A recce survey of Smooth-coated otters (L.p.perspicillata)
in the estuaries of Muthupet, Tamil Nadu
photo: Dipani Sutaria
Sutaria,D., and V.Balaji., 2013. A recce survey of Smooth-coated otters (L. p. perspicillata) in the estuaries of Muthupet,Tamil Nadu. OMCAR Foundation. Tamil Nadu, India.
Three species of otter are found in India, the Indian smooth - coated otter, Lutrogale perspicillata perspicillata; the Eurasian otter, Lutra lutra and the Asian small - clawed otter, Aonyx cinerea. Otters are considered bio – indicators of their aquatic ecosystems. In some locations, Otters are caught and trained to help in fishing ( ie. Sunderbans). Smooth - coated otters occupy estuarine waters and coastal stretches, and are prone to the large –scale development in our rivers and along the coasts. Around the world Otters face the major threats of habitat deterioration, habitat loss and poaching for otter pelts. Information on distributions, space use, behavioral ecology and population size are non-- existent, making it difficult to assess how changes in the ecosystem may be affecting their survival.
To assess the presence and distribution of otters and otter dens in the Muthupet region of Thanjavur, Tamil Nadu.
1. Verify the location and species of otter found in the study area
2. Obtain perceptions towards Otters from local fishers
3. Verify the presence of otters in close – by water channels.
OMCAR foundation’s project coordinator Anbu met me at the train station in Thiruvarur and was so very kind to arrange for me to stay at his family friend’s place in his village Vadiyakkadu. Vadiyakkadu is about 2 hours from Thiruvarur and an hour northeast of Muthupet lagoon. After arrival and a quick and delicious meal, we set out to the location where Anbu’s uncle had earlier seen an Otter den along a water channel. On day we went to two other locations from where otters had been reported. The details of these locations are given below and in Figure 1:
We went to an active otter den approximately 50m from a tar by road, at Thillaivilagam village. Observing the den from across the channel, its structure caught our attention –a very functional structure. The den was under a Prosopis juliflora amongst the thick maze of Eichhornia, water hyacinth stems. Water hyacinth was very dominant in the channel on both sides of the channel (an indicator of freshwater). The den had three openings. One opening was about a foot above the surface of the water, easy for the Otter to get into the safety of the water and easy to come back in. The other two openings were about a meter above these and on either side of a P. juliflora. One of these openings had plenty of fresh spraint outside it (Figure 3), while the other had plenty of empty molluscan shells outside it.
We stayed at the den from 3:30pm to 7pm and heard the otters calling out around 5pm. Two Smooth--‐coated otters (L.p.perspicillata ) came out around 6pm, and we followed their trail in the water till one of them raised its head above the water hyacinth. There are two water tanks on the same side of the bank as the den. There were also two houses on either side of the den, and while there are no fishers in this section of the channel, people from the houses use the channel for household purposes. The riparian vegetation is primarily Prosopis juliflora. Talking to the people from the houses, we found out that there was no conflict with the otters. They sighted otters almost every day and often sighted them playing on the opposite bank. They said they had also mongoose, also called Keeripilai in Tamil. The location is about 12km upstream from the mouth to the sea. A walk along the side of the channel exposed another latrine location about 100m away from the den we saw. N 10.40953 E 79.57867.
On March 6th 2013, we visited the freshwater aquaculture ponds in Idubavanam. The location is apprx 15km upstream from the sea mouth. One of the owners, Sri Jeevanandam spoke with us at length. He has been doing aquaculture in this location for the last 15 years and has ten ponds of one acre each on his land. He told us that 5--‐10 otters had started raiding his ponds only in the last 2--‐3 years, after 6pm, mainly only during the summer months. He presumes that during the rains they stay in the tributary about 1km northwest of the ponds. He said he had only seen adults, never seen pups or any dens. He said that the Otters caused huge damages earlier, when he would get only 10--‐12 fish after releasing 100gms of fish roe. After hiring a full time security personal to keep vigil, the otter raiding had reduced by a large degree, but the otters still visited every night in the summer months. The main fish species being reared are Catla catla, Labeo rohita, Cirrhinus rigula, Hyphthalmichthys molitrix, Ctenopharyngodon idella, Cyprinus carpio species, Channa species, and Lates calcifer. The vegetation along the edges of the ponds is mainly a native grass species which grows tall and thick (not identified), along with coconut trees and guava trees. On its western edge, the ponds are separated from paddy fields by a tar road.
On the other three sides there are paddy fields, with patches of forest, till a river channel a kilometer east of the ponds. N 10.42857 E 79.59039
Otters have also been reported from a river channel next to village Thondiyakkadu. The riparian vegetation is mainly Prosopis juliflora, Calotropis gigantia, and tall grass (not identified) along the water. Water hyacinth is present in the channel only after the rains or after the dam has released water. The location is approx. 10km upstream from the sea mouth and adult otters, pups and dens have been recorded from here. The main fish they catch here are Catla, Rohu, Kudova, Kurial, Kenti and Veerameen, of which the last three are most favoured by otters. We visited the village on day 2 and spoke to four fishermen, who fish in the river.
The village has around 15 fishers who fish in the river, the rest do marine fishing. N 10.38967 E 79 58204 Interviewee 1: Sri Sellappan (age: 50 years) has been fishing here all his life. He said that otter numbers have increased in this channel only in the past 5 years. He has the dual occupation of fishing and agriculture. He fixes a gill net across the channel and leaves it overnight. He often see’s otters swimming in the water, trying to catch fish from such nets, often damaging the net. He said that he has no problems with the otter if only it did not damage the net. He said that otters also chase fish into the net. He has seen solitary animals and also seen large groups of 20--‐30 otters. In the last year though, freshwater flow has reduced, as the monsoon was very bad and the flow from the Cauvery dam was minimal. Due to the absence of freshwater and freshwater fish, the otters too are not as abundant as before. He said he has never caught an otter and would not want to hurt the otters. Interviewee 2: Sri Thangaraja (age: 51 years) is the head of the fishing community here.
He has been fishing regularly here for the past 18 years. He said that 10 years ago the sighting numbers were low, probably one or two per season. The number of otters has increased in the past 10 years. He said they see otters mainly while fishing in the channels using fixed gill nets that are left overnight (8pm to 4am). He said he has seen groups of one, two and a maximum of ten otters at a time and that he has also seen pups. He said he likes otters except while fishing. In which case, he gets very irritated and angry because the damage to nets is of 500Rs/2 months for him. He says the water in this channel rises only if the dam releases water, which it has not in the last year. This is the reason sightings of otters are few this year.
Sri Raja (age: 37 years) also has a dual occupation of fishing in the river and agriculture. He uses a large mesh size gill net across the channel from 8pm to 5am. The sightings and encounters with Otters have increased in the past ten years, and is most common after July when the channel has freshwater. He has seen them on land and in water. On land they travel in a row and he said he has seen pups too. He said that otters are not scared of them, but are scared of light and sound. He said the otters caused him 5000/yr of damage, which is why he didn’t like them. He mentioned that otters do not damage the other type of traditional fixed trap gear (pound net or stake net), also across channel and left overnight.
Sri Rajamani (age: 69years) usually fishes in his free time in the channel. Otherwise his occupation is agriculture. He uses the stake/pound net in the channel and leaves in overnight. It is called ‘saatt net’. He usually checks the traps every morning and just leaves the net fixed otherwise. His fishing is not disturbed by otters nor is there any damage to the gear by otters. He has seen Otters in this river channel and the one parallel to it for decade. His last sighting was in March 1st week in the other channel. He has seen a maximum of ten animals in a group, has also seen pups here, in fact he has seen pups every often but has not seen a den. He says the number of encounters have increased recently, especially in the last ten years.
Yeen Ten Hwang and Serge Larivière, 2005. Lutrogale perspicillata, Mammalian Species, American Society of Mammologists, No. 786, pp. 1–4, 3 figs
Figure 1.Den at location 1
Figure 2: Otter at location 1
Figure 3: Spraint or latrine site
Figure 1. a) Map showing the region of Muthupet in Tamil Nadu, India; b) Locations where the current survey was carried out.
(using systematic sampling for sighting surveys and interviews)
1) What is the distribution and density of otter dens (active and inactive dens of different species of otter) in the Point Calimere (Nagappattinam)– Muthupet (Thanjavur) region of Tamil Nadu?
2) Has the density and distribution of otters and otter dens changed over time and what are the biological/environmental and anthropological factors that influence these changes?
3) What are the habitat and prey preferences of Otters in the region?
4) What is the population structure and social structure of otter groups found in the same tributary or channel? (might require lab based analysis)
5) Compare the three case studies presented here (gill netters, stake netters, aquaculture ponds) to formulate conservation strategies and to investigate behavior, space use and activity patterns of otters.
6) Characterize the interactions between humans and otters in the study area. Is there an overlap over space and time, between otter and human activities in the study area?
7) Identify strategies to mitigate negative interactions between humans and otters (some locally designed methods to keep otters away from gill nets?)
8) Motivate locals to protect dens close to their home, by showing them the ecological importance of otters and their conservation value.
Long--‐term conservation measures:
It would work wonders if the local people would naturally want to protect the otters, as indicators of fish presence, freshwater, and ecosystem health. The protection and non—disturbance of dens and pups is very vital. People living lose to dens can form a community network of otter protectors and can work together to think of logical solutions for conflicts between humans and otters. Since the conflict between otters and people in Muthupet is limited to the damage of gill nets or raiding of ponds, energies could focus on how to mitigate or avoid this conflict. Local strategies can be used to keep otters away from gill nets since they seem to be scared of light and sound; or more people could be motivated to use the otter friendly stake net J; and finally it is important to maintain, the natural vegetation along water banks, and the health of the riverine ecosystem and its fish abundance and diversity. Discussions about these amongst the community network will bring long term and effectual conservation of otters in Muthupet.
Am very thankful to OMCAR for organizing this trip and and villagers of Vadiakkadu for all the hospitality extended by them.
*Dipani is an independent ecologist based in Ahmedabad, Gujarat and is affiliated to James Cook University, Australia from where she completed her PhD, studying Irrawaddy dolphins in Chilika Lagoon, India. Dipani comes from a zoology and environmental science background and has channeled her energies into marine and estuarine systems. Her current research activities cover human-animal interactions; marine and aquatic mammals; animal behavior; urban biodiversity assessments and sustainable development practices. She works with local researchers, institutions and NGO's at different project locations, and can be contacted at Dipani.Sutaria (at the rate of) gmail.com