© Howard Martenstyn

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Hawksbill Turtle

Marine Reptiles

Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, being descended from four-limbed ancestors. The earliest known reptiles originated around 315 million years ago, having evolved from advanced reptile-like amphibians.

 

Today, three living reptile subgroups are recognised in Sri Lanka's marine enviroments:

  • Testudines: sea turtles - 5 species

  • Squamata:  sea snakes - 16 species

  • Crocodilia:  crocodiles - 1 species

For more online information on Sri Lanka's amazing reptiles see:

Further reading:

  • 'Sea Snake Toxinology' by P. Gopalakrishnakone.

  • 'An Overview of Sri Lankan Sea Snakes with an Annotated Checklist and a Fileld Guide' by Ruchira Somaweera and Nilusha Somaweera

Sea Turtles

 

Five out of the seven species found in the world are native to Sri Lanka. Kemp’s ridley is found only in the Atlantic Ocean and the flatback turtle is found only in Australia and surrounding seas. Nesting in Sri Lanka occurs throughout the year. March to May is considered the high season with a peak in April.

 

Most of the coastline beaches south of Colombo and around the south to Arugam Bay in the East are well known nesting grounds for sea turtles. They are found at sea all around in Sri Lankan waters. Sea grass beds and coral reefs are important foraging grounds.

 

Conservation

Under the Fauna and Flora Protection Ordinance in 1938 and amended in 1972, it is an offence to capture, kill, injure or posses sea turtles or their eggs. Furthermore, All five species of turtles are strictly protected by the Fauna and Flora Protection (Amendment) Act No. 22 of 2009. They are all included in the IUCN Red List of Threatened Animals and listed under CITES Appendix I (most endangered).

Threats

 

  • Plastics are easily mistaken for their favourite foods. Plastic shopping bags look like jellyfish to turtles so please be careful that the bags don't get into the rivers or the sea. Many plastic bags have become stuck in sea turtle intestinal tracts causing serious health problems and death.

  • Poaching for eggs and meat.

  • Conflict with fishermen, fishing line and net entanglement.

  • Vessel strikes.

  • Habitat destruction due to human development of nesting areas such as beach-front construction, land "reclamation" and increased tourism. This includes beach erosion, beach activities and artificial lighting.

  • Pollution: Chemical pollution may create tumours; effluent from harbours near nesting sites may create disturbances; and light pollution may disorient hatchlings.

  • Nest and hatchling predation on land by ants, feral dogs, wild boar, jackals, mongoose, water monitors, crabs, raptors and seabirds.

 
Discovering Sea Turtles

 

Sea turtles, sometimes called marine turtles, are air-breathing reptiles that inhabit the tropical and sub-tropical oceans of the world. They belong to the order of Testudines and represent an ancient and distinct radiation of reptiles that appeared more than 100 million years ago. There are seven species of sea turtles living in the world representing two families, Cheloniidae and Dermochelyidae. These are the only extant families of marine turtles descending from a large diverse marine radiation of cryptodiran turtles.

 

Cheloniidae is characterised by an extensively roofed skull with well-developed rhamphothecae while Dermochelyidae is characterised by the extreme reduction of bones of the carapace, plastron and the neomorphic epithecal shell layer consisting of a mosaic of thousands of small polygonal bones (Prichard 1997).

Why Protect Sea Turtles

 

Sea turtles play key roles in supporting ecosystems in the ocean as well as on land. Besides being a source of protein and nourishment to well being of wildlife at sea as well as on the beaches there are other benefits to ecostems.

 

  • Sea turtles and dugongs act as grazing animals that constantly cut the grass short and help seagrass beds spread across the sea floor. Sea grass beds provide breeding grounds for numerous species of fish, shellfish and crustaceans. Without sea grass beds, many marine species harvested by fishermen would be lost, as would the lower levels of the food chain. This could result in many more marine species eventually becoming endangered or extinct.

  • Sea turtles have been found to support healthy reefs by controlling sponges which would otherwise out-compete reef-building corals for space.

  • Dune and beach vegetation are nourished and grow healthier and stronger as a result of nutrients from egg shells, unhatched eggs, trapped hatchings and carcasses. Healthy vegetation with strong root systems prevents beach erosion.

Life Cycle

 

The sea turtles' life cycle starts when a female lays its eggs on a nesting beach. From six weeks to two months later, hatchings make their way to the surface and quickly heads to the sea and then swims out to the open ocean. It may take up to ten years before juveniles return to inshore waters to forage. 

 

It may take decades (varies by species), for sea turtles to reach sexual maturity. Once they reach sexual maturity they may migrate thousands of kilometers to reach breeding grounds. After mating at sea, adult female sea turtles return to land to lay their eggs. They will come ashore to lay eggs, generally in the area where they were born. Most species will nest several times during a nesting season and every 2-4 years in maturity over the course of their lifetime.

 

It is not known exactly how long sea turtles live in the wild, but scientists think their life span may be as long as a century.

Be AWARE! Plastics of any kind that make their way out to sea will finally disintegrate and be consumed by turtles and other marine life that will never ever digest in their stomachs.

Sea Turtle Species
Family: Cheloniidae
Family: Dermochelyidae
Turtle Watching

 

Turtle watching involves some waiting and some walking on the beach because as with all of nature, it is the turtle (not us) that sets the time and place of the event! The whole process of a nesting turtle can take up to 3 hours and can include ‘false crawls' (non-nesting emergence). A female turtle can only be approached once she starts laying eggs because by then she is engaged in a very mechanical, almost trance-like behavior and it is unlikely for her to be frightened by spectators.

 

Of course there is no guarantee that turtles come to nest every night, but sitting on a deserted beach under the open starry Sri Lankan sky is an incredible experience in itself.

 

At sea, turtles can rest or sleep underwater for several hours at a time but must surface to breathe. This provides an opportunity to see them when they surface for a breath and if lucky may rest for brief periods and even bask at the surface.

Turtle Nesting Sites

 

Sea turtle nesting locations stretch from Pottuvil on the east coast, along the southern coastline through to Mount Lavinia just south of Colombo. Rekawa beach was declared a sea turtle sanctuary in 2006 and is known to have the largest rookery in Sri Lanka. The second largest rookery is in Kosgoda where five species are known to nest. Although there are several sightings, strandings, catch and bycatch of turtles off the Kalpitiya peninsula there are hardly any records of nesting.

 
Sea Snakes

 

Sea snakes belong to the Elapidae family of highly venomous snakes. They mainly inhabit coastal marine environments for most of their lives. Although they are mostly known to be non aggressive towards humans, few unprovoked incidents have been recorded. The beaked sea snake (Enhydrina schistosa), Stoke's sea snake (Astrotia stokesii) and ornate sea snake (Hydrophis ornatus) tend to be more aggressive and may bite humans unprovoked.

Antivenom administration is indicated for any patient with signs of envenomation. The agent of choice is polyvalent sea snake antivenom. We do not have sea snake antivenom and the available land snake antivenom is not effective for sea snake envenomation.

Ceylon Medical Journal 2012; 57: 174

Be AWARE! Stay well clear from sea snakes and any attempt to kill them is not worth the risk if you have not got bitten.

 

Sea snakes are well adapted to aquatic life so most of them have flattened streamlined bodies. They can remain underwater for several hours and some are capable of extracting oxygen that is dissolved in the water. One intriguing adaptation is that sea snakes can remove nitrogen through their skin while diving which prevent nitrogen bubbles forming in their body.

 

They are charaterised by a paddle-like flattened tail, muscular flap in their nostrils, a single lung that extends within its body, bent beak-like rostrum, and receptors which can sense changes in salinity. There are two immovable fangs at the back of the upper jaw.

Currently, sixteen species of sea snakes have been recognised in Sri Lankan waters, mostly in the Gulf of Mannar. They range in length from 75 cm to the 3 m narrow-banded sea snake, which is probably the longest sea snake in the world. Accurate identification of sea snakes to the species level is very difficult, especially if dealing with live animals. Most species (especially Hydrophis species) show wide interspecific variation which makes it difficult to exclusively use external characters for identification.

Legend: In the species table below

* indicates species or subspecies taxonomy not fully elucidated.

# indicates presence in Sri Lankan waters unconfirmed.

Threats

 

  • Humans wanting to kill them on sight.

  • Conflict with fishermen and net entanglement.

  • Habitat destruction (coral reefs and mangroves).

 

Compared to terrestrial reptiles, sea snakes are not under any severe threats in Sri Lanka.

Conservation

 

There is no effort on sea snake conservation in Sri Lanka. This may be due to the lack of knowledge about them and their habits. Sea snakes are not listed as “protected” in the Fauna and Flora Protection Act (FFPA) of Sri Lanka and are also not listed by Convention on International Trade of Endangered Species (CITES). 

Why Protect Sea Snakes

 

Unfortunately their importance for maintaining a healthy ecosystem in balance is not well understood and are mostly killed when encountered.

Sea Snake Species
Family: Elapidae
Crocodiles
 
Mugger crocodile
Crocodylus palustris
Saltwater crocodile
Crocodylus porosus

There are two breeding species of crocodiles in Sri Lanka. The saltwater crocodile, Crocodylus porosus, is the largest of all living reptiles and the most aggressive crocodile species. An adult body length ranges from 4.5-5.5m and weighs over 1,000 kg. It is also the most widely distributed crocodile species as it can travel long distances by sea and colonize new locations. Males are strictly territorial and solitary, unlike the mugger crocodile, Crocodylus palustris, which normally occur and bask in groups. Although the mugger is unlikely to be found in marine environments, their habitats can overlap due to the wide distribution of saltwater crocodiles. 

Distinguishing between saltwater & mugger crocodiles

Saltwater crocodile

 

  • Dorsal osteoderms are ellipsoid, and separated from one another by epidermis.

  • Neck is wider than the head.

  • Snout is tapered and elongate.

  • Neck is normally covered with indistinct granular scales.

  • Dorsally brassy yellow in colour, spotted and blotched with irregular transverse dark bands. Adults become a dark dull green, the head and jaws yellowish, and densely speckled with black.

Marsh crocodile

 

  • Dorsal osteoderms are rectangular and aligned to form transverse rows.

  • Head is usually wider than neck

  • Snout is relatively short but wide.

  • Neck has a set of 4 large scales and a few indistinct scales.

  • Dorsally dark olive green to greyish in colour, sometimes having darker bands and spots on the tail. There are large scales on the sides of the body.

Discovering Crocodiles

 

Crocodiles are large aquatic animals and are classified as a biological subfamily Crocodylus. A total of 14 extant species have been recognized in the world. They first appeared on earth 240 million years ago and can live for up to 80 years.

 

Each crocodile jaw has 20-24 teeth that are meant to grasp and crush, not chew. Crocodiles are able to replace each of their teeth up to 50 times in their lifespan.

 

Crocodiles mainly inhabit estuarine deltas in coastal areas and may sometimes travel long distances up river particularly during the dry season.

Threats

 

  • Poaching.

  • Conflict with fishermen and net entanglement.

  • Habitat destruction (polluted drainage, deforestation, landfill, and land use conversions).

  • Nest and hatchling predation by land monitors, dogs and birds.

Conservation

 

Both species of crocodiles are strictly protected by the Fauna and Flora Protection (Amendment) Act No. 22 of 2009.

Crocodile Safety

 

Be CROCWISE!

While crocodiles may be more active during the wet season, it should never be assumed that it is safe to enter the water where crocodiles may be present at any time of the year. They are potentially dangerous to humans. Marsh crocodiles have been known to vary in their temperament, from being ferocious to allowing people to bathe in their abode. On the other hand the saltwater crocodile is usually a man-eater. Fortunately, crocodile attacks are not spontaneous but rather calculated.

 

Some of the ways to stay safe in areas that may have saltwater crocodiles include:

  • Be crocwise in areas where crocodiles may be present even though there is no warning sign.

  • Check with area residents for presence of crocodiles.

  • Only bathe in Crocodile Excluding Enclosures (CEEs).

  • Always be vigilant for crocodiles particularly at night and during the breeding season.

  • Never provoke, harass or interfere with crocodiles, even small ones.

  • Never feed crocodiles!

  • Avoid approaching the edge of the water and don’t paddle or wade at the waters edge.

  • Stay well away from crocodile slide tracks. Crocodiles may be near by.

  • Always stand a minimum of 5m from the water’s edge when fishing.

  • Be especially vigilant when launching or landing your boat.

  • Do not lean over the edge of a boat or dangle your arms or legs over the side of a boat.

Be AWARE! 

 

Saltwater crocodiles are "sea going" animals.

 

Saltwater crocodiles are found at sea for several reasons:

  • They get washed out to sea from rivers during the rainy seasons due to strong currents.

  • They travel by sea to circumvent travelling longer distances by land.

  • They may get disorientated and are found many kilometres from land.

  • They are known to use open ocean currents to travel large distances and may spend weeks at sea.

Why Protect Crocodiles

 

Crocodiles play an important role in maintaining the productivity and diversity of wetland ecosystems on which people depend. The presence of crocodiles in a river actually increase the yield of fish. They eat ailing fish in a significant higher proportion than healthy fish, thus improving the common health of the fish stock. By preying on the most common fish, crocodiles balance the fish population; any species which suddenly becomes dominant is rebalanced. Crocodile droppings are nutritious for fish and contain critically important chemicals.

Crocodile Watching

Convenient locations for observing saltwater crocodiles include: Mahaweli ganga, Verugal river and Kumana on the east coast, Yala, Bundala and Nilwala ganga in the south, and Bentota river and Muthurajawela Wetlands near Negombo on the west coast.

 
Crocodile Species
Family: Crocodylidae
Mating Green Turtles

© Howard Martenstyn