Africa: Eye to Eye with the Unknown

Title: Africa: Eye to Eye with the Unknown
Author(s): Michael Bright
Release year: 2013
Publisher: Quercus

Why in Database: Book related to the nature series with the same title. There are a lot of turtle fragments in it, one very long and a few small ones. Plus some graphics that we also show.

The first three pieces are minor references:

An isolated population of Nile softshell turtle shares Turkana’s waters with the crocodiles.

The presence of the turtles however, indicates that at some stage in the past, when rainfall in the area was far greater that it is today, Turkana was connected to the Nile river system.

The turtles hang out on the shores of a large island, known as Central Island, also a favoured nesting site for crocodiles.

The next piece is the longest:

EPIC RACE FOR LIFE

First a dusty head and then a pair of disproportionately large flippers push up through the sand: a turtle hatchling, no more than 7 cm (3 inches) across and a dirty grey colour, appears on the surface of the dune. Its limbs flail about wildly as it stretches and strains every tiny muscle in trying to free itself from the clinging sand. It had been incubating for two months underground, before breaking out of its leathery egg case and digging its way upwards, the danger of being buried alive never far away. It and its nest mates over a hundred of them – waited patiently just below the surface for the right moment to make the final push.

A sudden drop in temperature at sunset was the trigger. Now, in the twilight, the baby turtle finally emerges, but the pit from which it has tried to escape collapses, It’s near disaster. The turtle tumbles back down, but it’s still on top of the heap, so it scrambles over the tangle of heads and flippers of the other hatchlings and heaves itself onto the surface of the sand. The brightness of the sea in front and the darkness of the land behind the nest ensure that this tiny scrap of life heads in the right direction, but there are many obstacles blocking its route, and the youngster has the dubious distinction of being a handy bite-sized packet of protein, so there are many here taking a close interest in its first journey to the sea… in fact, its first journey anywhere.

Flotsam, washed up and dumped on the shore, becomes an insurmountable barrier, and even ripples in the sand slow down the hatchling’s dash across the beach. It must not stop, but keep on going. It has to reach the water’s edge in the shortest possible time. Its life depends on it. Its limbs are actually adapted for swimming but it’s exceptionally nimble over the sand. On dry, loose sand it moves forward by pushing against the solid wedge of sand particles that forms behind its flippers, and when it reaches the wet sand it advances by digging in with a claw on each flipper so it doesn’t slip.

All around it, other baby turtles are making the same headlong rush to the sea. They come from the many hundreds of nests dotted along the beach, but not all will make it. Pied crows swoop down and pick off any hatchlings tangled in tide-line debris, and ghost crabs intercept many of those that do get through, hauling them into their burrows in the sand before tearing them literally limb from limb. It will be a miracle if even a handful reach the ocean, for the first wave of hatchlings bears the brunt of attacks; but the sacrifice of a few hundred ensures that the following thousands have a better chance of making it to the sea.

The hatchling is a baby green sea turtle, born on the island of Mwali (Moheli) in the Comoros Archipelago. She’s a female, as are all her nest mates, their sex determined by the temperature of their nest. While the eggs were incubating, the temperature of the sand regularly rose above 29°C (84.2°F), so the entire clutch are females, Below 26°C (78.5 F) and they would have been males. It means that this little female hatchling will be out at sea until her twentieth birthday, when shell return to this same beach to deposit her first batch of eggs in the sand… that is, if she ever reaches the water’s edge. Only 30% make it this far, and the beach is only the first hazard. In the shallows there are more predators waiting and more obstacles to negotiate The hatchling swims powerfully, her head down and flippers pulling hard against the water. As she comes up for air she switches to doggy-paddling, raises her head above the surface for a quick breath, and then powers on through the surf, except that at 25 g (less than an ounce) the baby is turned over in the breaking waves and battered against the sand.
On reaching clear water beyond the surf line she surfaces for air again. It’s what the kites have been waiting for. They swoop down and scoop hatchlings from the surface, and even those hidden below are not safe. There are sharks offshore ready to intercept them on their way to deeper water. Even fewer will have made it this far, but the little female ploughs on towards the open sea, though her pace is gradually slowing, until it levels off after about twelve hours. All the while, she’s been swimming almost non-stop using the remnants of her yolk sac for energy; and she carries over ten times more yolk than she needs in her break for freedom so that she can keep going without feeding for up to fourteen days.
By that time, she’ll be swept along in the Mozambique Channel in a series of enormous anti-cyclonic eddies, each up to 300 km (186 miles) across. Where she and all the other survivors go for the next twenty years is a mystery (and only one in a thousand survives to adulthood), but wherever that might be will depend on the strength and direction of the ocean currents, especially those in the Mozambique Channel, birthplace as well of the formidable Agulhas Current.
The equatorial sun to the north powers the system, and it swirls inexorably southwards between Madagascar and the African mainland. Here, it strongly influences the climate of much of Mozambique, one factor that helps maintain an extraordinary and unexpected diversity of fauna and flora unsuRepublic of South Africassed in much of the rest of Africa.

The next three are captions to the photos appearing besides the above long fragment:

Breaking out of its leathery egg case and digging its way upwards, for a baby turtle the danger of being buried alive is never far away. All around it, other babies are making the same headlong rush to the sea… but not all will make it.

When they emerge from the sand, green sea turtle hatchlings head unerringly towards the sea, but all manner of dangers are waiting for them on the beach. Most make their run at night, when fewer predators are about, but the latecomers must run the gauntlet in daylight and as a consequence the casualty figures rise.

On reaching the water, the hatchling heads for the open sea, searching for upwellings where food is concentrated. It will live in the ocean for up to five years, feeding on zooplankton and small marine creatures, before heading for sea grass meadows along the shore where, while still an immature juvenile, it becomes a herbivore.

The next three fragments are again, smaller ones:

The water and all of floating life immersed in it (including, no doubt, a certain sea turtle hatchling growing a little every minute) is propelled southwestwards at about 6 knots (6.9 mph) to the Wild Coast of South Africa.

The dwarf ground sloths of the Caribbean island arc were next, about 6,000 years ago, followed by the giant crocodiles and giant land turtles of New Caledonia and nearby islands 3,000 years ago, the gorilla-size lemurs of Madagascar 2,000 years ago and New Zealand’s giant birds – moas and the giant Haast’s eagle – by AD 1400.

Together with assistant producer Rosie Thomas and production coordinator Hannah Smith, Hugh had to ensure the dead whale (a Bryde’s whale as it happened) was made safe and then mobilise a film crew; the only problem was that Hugh was filming turtle hatchlings in the Comoros Islands.

The following excerpt is about Mozambique’s Bazaruto Archipelago: