A Little Cheloniology to Contemplate

After a lecture on cosmology and the structure of the solar system, William James, the American philosopher was accosted by a little old lady.
“Your theory that the sun is the centre of the solar system, and the earth is a ball which rotates around it has a very convincing ring to it, Mr. James, but it’s wrong. I’ve got a better theory,” said the little old lady.
“And what is that, madam?” inquired James politely.
“That we live on a crust of earth which is on the back of a giant turtle.”
Not wishing to demolish this absurd little theory by bringing to bear the masses of scientific evidence he had at his command,

 James decided to gently dissuade his opponent by making her see some of the inadequacies of her position.
“If your theory is correct, madam,” he asked, “what does this turtle stand on?”
“You’re a very clever man, Mr. James, and that’s a very good question,” replied the little old lady, “but I have an answer to it. And it’s this: The first turtle stands on the back of a second, far larger, turtle, who stands directly under him.”
“But what does this second turtle stand on?” persisted James patiently.
To this, the little old lady crowed triumphantly,
“It’s no use, Mr. James—it’s turtles all the way down.”

J. R. Ross, Constraints on Variables in Syntax, 1967

The turtle shell is a highly complicated shield for the ventral and dorsal parts of turtles,completely enclosing all the vital organs of the turtle and in some cases even the head.

Or perhaps you’d prefer some testudinology? It’s all the same to us: they both mean the study of those amazing aquatic creatures, turtles. In scientific terms, turtles are diapsids of the order testudines, and they are creatures characterised by their bony (or cartilaginous) shell that acts as a shield. Oddly, those shells developed over millions of years from their original ribs. Thinking about it, this particular Darwinian evolvement makes a great deal of sense: not only do the ribs hold everything together, they also act as a suit of armour. It would certainly have been an improvement on the current human evolutionary state, particularly for those amongst us who ride (and fall off) bicycles. But probably not an aesthetic enhancement.

As the evolution of the carapace indicates, turtles are ancient. They date back to the mid-Jurassic period – the calendars at the time would have read 170 000 000 BCE – predating those other surviving dinosaurs and reptiles, the crocodiles and snakes. Sticking to the scientific nomenclature for a moment, turtles are ectotherms, more commonly known as cold-blooded, and are amniotes too, meaning they lay their eggs on land. Not to be confused with anamniotes, who lay their eggs in water. But that’s enough of the scientific terminology: anyone who has seen a turtle in the water will know that they are fascinating creatures. I had an almost surreal experience when snorkelling off Key West; I was suddenly overtaken by a dozen or so green sea turtles, all paddling along serenely in formation. For a few brief minutes I was an honorary turtle, until I remembered I had to breathe and spluttered to the surface. Turtles also have to surface to take in oxygen, but they are a lot more efficient at taking on air in an ‘explosive’ inhalation, and a rapid exchange of oxygen lets blood deliver the gas to body tissues even under the pressures of deep diving. They are amazing creatures, and worthy of our respect – and conservation. Just this week we read of a local turtle that had to be freed from a discarded fishing net – a common death for migrating turtles. Just one more way that man has discovered to kill off species; not only do we plunder the ocean for her treasures, but our castoff nets trap and kill countless innocent creatures.

Only certain sharks and humans are turtle predators: specifically the tiger shark. (The thought of how sharks munch through the turtles armour is disconcerting; if they can crush that carapace, what chance do soft humans have? A little pay-back, perhaps…) A bigger problem for turtles is the reproductive cycle, and the impact that humans are having on that process. Turtles migrate great distances to reach their favourite beaches: up to 2 600 kilometres across the oceans. The habitat of the turtles are tropical and sub-tropical oceans, and these particular areas are also very popular with us humans, who love lying around under the summer sun and flopping around in temperate water. Which means that many of the turtles favourite egg-laying beaches have become ideal real estate for the archetypical ‘holiday paradises’ that attract recreational humans.

Baby Turtle heading to Ocean
Baby turtle heading to the Ocean after hatching from its ancestral natal homing beach.

Turtles return to the beach where they hatched to spawn (known as natal homing), and it must be extremely annoying after a six month swim to find your beach covered with oiled humans, umbrellas and plastic waste. The Indian Ocean, South East Asia, Central America and the Western Pacific are all favoured by both turtles and holidaying humans, and there is no difficulty in working out who comes off second best. An aside on the egg-laying process: eggs that hatch on a beach with a mean temperature above 30˚C are female; those under 30˚C are predominantly male. We say predominantly, because the eggs in the centre of a clutch of eggs also incubate over 30˚C temperatures. There is probably a lesson for humans in there somewhere, but we aren’t going to speculate.

In recent decades turtles have moved from unprotected exploitation to global protection, but the threats remain unabated. Most dangerous are unintentional threats, including boat strikes, fishermen's nets that lack turtle-excluder devicespollution and habitat destruction as mentioned above. Turtle populations range globally from threatened to critically endangered: in addition to management by global entities such as the IUCN and CITES, specific countries around the world have undertaken conservation efforts. Whether this will reverse the exploitation remains to be seen, but there have been successes in some areas, most notably Hawaii.

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Waterfront Charters urge everyone to become conservation orientated: whilst turtles may seem a distant species to most of us, they are part and parcel of our underwater world. Each extinct species is a huge loss to our eco-system and our planet, and we all need to become aware – whether it is through active involvement or simple eco-awareness, we have a responsibility. Waterfront Charters have a partnership with CapeRADD, a group of marine scientists who work tirelessly to educate on the marine environment, conservation and research. We highly recommend you consider having one of these professionals aboard when you charter one of our vessels: their underwater videos and expert knowledge are fascinating, and we know that the message they are spreading is vital. All details on the website. Who knows, you may discover that it’s turtles all the way down after all…

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