area (approx. 28⁰ 35’’N and 81⁰ 16’’E): In the Lalmati area the river is meandering. On the east side of the river the land is covered by riverine forest, grass and bush. A group of otter was observed on the western side lalmati camp. They were seen fishing in hydraulic refuge created by wooden derbies. A den with the entrance of about 40x60cm was found located on the muddy bank beneath a big tree (DBH 75 cm) and overhanging vegetation covered the site.  

   2.      Danpur area (approx.28⁰ 31.30’’N and 81⁰ 15’’E): Smooth otter (N= 5) were seen in east side of Danpur. They swam away quickly when we approached close to the site. On the east bank there was a group fresh scats suggesting multiple sprainting site. 

   3.      Gola ghat area (approx. 28⁰ 30’’N and 81⁰ 14’’E and): There are numerous islands in between different channels of the Karnali River, riverine forest on the east and bush area, and riverine forest covered the islands. Close to Gola ghat area we have seen a group otters consisting of 8 individuals swimming and fishing. 

   4.      Khaurahi Khola (28⁰ 26 30”N and 81⁰ 14”E): A nature guide informed us that he observed a group of otters in Kaurahi khola in winter month. We could not observed otters in that area, but old scats were present suggesting the area was preferred habitat during wet season when water level in the river is sufficient. 

   The southern part of the river has good habitat for otter distribution, which was suggested by animal presence and their evidences. Scats from different location have been collected for analysis.  

   Threats

   Respondents identified fishing, stone mining, poaching for their pelts, degradation and loss of riparian habitat especially in western bank of the river, and disturbance by other human activities are major threats for otters

    

   1. Fishing: Fishing activities are common in west bank of river and south of national park border. It has been reported that there are commercial fishing in southern section of the river. Human fishing activity is major factor to decline otter in Geruwa River.
   2. Stone mining: Stone mining is common practice along the western bank and southern section of the river. District development committee is receiving revenue from the stone collectors. 
   3. Habitat destruction: The riparian habitat in the western bank of river is subject to degradation for human use.
   4. Disturbances: Human activities such as washing, bathing, fishing, boating, all are common practice in Karnali River. Theses practices are prime cause for otter decline in the Karnali River.

   Conclusion

   Within 35-kilometer stretch of the Karnali river under study there is considerable variation in the river’s topography, habitat features, otter distribution and threats. The rivers topography most likely affects the prey availability and thus distribution of otter. The south of Chisapani Bridge the river is braided into a number of channels by islands characterize by sandy stretches where water is slow flowing and frequent hydraulic refuge created by wooden derbies. Conditions in south of Chisapani Bridge in Geruwa River are suitable habitat for otter. This hypothesis is consistent with our data.  

   Human activities such as fishing, stone mining, habitat destruction in riparian zone and other human disturbances are causes of threats to otter. Fishing by local people are common practice  in park’s boundary. The use of methods particularly damaging to the fish population are prohibited by park authority, but methods like placing fish traps over small tributaries and the practice of damming and draining of small section of river are common practice.

   Acknowledgements: I am grateful to the sponsors who gave me financial support to carry out the study. I would like to thank Prof. Padma de Silva, Asian Co-coordinator, IUCN/SSC Otter Specialist Group for managing fund for this study. I would like to express my sincere gratitude to the International Otter Survival Fund provided fund for providing fund. Special thank goes to Mr. Prem Budha, Central Department of Zoology, Tribhuvan University who accompanied me in this study

   References

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   Hussain, S.A.1992.The wild otters of the Chamble  Sanctuary, Asia    XII,No.5:24-31. 

   Prater, S. H. 1993. The book of Indian Animal. Bombay Natural History Society. Oxford University Press. 

   Roberts,T. J.!997. The Mammals of Pakistan Oxford Univ. Press. 

   Shrestha, T.K. 1997. Mammals of Nepal. R. K. Printers, Kath., Nepal. 

   Suwal, R.N. 1995. Enumeration of the mammals of Nepal. Biodiversity Profiles Project publication no: 6.DNPWC, Kathmandu. 

   Tiler, C., M. Evans, C. Heardman and S. Houghton. 1989. Diet of smooth Indian Otter (Lutra perspicillata)  and of fish eating Birds: A field survey. JBNHS, vol.86 No.1, pp 65-70. 

   Umapathy, G.2000. Food Habits and activity patterns of the common otter Lutra lutra nair (F. Cuvier) at Pichavarum Tamilnadu,India. JBNHS, 97(3), pp367-369.