Dermochelys coriacea (Leatherback Sea Turtle)

 

Zoological Profile, Taxonomy, and Marine Conservation of Dermochelys coriacea (Leatherback Sea Turtle)

The Leatherback Sea Turtle (Dermochelys coriacea), known in Sinhala as Dara Kesbawa (දරා කැස්බෑවා) or Thala Kesbawa (තලා කැස්බෑවා) and in Tamil as Ezhuthu Aamai (எழுத்து ஆமை) or Thozh Aamai (தோல் ஆமை), holds the distinction of being the largest of all living turtles and the fourth-heaviest modern reptile on Earth, behind only three species of large crocodilians.

Extremely distinct from all other marine turtles inhabiting Sri Lankan waters, Dermochelys coriacea is the sole surviving species within the genus Dermochelys and the ancient family Dermochelyidae. Unlike hard-shelled sea turtles, the Leatherback lacks a bony carapace and keratinous scutes, featuring instead a flexible, hydrodynamic shell composed of skin, oil-saturated tissue, and thousands of tiny embedded bony plates (osteoderms).

1. Taxonomy and Deep Evolutionary Lineage

While all other living marine turtles belong to the family Cheloniidae, the Leatherback belongs to its own distinct lineage, Dermochelyidae, which diverged from other sea turtles over 100 to 150 million years ago during the Cretaceous period.

• Kingdom: Animalia

• Phylum: Chordata

• Class: Reptilia

• Order: Testudines

• Suborder: Cryptodira

• Family: Dermochelyidae (Fitzinger, 1843)

• Genus: Dermochelys (Blainville, 1816)

• Species: Dermochelys coriacea (Vandelli, 1761)

Synonyms and Etymology

Commonly referred to historically as the lute turtle, leathery turtle, or luth, its scientific genus name Dermochelys translates from Greek to "skin turtle," referencing its unique dermal carapace architecture.

2. Anatomical Traits, Biometrics, and Physiological Adaptations

The physical structure of Dermochelys coriacea represents an evolutionary apex of marine hydrodynamics and deep-diving specialization.

Key Biometrics and Hydrodynamics

• Total Body Mass: Adult Leatherbacks average between 250 kg to 700 kg (550 to 1,540 lbs), with record specimens exceeding 900 kg (nearly 2,000 lbs).

• Carapace Length: Curvilinear Carapace Length (CCL) ranges from 1.3 to 1.8 meters (4.2 to 6 feet) in adult individuals.

• Carapace Architecture: The teardrop-shaped carapace features seven distinct longitudinal ridges (keels) running from anterior to posterior, significantly reducing drag in open-ocean currents.

• Flipper Span: Possesses the largest paddle-like front flippers relative to body size among all sea turtles, often expanding up to 2.7 meters (9 feet) from tip to tip.

Specialized Physiological Adaptations

1. Gigantothermy & Endothermic Capability: Unlike typical cold-blooded reptiles, Leatherbacks can maintain a core body temperature up to 18°C (32°F) above surrounding water temperatures. Their massive body volume, thick layer of oily insulating sub-dermal fat, and countercurrent heat-exchange circulatory systems allow them to forage in sub-freezing polar and sub-Arctic waters.

2. Deep-Diving Biology: Capable of diving to depths exceeding 1,200 meters (4,000 feet)—deeper than any other reptile and matching deep-diving marine mammals. Their flexible shell and collapsible lungs prevent decompression sickness under extreme hydrostatic pressure.

3. Esophageal Papillae: The mouth and esophagus are lined with hundreds of stiff, backward-pointing, conical spines called esophageal papillae. These structures prevent slippery jellyfish from escaping while the turtle expels swallowed seawater prior to ingestion.

3. Sri Lankan Sea Turtle Species Comparison

Sri Lanka's coastal waters host 5 of the world's 7 sea turtle species. The Leatherback is easily distinguished from the other four sympatric species found along the island's coastline.

Morphological Feature	Leatherback (D. coriacea)	Green Turtle (Chelonia mydas)	Hawksbill (Eretmochelys imbricata)	Olive Ridley (Lepidochelys olivacea)	Loggerhead (Caretta caretta)
Local Sinhala Name	Dara / Thala Kesbawa	Gal Kesbawa	Pothu Kesbawa	Batu Kesbawa	Olugedhi Kesbawa
Average Adult Weight	300 – 700+ kg (Largest)	110 – 190 kg	45 – 80 kg	35 – 50 kg (Smallest)	80 – 160 kg
Carapace Type	Leathery skin with 7 ridges	Hard bony scutes (4 lateral)	Overlapping serrated scutes	Hard bony scutes (6-9 lateral)	Hard bony scutes (5 lateral)
Primary Diet	Gelatinous Zooplankton (Jellyfish)	Seagrasses & Algae	Sea Sponges & Coral	Crabs, Mollusks, Shrimp	Hard-shelled Crustaceans
Nesting Frequency in SL	Extremely Rare / Critical	Most Common	Rare / Threatened	Fairly Common	Rare

4. Geographic Distribution and Nesting Strongholds in Sri Lanka

The Leatherback is a circumglobal pelagic species, undertaking trans-oceanic migrations across the Atlantic, Pacific, and Indian Oceans.

• Pelagic Migration: They spend the vast majority of their lives in the open ocean, traveling thousands of kilometers between deep-water foraging zones and tropical nesting beaches.

• Nesting Distribution in Sri Lanka: While rare compared to Green and Olive Ridley turtles, Leatherbacks nest on select soft, undisturbed sandy beaches in southern and southeastern Sri Lanka:

  • Rekawa Sanctuary (Tangalle): One of the primary monitored nesting sanctuaries where female Leatherbacks periodically emerge.

  • Godabaya (Hambantota): Historically recognized as a major Leatherback nesting hotspot in Asia, though nesting frequency has drastically declined.

  • Kosgoda and Bentota: Occasional nesting reports recorded along the southwestern coastal belt.

5. Foraging Ecology and The Ocean Plastic Threat

Dermochelys coriacea is an obligate gelatinous zooplankton feeder (gelatinivore). Its diet consists almost exclusively of jellyfish, pyrosomes, salps, and siphonophores. To meet its massive energetic demands, an adult Leatherback must consume its own body weight in jellyfish every day (up to 730 kg of jellyfish per day).

The Critical Plastic Threat

Because Leatherbacks hunt visually from below—looking upward at floating translucent jellyfish shapes against the surface light—they frequently mistake floating plastic bags, discarded food wrappers, and clear synthetic marine debris for jellyfish. Ingesting a single plastic bag can obstruct the digestive tract, lock their backward-facing esophageal papillae, cause starvation, and lead to mortality.

6. Reproductive Biology and Nesting Mechanics

• Sexual Maturity: Estimated to reach maturity between 15 to 25 years of age.

• Nesting Behavior: Females return to their natal beaches to nest at night. Because of their immense weight and lack of sharp claws, they require wide, open beaches with deep sand approaches free from rocky reef barriers.

• Clutch Size & Nest Architecture:

  • Digs massive nest pits up to 1 meter deep.

  • Lays a typical clutch of 60 to 90 large, nutrient-rich fertile eggs, followed by 20 to 40 smaller, yolkless "dummy" eggs that act as a thermal buffer and prevent sand from suffocating the viable eggs.

• Incubation & Sex Determination: Incubation takes roughly 60 to 70 days. Like all sea turtles, sex is determined by nest temperature (Temperature-dependent Sex Determination - TSD), where warmer sand temperatures produce females and cooler temperatures produce males.

7. Conservation Status, FFPO Protections, and Human Impact

IUCN and National Red List Status

• Global IUCN Red List Status: Classified as Vulnerable (VU) globally, but specific regional sub-populations (such as the Southwest Indian Ocean and West Pacific populations) are classified as Critically Endangered (CR) due to population collapses exceeding 80%.

• Sri Lanka National Status: Listed as Critically Endangered (CR) within national wildlife red data assessments.

Anthropogenic Pressures

1. Commercial Bycatch: Entanglement in longline fisheries, offshore drift gillnets, and bottom trawlers represents the leading cause of adult mortality in the Indian Ocean.

2. Coastal Development & Light Pollution: Artificial lights from coastal hotels and roads disorient emerging hatchlings, causing them to crawl inland away from the ocean.

3. Historical Egg Poaching: Illegal harvesting of eggs from unmonitored beaches outside protected marine reserves.

Legal Protection in Sri Lanka

Under Schedule III of Sri Lanka’s Fauna and Flora Protection Ordinance (FFPO), Dermochelys coriacea is a strictly protected species. Killing, injuring, capturing, possessing, selling turtle products (carapace oil or meat), or disturbing nests and collecting eggs carries severe penalties, including non-bailable fines and imprisonment.