Interesting Creatures... The Olive Ridley Sea Turtle (Lepidochelys olivacea)

Interesting Creatures… The Olive Ridley Sea Turtle (Lepidochelys olivacea)

Aug 31, 2014 Features / Columnists, Interesting Creatures in Guyana

The Olive Ridley sea turtle (Lepidochelys olivacea), also known as the Pacific ridley sea turtle, is a medium-sized species of sea turtle found in warm and tropical waters, primarily in the Pacific and Indian Oceans.
The olive ridley is a small sea turtle, with an adult carapace length averaging 60 to 70 cm. The heart-shaped carapace is characterized by four pairs of pore-bearing infra-marginal scutes on myra rose chopra, six to eight counts ranging from five to nine plates on each side, with six to eight being most commonly observed.
Each side of the carapace has 12–14 marginal scutes. The carapace is flattened dorsally and highest anterior to the bridge. It has a medium–sized, broad head that appears triangular from above. The head’s concave sides are most obvious on the upper part of the short snout. It has paddle-like forelimbs, each having two anterior claws. The upperparts are greyish green to olive in colour, but sometimes appear reddish due to algae growing on the carapace. The bridge and hingeless plastron of an adult varies from greenish white in younger individuals to a creamy yellow in older specimens.
Hatchlings are dark grey with a pale yolk scar, but appear all black when wet. Carapace length ranges from 37 to 50 mm. A thin, white line borders the carapace, as well as the trailing edge of the fore and hind flippers. Both hatchlings and juveniles have serrated posterior marginal scutes, which become smooth with age. Juveniles also have three dorsal keels; the central longitudinal keel gives younger turtles a serrated profile, which remains until sexual maturity is reached.
Olive ridleys rarely weigh over 50 kg (110 lb). Hatchlings usually weigh between 12.0 and 23.3 g. Adults are somewhat sexually dimorphic. Mature males have longer and thicker tails, which are used for copulation, and the presence of enlarged and hooked claws on the males’ front flippers allow them to grasp the female carapace during copulation. Males also have longer, more tapered carapaces than females, which have round, dome-like carapaces.
Males also have more concave plastrons, believed to be another adaptation for mating. The plastrons of males may also be softer than females.
The olive ridley turtle has a circum-tropical distribution, living in tropical and warm waters of the Pacific and Indian Oceans from India, Arabia, Japan, and Micronesia south to southern Africa, Australia, and New Zealand.
In the Atlantic Ocean, it has been observed off the western coast of Africa and the coasts of northern Brazil, Suriname, Guyana, French Guiana, and Venezuela. Additionally, it has been recorded in the Caribbean Sea as far north as Puerto Rico. It is also found in the eastern Pacific Ocean from the Galapagos Islands and Chile north to the Gulf of California, and along the Pacific coast to at least Oregon. Migratory movements have been studied less intensely in olive ridleys than other species of marine turtles, but they are believed to use the coastal waters of over 80 countries.
Historically, this species has been widely regarded as the most abundant sea turtle in the world. More than one million olive ridleys were commercially harvested off the coasts of Mexico in 1968 alone.
But although they are considered the most abundant, globally they have declined by more than 30 per cent from historic levels. These turtles are considered endangered because of their few remaining nesting sites in the world.
They are however best known for their behaviour of synchronized nesting in mass numbers, termed arribadas. Although famed for their arribadas, many of the nesting grounds can only support relatively small to moderate-sized aggregations (about 1,000 nesting females). The overall contribution and importance of these nesting beaches to the population may be underestimated by the scientific community.
Aside from being subjected to contaminated environments in some areas, another threat to these turtles are power plants, which have documented juvenile and sub-adult turtles becoming entrained and entrapped within the saltwater cooling intake systems.
Most observations are typically within 15 km of mainland shores in protected, relatively shallow marine waters (22–55 m deep) as Olive ridleys are occasionally found in open waters.
The olive ridley is predominantly carnivorous, especially in immature stages of the life cycle. Animal prey consists of proto-chordates or invertebrates, which can be caught in shallow marine waters or estuarine habitats. Common prey items include jellyfish, tunicates, sea urchins, bryozoans, bivalves, snails, shrimp, crabs, rock lobsters, and sipunculid worms. Additionally, consumption of jellyfish and both adult fish (e.g. Sphoeroides) and fish eggs may be indicative of pelagic (open ocean) feeding. The olive ridley is also known to feed on filamentous algae in areas devoid of other food sources. Captive studies have indicated some level of cannibalistic behaviour in this species.
(Source: Wikipedia – The Free Online Encyclopedia)