21st January 2020
Welcome to our new and Fun Fact Filled Turtle Tuesdays. As Mem is a marine biologist and a Sea Turtle expert we’d like to share some interesting facts with you about these amazing and wondrous creatures over the following weeks.This will be an ideal opportunity to ask an expert those questions about Sea Turtles you may have had but never got an answer too. Over the weeks we’ll look at their life cycle and some little known but very interesting facts about these fabulous animals.
We thought we would start with some interesting facts about Sea Turtles. They have evolved from their land dwelling cousins the tortoises making them reptiles, in both cases their rib cages have developed to provide a hard exoskeleton to protect them. Sea Turtles shells have become flattened compared to tortoises, allowing them to be more streamlined and move through the water with less resistance. Their front legs have become elongated and flatted and are used to propel them through the water at high speeds, their back legs also have flattened but have not increased much in length, Sea Turtles use their back legs more like rudders to change direction while swimming. This flattening of the shell has meant that they have lost their ability to retract their head and legs into their shell like tortoises. Other than when they lay their eggs Sea Turtles spend their entire lives at Sea, they can be found in almost every ocean basin in the world, they migrate long distances to feed, often crossing entire oceans between feeding and breeding grounds.
As divers we often encounter Turtles in their feeding grounds, we would love to see some of your Turtle photos and hear where they were taken.
I’ll Start, this was a Hawksbill Turtle feeding on a reef in Raja Ampat in Indonesia
30th January 2020
Hello and welcome to another Turtle Fun Fact day this week its Turtle Thursday. With Last weeks post we learned how Turtles are reptiles and how their bodies have adapted from their land dwelling ancestors. This week I’d like to tell you more about their life cycle and really how little is actually known about their early years. As we know Sea Turtles spend their lives at sea and it is only the females that return to the beaches to lay their eggs, many believe that the female will return to the exact beach where she hatched many years previously. This is one of the most highly debated topics in Sea Turtle research, recently with the use of genetic markers scientist have been able to prove that one female logger head actually laid 4 different nests on 4 different beaches off of the Florida Keys…..so which one did she hatch on??? Regardless of the answer the life cycle of Sea Turtles is known for the most part. We know that Sea Turtles actually have different feeding and mating grounds, they will spend most of the year in their preferred feeding ground, adults will migrate to breeding grounds which are located adjacent to nesting beaches, Males will do this annually where as females will only migrate there every 2 or 3 yrs once they are ready to breed. It is such a demanding and strenuous time on the female’s body that they do not lay eggs every year. Depending on the species of Turtle they will become adults and ready to breed between 20-40 years of age, both males and females will congregate in front of the nesting beaches; the males will compete to be the one to mate with a female. The males have special nails/claws on their front fins which are curved to hold on to the females shell while mating, here the female will then swim the 2 of them up to the surface to breath, she will do this for the next 6-7hrs (yes that is correct in hours and not Minutes) that it takes for mating to be completed. After mating it takes 2 weeks before the eggs are ready to be laid and in this time she may well have mated with several males and in fact her clutch may have a number of different Daddies. She may lay 2-4 nests per breeding season with each clutch of eggs varying between 70-120 eggs per nest, the larger the female the larger the clutch of eggs will be.
4th February 2020
Hello and welcome to another Turtle info day, in last weeks post we looked further into Sea Turtles breeding behaviours this week we’re looking at nesting. After mating the females will spend a lot of time resting on the bottom of the sea bed just in front of the nesting beach where after 2 weeks she’ll pull herself out of the water and search for a good spot to lay her eggs, not all nesting exits are successful, if the female isn’t happy with the location or is disturbed before starting to lay her eggs she will return to the water with her clutch still inside her and try again, if she continues to be unsuccessful she will ditch the eggs in the sea. Female turtle have a very special ability to control their stress hormones during breeding, in fact they are able to completely halt responses to stress over the breeding season, they actually stop/reduce the production of hormones released by the hypothalamus in response to stress, unlike the males who at this time of year are very stressed and producing lots of stress hormones. Once a female has decided on the perfect spot for the nest she begins to dig the hole of the nest with her rear fins using them to scoop out the sand. This is done with extreme care as she carefully places each scoop of sand to the side of the nest, once the egg chamber is between 70-100cm deep she begins to lay. Once she’s started laying there is nothing that will deter her from her task at hand, researchers actually use this time to take measurements and recordings of the female that are otherwise very tricky to record on a moving Turtle. The whole process of digging the nest and laying the eggs can take 2-3hrs. Once she has finished laying the eggs she carefully covers over the nest insuring that the last sand dug out the nest is the first sand back into cover the eggs over, this way she is keeping the same temperature and moisture level of sand over the eggs. Once covered she firmly pats down the sand over the eggs chamber and once finished she throws sand around all over to disguise the actual location of the chamber. She’ll then return to the sea where she will rest and start producing the next batch of eggs.
11th February 2020
It’s Turtle Tuesday time folks. Last week we ended with the female Turtle having laid her clutch of eggs and returned to the sea to rest as the next batch develops inside her. . Once the female has laid her eggs that’s her job done and she will never return to check on the nest or meet her hatchlings. It takes between 45-60 days for the eggs to develop and hatch, this time will vary according to the temperature of the sand the eggs have been laid in, the warmer the faster the development. Most females will lay their eggs at least 5m above the high tide line on the beach, with some laying their eggs 50-60m above the high tide line. Like other marine reptiles the sex of each egg is determined by the external temperature that the eggs are developing within, cooler temperatures produce more males and higher temperature more females, the location of the nest in relation to the high tide line has an effect as does our planets ever increasing temperatures. In Turkey we have found that the Loggerhead nests laid on Dalyan Beach are now developing at a 20:80 ratio, 20% male and 80% female where as 20 years ago we were seeing 50:50 sex ratios throughout the nests. Having more females may sound good, more females to lay more nests in the future can’t be a bad thing right? However when you factor in the survival rate of hatchlings developing into adults and continuing the cycle there is a range of estimates from 1 in a 1000 to 1 in 10,000, no matter which, the odds are really stacked against these little cuties and with less males the chances of them surviving to become an adult are extremely low. Turtles combat this with laying as many eggs as they do, as previously mentioned the number of eggs a female will lay in the nest depends on her size but each nest can have 70-120 eggs large clutch sizes help increase the odds of one little hatchling making it to become an adult. Once the nest is ready to hatch the hatchlings use a little sharp notch they have on their beaks to break free of the egg shell. Another amazing fact about Turtles is that when the egg is laid the yolk and embryo will develop in such an orientation that the little hatchling will develop head up so that when it breaks free of the egg it’s head is already orientated to the surface. Once free of the egg shell they work their way to the surface and will spend 3-4 days about 15-20cm below the surface where the weight of the sand will help straighten up their little curved bodies and remove any gunk remaining from the egg, this ‘cleaning’ helps to protect against predators. Once there is a good number of hatchlings ready (20-40) they all co-ordinate and exit the nest at the same time and make their mad dash to the sea where they will frantically swim out to open water avoiding the gauntlet of predators along the way, as the hatchlings are only about the size of a match box there are many creatures both on land and in the sea waiting to pick them off. It can take a few days for the nest to fully hatch. For those that make it out to open sea they enter what is known as the ‘Lost Years’ as its so difficult to tag theses babies and follow where they go we don’t actually know where they spend the next 10yrs or so, evidence points to them hanging out in sea kelp and floating clumps of seaweed until they have developed enough to return inshore and head for feeding grounds.
18th February 2020
Welcome to our next instalment of Turtle Tuesdays, so far we’ve looked at Sea Turtles breeding process and the development of the eggs in the nest. As we’ve discussed the odds of a hatchling Sea Turtle making it adulthood and continuing the cycle are extremely low, we mentioned the gauntlet that the hatchlings have to undergo just to make it out to the open ocean, from the second they emerge from the sand they are at risk of being swallowed up by Foxes, Badgers, Birds, land crabs and even domestic animals such as cats and dogs. Once the hatchlings have left the nest they use the light levels to guide them to the water, often hatching coincides with a full moon which shines brightly over the sea, making the seaward direction lighter than land, unfortunately if there are lights on or behind the beach the poor hatchlings head the wrong way and unless rescued by a passer by they’ll never make it to the ocean before dehydrating, being squashed or gobbled up. Scientists have been able to show their attraction to light by effectively covering the nest with a hut who’s door opens towards to the land, they noted all the hatchlings head out the door and turn 180 degrees and head right for the sea.
Once in the water the threats are still very real, at this small size (about the size of a match box) the hatchlings can only hold their breaths for a few minutes before they need to return to the surface for air making them easy pickings for sea gulls and other marine bird species, large fish, crabs, octopus, morays, well pretty much anything that can grab them takes advantage of these tasty and nutritious little morsels.
For the hatchlings first few weeks they do nothing but focus on getting out to the open ocean, they don’t need to forage for food as they have a reserve of nutrients they absorbed internally from the yolk before they hatch, they can survive on this yolk reserve for up to 2 weeks. Due to their tiny size it has only been recently scientist have been able to attach tiny transponders to the hatchlings and they have finally been able to record that once out of the nest the hatchlings do in fact head to open sea. There they will find shelter in floating kelp masses or Sargassum seaweed clumps where they will feed on plankton and other tiny creatures hanging out in the shelter of the weeds, this time is known as their lost years as we know very little about their time in the open oceans. Over the years they will spending their time feeding and growing, in their first year they’ll grow up to 5cm in length, this is their fastest growth phase, as after 5ys or so they will so down to roughly 1 cm a year. They keep growing their entire lives and we use their shell length as an indicator of their age.
25th February 2020
Welcome to another installment of our Turtle Tuesday info day. Last week we covered the hatchlings leaving the nest and heading out to open sea where they spend the next 10-15yrs growing before they head back closer to the shore and to feeding grounds where they will continue to grow until they are large enough to breed, this time scale varies with different species and it can be between 20 – 40 years before the juveniles have grown and developed enough to begin the cycle and continue it again and again.
All the details and information I’ve given so far has been general for all the different species of Sea Turtle. There are 7 confirmed species of Sea Turtle and one that is still under review as to if it is in fact an 8th species or a sub species. Depending on what you read or what research your looking at you’ll find that some say there are 7 and others will say there are 8 species of Sea Turtle. I personally lean more towards the research that shows there is an 8th species; The Pacific Black Turtle (Chelonia mydas ssp. agassizi). Black sea turtles are unique members of the sea turtle world. While currently classified as the same species as the green sea turtle, the pacific black sea turtle has several features that make it one of a kind! I’ll be looking into each species in more detail over the following weeks.
Illustrated in the 3rd image you can see that each species has different characteristics that we can use to distinguish between each species. To be able to ID effectively you do need some basic Turtle anatomy knowledge, which I’ve covered in the 2nd Image this week. Using these key features we can then identify which species of Sea Turtle we are looking at. This weeks Third Image covers all 8 species and has a great key for all 8 species and you can download the PDF here for future reference. http://www.seaturtle.org/documents/ID_sheet.pdf
10th March 2020
Hello and welcome to another addition of our weekly Sea Turtle installments, 2 weeks ago I introduced you to the 7/8 different Sea Turtle Species, this week I’d like to start looking in more detail into each and every species starting with the largest of all, the Leatherback (Dermochelys coriacea).
Leatherbacks belong to a different taxonomic family than all the other sea turtle species found in the world making they extremely unique. They have existed in their current form since the age of the dinosaurs.
The Leatherback receives its name from its unique shell, which unlike any of the other Sea Turtle species is not hard, in fact their top shell (carapace) is about 1.5 inches thick and consists of leathery, oil-saturated connective tissue overlaying loosely interlocking dermal bones. Their carapace has seven ridges that run along its length and they taper to a blunt point, this helps the Leatherback move more effectively in water. Their front flippers lack claws and scales (again unlike any other Sea Turtle) and are proportionally longer than in other species. Both their ridged carapace and their extra large fins make the Leatherback uniquely equipped for long distance foraging migrations.
Leatherbacks are highly migratory, with some individuals swimming over 10,000 miles a year between nesting and foraging grounds. They are strong swimmers and can dive to depths of approximately 1,200m (nearly 4,000 feet), deeper than any other turtle and most marine mammals; they can stay underwater for up to 85 minutes before needing to surface for air. Leatherbacks have a unique system of blood supply to their bones and cartilage. This enables their body temperature to stay several degrees above the ambient water temperature allowing them to tolerate cold water, much like a mammal.
Once prevalent in every ocean except the Arctic and Antarctic, the Leatherback’s population is rapidly declining in many parts of the world. The populations are divided between the Pacific and Atlantic populations. The Pacific population of Leatherback sea turtles has suffered most over the last twenty years: as few as 2,300 adult females now remain, making the Pacific Leatherback the world’s most endangered marine turtle population. All Leatherback turtle populations are listed as endangered. They face threats on both nesting beaches and at sea. The greatest of these threats worldwide are incidental capture in fishing gear and harvesting of Leatherback eggs and adults for their meat.
Sea turtles have been intentionally killed for their meat and skin for hundreds of years. The primary threat to Leatherback turtle populations worldwide is bycatch in fishing gear. Bycatch primarily occurs in gillnets, longlines, trawls, and trap/pot fisheries. Sea turtles may die after ingesting fishing line, balloons, or plastic bags, plastic pieces, and other plastic debris, which they can mistake for their preferred food, Jellyfish.
Populations numbers are difficult to record due to the adult female Leatherbacks frequently nest on different beaches, making nesting population estimates and trends very difficult to monitor. However, it is estimated that the global population has declined by at least 40% over the past three generations. It is believed there are between 34,000 – 36,000 nesting females worldwide. Females nest at intervals of 2 to 3 years, though recent research has indicated they can nest every year. When they do breed each female can lay between 4 to 7 nests per season, with an average of 10 days between each nest. Female’s lay an average of 80-100 fertilized eggs per nest, the eggs are the size of billiard balls, along with the 80+ fertilized eggs there are usually 20-30 smaller, unfertilised, oddly shaped eggs, in each nest, the reason for this is believed that they are ‘Spacers’ allowing better gas exchange within the nest. Eggs incubate for about 65 days before the hatchlings emerge.
Leatherbacks lack the crushing chewing plates characteristic of other sea turtles that feed on hard-bodied prey. Instead, they have pointed tooth-like cusps and sharp-edged jaws that are perfectly adapted for a diet of soft-bodied Open Ocean prey, such as jellyfish and salps. Their jaws would be damaged by anything other than a diet of soft-bodied animals, so they feed almost exclusively on jellyfish. It is remarkable that this large, active animal can survive on a diet of jellyfish, which are composed mostly of water and appear to be a poor source of nutrients.
Despite the low nutrient content Leatherbacks can grow up to 150 – 200 cm in length, with the largest Leatherback ever recorded at 305 cm (10ft) from the tip of its beak to the tip of its tail and weighed in at 916 kg. On average Leatherbacks weighs 300 – 500 kg. Very little is actually known about their lifespan but its believed they are one of the quickest to mature at 15yrs young and are estimate to live for 30-45 years.
Believe it or not there have been recorded distributions of Leatherbacks off the coast of Britain and Ireland. Present mostly in August and September off the south and west coasts. They have also been recorded off Shetland, the Firth of Forth and in the Humberside. So keep your eyes peeled.
17th March 2020
Hello Folks and welcome to another instalment of our Turtle Tuesdays, last week we found out more about the great ocean traveller, the Leatherback. Keeping with running in size order the second largest of the Sea Turtle species is probably the most famous of all the Sea Turtles, the Green Turtle (Chelonia mydas). Adults are 3 to 4 feet in carapace length (83 – 114 cm). The green turtle is the largest of the Cheloniidae family with the largest green turtle ever found at 5 feet (152 cm) in length and 871 pounds (395 kg). Adults usually weigh between 240 and 420 pounds (110 – 190 kg).
A common misconception is that the Green Turtle receives their name from their diet, which is mainly sea grass and algae; they are the only Sea Turtle species that are for the majority of their lives are vegetarian. They in fact receive the name ‘Green’ as they have green body fat.
Many years ago when sea travel took weeks to months to cross the Oceans, Sailors would catch and store a number of sea Turtles in the ships hold for their meat, you see the turtles could be caught and then stored for months due to the Turtles ability to slow their metabolism, they are able to stay alive for months without any food, this was the beginning of their downfall as this form of meat was in plentiful supply and was the best way for the sailors to keep fresh meat in their diets during long periods at sea.
As with all other species of Sea Turtle the Green Turtle are endangered, however there is some great news for the Greens; in 2016 they went from Critically endangered to Endangered, this is the only Turtle species to show a significant increase in the population numbers, yes they are still endangered and under threat but the population is beginning to make a come back.
Green Sea Turtles have to be one of the most photographed of all the Species, this is due to the fact that their preferred habitat is where divers frequently dive; along the coastlines of temperate sea’s around islands and in bays and protected shores and especially in areas with sea grass beds. Rarely are they observed in the open ocean.
Like other sea turtles, they migrate long distances between feeding grounds and the beaches from where they hatched.
Green Turtles play a vital role in the maintenance of a healthy Sea Grass bed, they act like lawnmowers trimming the grass and keeping it in check. If sea grass beds were left unattended they grow rapidly and become so thick and dense that all water circulation around the bed would actually stop creating a toxic environment. We know sea Grass beds are vital for many juvenile fish, sea horses and other crustaceans.
Green Sea Turtles are easily distinguished from other sea turtles as they have a single pair of prefrontal scales (these are the scales in front of their eyes), rather than two pairs as found on other sea turtles. Their head is small and blunt with a serrated jaw designed for cutting sea grass and algae. The Carapace is bony without ridges and has large, non-overlapping, scutes (scales) present with only 4 or 5 lateral scutes. Their body is nearly oval in shape and their front fins have 1 visible claw. The carapace colour varies from pale to very dark green and plain to very brilliant yellow, brown and green tones with radiating stripes. This too was another downfall for the Greens as this colour and patterning was highly sought after and their shells were used to make a number of different items including jewellery, brushes and souvenirs. The plastron varies from white, dirty white or yellowish in the Atlantic populations to dark grey-bluish-green in the Pacific populations. Green Turtle hatchlings are one of the easiest to identify, as they are dark-brown or nearly black on top with a white underneath and white flipper margins. Greens have been found to be one of the longest lived of all the Sea Turtle Species with estimates of some individuals living for over 120years, generally its believed green Turtles live between 80-100 years.
The greatest threat green Turtles face in this day and age is from the commercial harvest for eggs and food. Other green turtle parts are used for leather and small turtles are sometimes stuffed for ornamental purposes. Incidental catch in commercial shrimp trawling is an increasing source of mortality. It is estimated the current Green Sea Turtle population is between 85,000 and 90,000 nesting females.
It was lovely in our first post to see all your turtle in counters and we’d love to hear and see about any more green turtle experiences you may have had.
24th March 2020
Welcome to another instalment of Aquatron’s Turtle Tuesdays. With everything going on right now we’d like to continue to provide a little distraction in these troubling times.
Last week we looked at the famous green turtle the only turtle species with some success in increasing population numbers, we’ll return to this success story and others like it involving current conservation actions in the following weeks.
This week I’d like to look deeper at the most debated of the sea Turtle species, “The Black Turtle” (Chelonia mydas agassizii). They are a unique member of the sea turtle family, while currently classified as the same species as the Green Sea Turtle (Chelonia mydas), the pacific black sea turtle has several features that makes them rather unique.
Tracing back the history of the black turtle, one important event stands out; between 3 and 20 million years ago Central America rose up out of the sea, this created a land barrier between the Atlantic and the Pacific, isolating two populations of green turtles from each other.
Black turtles are generally found in the eastern t0071a1ropical Pacific, adult’s tend to inhabit bays and protected shorelines from California down the Pacific coastline to Chile. They are not commonly seen in open oceans.
They were initially known as the East Pacific green sea turtle even though there are several differences between them and green turtles, the black sea turtle is smaller and darker in colour than the green’s (hence the name), it has a teardrop shaped carapace rather than oval and their heads are even smaller than those of green sea turtles, however they both share the same serrated jaw not found in any other sea turtle species.
Even though black sea turtles tend to be smaller than greens, they can still weigh up to 300 pounds (136 kg) and reach 4 feet (120cm) in length.
The first of the unique distinction between the black sea turtles and the greens is that they are the only sea turtle known to nest in the Galapagos Islands – black turtle nests also occur in Central America and Mexico. The second unique trait black sea turtles display is that they can been found basking in the sun along some of the Hawaiian Islands beaches, this is a characteristic not found in other sea turtle species, others will bask in the sun while floating at the surface.
There are a number of similarities that lead to the belief that these were in fact green turtles; they have a similar diet of algae, sea grass and mangrove shoots, in addition they both will occasionally eat small fish, jellyfish and other invertebrates.
But is the black turtle a unique species? Studies of skull anatomy suggest the black turtles are indeed different to greens, however DNA analysis shows that there is no genetic distinction between the two and that there is a close genetic relationship between the two types of sea turtle. Based on this evidence, they are classified as the same species. However, due to their differences, some experts consider the black sea turtle to be a sub-species of the green sea turtle, while other experts consider the black sea turtle to be its own species.
Historically, colonies of black sea turtles thrived in Mexico and Central America. The fishing industry and illegal harvest of eggs and turtles for meat has decimated these populations. Today, they are still caught illegally for food and accidentally in many types of fishing nets.
Many conservationists consider a separate species designation as important to saving the black sea turtle, as it would certainly gain additional protection status – since the black sea turtle is more threatened than the green sea turtle.
31st March 2020
Hello and welcome to another instalment of our Turtle Tuesdays, after a little detour with the Black Sea turtle last week, this week we are returning to size order after the green turtle. The next species down in size and is one which holds the biggest place in my heart; the Loggerhead’s (Caretta caretta) this is the species I have had the privilege of working with the most. Loggerheads receive their name due to having the largest head to body size of all the turtle species, their extra large head has developed due to their preferred diet; crabs, hard shelled molluscs and crustaceans. Their muscles they have developed to have the power in their jaws to crush through shells to retrieve the tasty nutritious morsal hidden inside has lead to the development of larger heads.
They are probably one of the most mis identified of all the sea turtles, often mistaken for a green turtle or a hawksbill. Loggerheads range in colour from dark brown, reddish brown too light tan. Their carapace is bony without ridges and has large, non-overlapping rough textured scutes, their carapace is heart shaped and can range in colour like their skin from a reddish brown to dark brown on top and underneath their plastron is a yellowish brown. They have short front fins with 2 short and thick with claws. Often the claws can be used to identify between adult males and females (this is true for all turtle species), the males will have a hooked shaped claw to hold onto the females during mating and the females’s claw will be straight.
Loggerheads typically measure 80 to 110 cm in carapace length (2.5 to 3.5 feet). Adults weigh between 155 and 375 pounds (70 to 170 kg), they are estimated to live between 70-90 years.
As mentioned loggerheads are primarily carnivorous and feed mostly on shellfish that live on the bottom of the sea bed. They eat crabs, lobsters, clams, mussels, and other invertebrates. Their powerful jaw muscles help them easily crush the shellfish. Loggerheads are messy eaters and this has a vital role in the balance of the marine ecosystem, all the crushed shells now provide a calcium source (as well as scraps of food) for many many small creatures that wouldn’t otherwise be able to source this mineral alone.
Loggerheads tend to prefer to feed in coastal bays and estuaries, in the shallow waters along the continental shelves of the Atlantic, Pacific and Indian Oceans as well as along the Mediterranean coast where some areas are feeding grounds and others are nesting sites.
They nest every 2 to 4 years, laying 3 to 6 nests per season, with approximately 12 to 14 days between each nest. Clutches average of between 100 to 130 eggs per nest. The eggs will incubate for 40-60 days.
Loggerheads are listed as venerable with decreasing nest numbers it is feared they will soon have their status changed to endangered.
Their greatest threat is loss of nesting habitat due to coastal development, predation of nests, and human disturbances (such as coastal lighting and housing developments) that cause disorientations during the emergence of hatchlings. Other major threats include incidental capture in longline fishing, shrimp trawling and pollution. Incidental capture in fisheries is thought to have played a significant role in the recent population declines observed for the loggerhead.
It is estimated there are between 40,000 and 50,000 nesting females. It’s important to understand that population estimates on all species of sea turtle are based on the number of nests recorded, this of course won’t include males or juveniles. There are a number of different projects underway with fin tags and satellite tracking, sea turtle research and conservation is a long and slow process partly due to the number of years sea turtles take to reach maturity and reproduce.
7th April 2020
Welcome to our next instalment of Turtle Tuesdays, next in our size order is one of the least studied and most unusual of all the sea turtles, the very unique Flatback Sea Turtle (Natator depressus), often known as the Australian flatback as its native to the northern coast of Australia. It receives its name from (yes you guessed it!) its flat carapace (shell). All other sea turtle species have a curved carapace including the leatherback, however the flatback sea turtle has a more oval carapace lacking in ridges and protuberances, making it appear flat and smooth. Their carapace is grayish-green or olive green in colour with a slight down curve before a distinctive up curve around their outer margins.
Their fins and the rest of the body is a yellowish light green, with their plastrons (the underside of the shell) being pale yellow like most other turtles. These unique features make the flatback one of the easiest turtles to identify.
The flatback has the smallest geographic range of all turtle species (making their lack of research surprising). Their distribution is restricted to tropical regions of the continental shelf and coastal waters of Northern Australia, Southern Indonesia, and Southern Papua New Guinea. They do not have an oceanic phase or undertake long open ocean migrations like other sea turtles, and are usually found in waters less than 60m (200ft) deep and they seldom enter open oceans or venture far from the continental shelf.
Breeding and nesting occur on beaches of the north of Australia, southern Indonesia, and Papua New Guinea. Australia has the largest concentration of females nesting on Crab Island in the NE Gulf of Carpentaria in Queensland.
Some females will lay up to four nests per season with an interval of 13 – 18 days between nests. They breed any time of the year, however breeding increases during the months of June, July and August.
In comparison to other sea turtle species flatbacks lay fewer eggs per nest with an average of just 50 eggs. Despite this their eggs and hatchlings, are proportionally larger than other species. The eggs have a diameter of approximately 2 inches making them slightly smaller than leatherbacks and larger than green turtle eggs. The eggs will hatch around 55 days after the mother has laid them. Once the hatchlings emerge they too are larger than other turtle hatchling, it’s believed their larger size aids the hatchlings in evading predators. You’ll see from the hatchling comparison photos that flatback hatchlings are almost as large as leatherbacks hatchlings.
There are zones close to the Great Barrier Reef that makes up part of their distribution, here there are abundant food sources and an environment full of marine life. However, they tend to prefer to stay in areas with soft sea beds either sandy or covered in marine vegetation, they do not inhabit coral reef systems but mearly visit.
As their carapace is thinner than other turtles, it can be easily damaged by hard substrates, it’s believed they stay away from rocks and rocky seabeds to prevent any injury.
The diet of the flatback sea turtle is varied and omnivorous. They prey on species found in shallow waters including mollusks, jellyfish, shrimp, squid, white corals, sea cucumbers, and seagrass. Adults can weigh up to 90 kilos (200lbs) and measure upto 1m in length (3ft).
Adult Flatbacks have a few marine predators; killer whales (Orcinus orca), some species of sharks and saltwater crocodiles. Adult female fallbacks have been observed being attacked by crocs while attempting to nest. On land, they have several natural enemies that eat their eggs or attack the hatchlings such as foxes, dogs and dingos, lizards, sand monitors, birds-including night herons and pelicans, even feral pigs will consume almost their entire nests on some beaches.
Flatbacks have a conservation status of “Data Deficient” in the Red List of the International Union for the Conservation of Nature (IUCN). This classification means that there is not enough information to assess their status as there is no accurate data available on their population numbers and trend. However, estimations believe there to be around 10,000 nesting females.
Other threats to this species include loss and degradation of their habitat, illegal traffic of eggs, direct capture for meat consumption, bycatch, climate change and ocean pollution are some of the greatest threats derived from human activities.
The flatback sea turtles are perhaps one of the least threatened of all sea turtles by bycatch due to their preference to stay in shallow waters where less fishing takes place.
The Flatback is a Turtle I have yet to encounter, have any of you ever seen one?
Watch this space for weekly turtle posts from our very own Mem.