Monday, 9 February 2015

So you think you know your turtles?

 Historically the Cayman Islands had four out of the world’s seven species of turtle nesting around its coastline: the green turtle (Chelonia mydas), the loggerhead turtle (Caretta caretta), the hawksbill turtle (Eretmochelys imbricata) and the leatherback turtle (Dermochelys coriacea). Today only the first three nest on our beaches. But can you tell the difference between our three remaining species?

No? Well let us see if we can sort that out for you!

First to the stage – the green turtle (Chelonia mydas):
Length: Can grow to an average size of 1.5m (5ft)
Weight: Can weigh up to 317.5kg (700lb)
Description: Green turtles are named for the unusual green fat that resides under their carapace and are found in shallow tropical and subtropical coastal waters. They have a dorsoventrally flattened body (a body that is flattened from top to bottom like a pancake) that is covered by a tear-drop shaped carapace with a scute pattern of 4,5,4. “Scutes” are the plates on a turtle’s shell. Green turtle shells have 4 scutes along each side and 5 scutes down the middle (see the diagram below). The carapace is coloured with flecks of green, brown, white and gold which gives it a mottled effect underwater. Unlike the other three species found here, the green turtle has a small unhooked beaked head at the end of a short neck.
Diet: They feed mostly on a variety of seagrasses.
Track pattern: When females crawl on to the beach, their tracks are very large and symmetrical in pattern. This is because female green turtles move their front flippers at the same time when crawling on the beach (like swimming the breaststroke). Green turtle nests are characterized by a very large pit (hole) and mound of sand.
Hatchling ID: Hatchlings tend to be grey in colour with the same 4,5,4 scute pattern. They are distinctively identified by their white underbellies and trailing fin edges.  They tend to be about 5cm (2 inches) in length and weigh around 25g (0.05lb).
Favourite saying: “You so turtely rock dude!”


Next to take the stage is the loggerhead (Caretta caretta):
Average length: Can grow up to 1m (3ft)
Weight: Can grow up to 113kg (250lb)
Description: Loggerheads, so called for their distinctive large beaked head and thick neck, are found in temperate and tropical regions inhabiting both oceanic and near shore habitats. They have a slight heart-shaped carapace with a scute pattern of 5,5,5, which tends to be a reddish brown in colour while their neck and flippers tend to be reddish brown on top, but pale yellow underneath.
Diet: The loggerhead is predominantly carnivorous with a very powerful set of jaws used to feed on
crustaceans, whelks, and commonly conch.
Track pattern: When females come up onto the beach to nest their tracks are asymmetrical in pattern. This is because they move their front flippers alternatively, like swimming the front crawl. Loggerhead nests are small and scrappy compared to green turtle nests.
Hatchling ID: Hatchlings tend to be in dark brown to grey in colour with dark or sometimes pale yellow underbellies (in contrast to the white underbellies of green turtle hatchlings. Again they have the same 5,5,5 scute pattern as adults and they are generally around 4cm (1.5 inches) long and weigh about 20g (0.04lb).
Favourite quote: “Does this conch make my neck look big?”


And last but by no means least – the hawksbill (Eretmochelys imbricata):
Average length: Grows up to 65-90cm (25-35inches)
Weight: Can grow up to 45-70kg (100-150lb)
Description: The hawksbill is smallest turtle found nesting and residing in the Cayman Islands. They have a long elongated head that tapers down to a sharp beak point, and are found in seas associated with a healthy coral reef system. They have a distinctive shell pattern, where the carapace is dark golden brown, with streaks of orange, red and or black with overlapping scutes in a 4,5,4 pattern and serrated edge at the back of the shell.
Diet: Being associated with a healthy coral reef, hawksbills feed on coral, algae, invertebrates and their favourite, sponges.
Track pattern: When females come up onto the beach to nest they have an asymmetrical crawl pattern. It is very hard to identify the difference between loggerhead and hawksbill tracks. However, from personal observation, the hawksbill track tends to have a very distinctive tail wiggle through the entire up and downward track, and the hawksbill tends to nest in areas of vegetation. Definite species identification can be made through night-time tagging surveys or by examining hatchlings or embryos after nests hatch.
Hatchling ID: Hatchlings tend to be in dark brown to reddish brown in colour with dark brown underbellies. Again they have the same 4,5,4 scute pattern and are generally around 4-5cm (4-5 inches) long and weigh 15g (0.03lb).
Favourite quotes: “Really, another picture...fine... all I wanted was to have my lunch in peace and quiet!”



And that’s that folks! Remember these key identification points: 1) the number of scutes, 2) the head and beak shape, 3) are they eating and if so what? And finally 4) track patterns (if you are lucky enough to stumble across a turtle or turtle track on the beach).      

So why not impress your friends with your new found knowledge!

Until the next blog!


Luc :) 

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