‘It’s the circle of life!’

Nants ingonyama bagithi Baba, Sithi uhm ingonyama… (Lion King – opening scene ;)) Ok so there may be no Pride Rock or Elton John involved, but the sea turtle life cycle is very long with many different hurdles from the moment a turtle lays her eggs until her offspring can reproduce. 

So let’s start at the very beginning (a very good place to start!): the female turtle will crawl onto the beach after dark and will start the nesting process. Once she has located her desired nesting site she will start to dig her nest. Using her powerful front flippers she will start to carve out a big pit, the body pit. Once satisfied she will then use her back flippers and carve out a cylindrical egg chamber as deep as her back flippers can reach (up to a massive 1 meter – 3 ft – depth). When she can dig no further she will lay between 100-150 eggs in the chamber. On completing her laying, she will then cover the eggs with her back flippers and then will use her front flippers to cover her pit and camouflage the nest. She then returns to the sea and will continue to nest a further 3-6 times within the season, but she will never see her offspring again.                                        The eggs will remain incubating in the sand for 50-70 days before the hatchlings will emerge. Unlike you and me turtles do not have an X and Y chromosome and the sex of the hatchlings is determined by the temperature in the middle 3rd of the incubation phase. Temperatures of 28°C (82°F) or below produces all male offspring, 32°C (90°F) or above produces all female and 30°C (86°F) produces a mixed sexed clutch.                  Once they have hatched baby turtles will orientate themselves towards the ocean using the reflection of the stars and moon off the sea's surface (there are issues with development on the beaches misorientating hatchlings away from the water, but we will tackle this subject in an upcoming blog J). They will swim out as far as they can, known as the 2 hour hatchling frenzy, until they are picked up by the ocean currents. While they are in this frenzy they will not eat anything as they have their yolk sac - a packed lunch, which they have absorbed during development, sustaining them until they are out of immediate danger. They will then drift with the currents out into the open ocean where they will remain for a period of time which has not yet been identified and thus the phase is know as the 'lost years', where they hide within floating debris or Sargassum grass using it as a shelter from predators and feeding off the fish larvae, algae and plankton that are found under these habitats.                 After several years floating in their shelter, juveniles will migrate back to coastal waters when they are about the size of a dinner plate, where they adopt several specific feeding (foraging) sites. As we learnt last week, green turtles are true herbivores and will feed in the shallow lagoons, whereas the loggerheads and hawksbills will feed off-shore on coral reefs. Juveniles will not return to their natal site but reside in the areas where the currents distributed them, meaning that juveniles from distant natal areas live together until they reach adulthood.                                                                          Upon reaching adulthood, 20-25 years later, males and females will migrate thousands of miles from their foraging grounds to their natal breeding grounds. Because of the vast distances covered in travelling, adults will typically only make this voyage every 2-3 years. When they reach the breeding grounds, courtship takes place approximately one month before the before the nesting season, and can be with multiple males. Once courtship has taken place the female stored enough sperm to fertilize her clutches for the season, and when it is time she will make her way to the very same beach on which she originally hatched and will lay her nest, thus the cycle is complete.                                              And that’s the cycle in a nut shell. A staggering 20-25 years before a single female can start to reproduce. That’s a long time to try and survive for and we will touch on the threats to sea turtles in the next blog, and what’s even more astounding is we still do not know how long they can live. One of life’s little mysteries!

There’s just enough time for a quick anecdote (Anniedote – she’ll be proud of me!) if I may which highlights the massive span of time these individuals have before they can reproduce. My mum grew up for a period of time in Northern Cyprus and the turtles that she saw hatching on the beach are quite possibly some of the same turtles that I have been monitoring in my years of volunteering in Cyprus… Now that is also the circle of life! J

Until the next time folks!

Luc J

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 :)