Saturday, August 18, 2012

Otter - Swimming legend in the wild

Swimming took a lot of shine at the Olympics 2012 in London, with Michael Phelps, becoming the most decorated Olympian in history. Competitive swimmers train hard and develop their bodies, for competition, while the greatest swimmer in the natural world - the otter, does so for its very survival and appears to do so with pride and joy. ZooLander this week reports on the otter in the Dehiwala Zoo...

There is a well known sports club in Colombo named ‘Otters’, which has taken its name after these delightful creatures of the water and master swimmers, making known the clubs special affiliation to swimming. The agile otters are famous for an amazing ability to conquer the river habitats in Sri Lanka. In the wild, it is difficult to observe otters at a close range, as they are naturally shy; yet they are some of the most charismatic  animals you can find in the zoo, where you can observe them closely, and photograph their antics, in captivity.

30-1The Otter family has 13  species with 5 otter species recorded in Asia. The species found in Sri Lanka is called the Eurasian Otter (Lutra lutra). As the name indicates a European part, it might convey that this species is found m0re prevalently   in Europe, which is not the case, but is very widely distributed. They are also known as the Common Otter and Old World Otter. The Eurasian Otter is also tagged as the least social animal.
Otters are semi-aquatic; and lives both in water and land. Otters are usually solitary and relatively  nocturnal. When not fishing, they like to sleep.

Master swimmer
Though clumsy when walking on land, the body of the otter is well designed for an aquatic lifestyle. This swimmer and diver, moves in water by strong undulations of its body and tail and strokes of its hind feet. While human divers use artificial fins, the otter’s feet are webbed in a manner which gives it power to push the water more efficiently. (Webbed feet are common in ducks)The Otter can close its nostrils and ears, when in water, so there is no issue about water going in from these body holes.

Its body shape helps the otter to reduce the water resistance when it swims and maintain the speed. Its fur is short and dense and keeps the skin dry by trapping a layer of air around the body. Unlike other marine mammals, otters don’t have blubber and rely on thick fur to keep warm, but this double coat also helps them to keep afloat. It is mentioned that the bubbles of air trapped in their fur give them  a silvery appearance underwater. The Eurasian otter’s nose is about the smallest compared with the otter species and has a characteristic shape, described as a shallow ‘W’. The strong whiskers on their face are believed to be used for locating prey.

Fishing for a living
The otter’s staple diet is fish. But it also doesn’t mind some unwary frog or occasional water bird. Some studies show that otters have a preference for eels. Being opportunistic feeders, otters do not show preferences for one fish species over another. They will feed on in relation to their locale and seasonal availability. Otters can give a high speed chase to catch a fish, unlike many other animals that silently wait and ambush when the prey  swims towards them.

Otters in the wild catch and feed predominantly on live animals; there are only a few recorded instances where it was found to have eaten dead fish. While that is the case in the natural world, the otters in the Zoo have to depend upon the dead fish provided by their keepers. If you visit during an evening, you may also be able to witness the zoo’s otters getting a feast of fish to dine on. Their average daily consumption of food in captivity is about 1.5 kg per day.

Blind babies
Otters live in burrows on the banks of waterways called Holts. These are usually only accessible from underwater, hence very successful at keeping out the land based predators and gives protection to their babies.

The main mating season is from February to March and July. After a gestation period around 60 to 70 days, the females give birth to a litter of usually 2-3 cubs, each weighing about 100-120g. Baby otters are born blind; will open their eyes after one month; will leave the nest at around two months; and are weaned by 3 months. The young stay around their mothers for up to 14 months and reach sexual maturity at 2 or 3 years. It is mentioned that an otter has a lifespan of 10-12 years.

Sea going cousin
Our otter species which live in river ecosystems have a few cousins that live in the sea. The sea otters inhabit offshore environments, where it dives to the sea floor to forage. The otters are just as happy in salt water as they are in fresh water, often diving down 20 metres and for up to two minutes at a time, although records show that otters can go as deep as sixty or seventy metres and stay under for up to four minutes. They must, however, have access to fresh water to clean themselves with, as the salt water clogs up their fur and inhibits insulation.

The Sea Otters prey  mostly on marine invertebrates such as sea urchins, various molluscs and crustaceans, and some species of fish. They develop special techniques to open up tightly  shut shells. First, it uses rocks to dislodge prey and to open shells making it one of the few mammal species to use tools - indicative of how brainy the otter can be.

Near threatened
Eurasian Otters had been a common species decades ago, now their populations are declining all over the world. The IUCN which publishes the Red List of Threatened Fauna and Flora indicates that many local populations of otters have become extinct.  In their list it is stated that water pollution as the major threat to Eurasian Otters, mentioning that water pollution in fact has caused recent local extinctions from which Western European populations are only  now recovering as a result of environmental improvements and focussed conservation efforts.

The IUCN says agrochemicals such as DDT or Mercury affect the otter physiology directly. Pollution also reduces their food supply  due to nitrate-induced eutrophication from agricultural run-off and untreated sewage, and acidification from atmospheric pollutants. Oil spills threaten coastal populations. In parts of the range, illegal hunting is a major issue, and the rise of fish farming has led to conflict, resulting in some countries in licenses to kill otters being issued by authorities. Road traffic accidents too have been recorded commonly when the otters are trying to move from different parts of habitats.

Conservation actions
Artificial otter Holts are a good way of encouraging breeding among wild otters by providing them with a ready-made safe place to bring up their young.Conservation actions have helped Eurasian Otters to show some signs of recovery, and to halt being classified under extinct.

Otters were once common in Sri Lanka too. But habitat loss and pollution have contributed to a decline in their wild populations. So, whenever you visit the zoo and see the otters, think, it is another animal that has been pushed to the limits of extinction due to human activities and that we should be mindful when engaging in development activity and do so carefully without compromising the natural world.

http://www.lakbimanews.lk/index.php?option=com_content&view=article&id=6527:otter-swimming-legend-in-the-wild&catid=41:mag&Itemid=12

No comments:

Post a Comment