The Search for Nesting Turtles
by Nancy Knudsen on 15 Nov 2007
The wind that is preventing us heading south from Port Bundaberg is beating up the surf on the beach tonight.
Mon Repos beach at sunset BW Media
It's pitch dark, and we just have to trust that the unseen sand will be flat as we lean, staggering a little, against the wind, clutching our wind jackets around us.
We're here looking for nesting turtles - the Blackwattle crew, friends the de Torres and a group of other fare-paid would-be turtle watchers. After so many cruising years of watching turtles and even sometimes swimming with them, the promise of seeing them come up a beach to nest has been irresistable
We can hardly hear each other for the wild surf, and the Ranger who is leading us has to shout high pitched instructions. Above the night sky is brilliant with stars, small windy clouds rushing low overhead.
''Stay behind me'' she screams,''I am looking either for a turtle or her tracks – they're so wary when coming up the beach – easily disturbed, and will go back to the sea. But they're deaf to the pitch of our voices.'' (Well, I think, they wouldn't be able to hear us over the surf roar tonight anyway.)
We're at Mon Repos Beach (pronounced 'Mon Reepowe' ), and we're sneaking somewhat loudly, straining to see any blob or track against the darkened sand. We've been deprived of our torches and mobile phones, and have no idea where we're headed. We're most likely to see loggerhead turtles, we're told, as this is the busiest breeding beach for loggerheads in the South Pacific. It's early in the season though, so we've also been told not to be very hopeful.
But tonight we are lucky – the ranger sees the tracks first. It's not a loggerhead - she has recognised the tracks of a flatback turtle. ''Stop! Don't move! Wait here!'' she yells. So we wait, windblown, a little clutch of lost tourists, abandoned for a minute in the dark while she surveys the scene, finds the huge turtle, and comes back telling us just where to stand to watch her digging her hole. The turtle can't look backwards, and she can't hear, so we form a little obedient semicircle of watchers behind her, and the Ranger arranges a small LED torch to illuminate the turtles backside. I feel intrusive – I wouldn't want a bunch of tourists watching ME laying my eggs.
But of course we watch. The turtle is a enormous, and she laboriously digs with her back flippers only. It's so slow I feel like rushing in to help. After about 20 minutes, she appears to sink gratefully onto the hole and lets go of her eggs. We can see it all so clearly. They seem to come two at a time, soft slippery things, which fall deep into the hole – no they don't break, they are rubbery things, soft, mottled white and slimy.
Once she starts dropping her eggs, Rangers appear out of the dark from everywhere to identify her. They measure her, check her tags – yes she's a tagged one. They can even tell her history. |She's been coming to this beach since 1987 – a very experienced nester. She's 100 kilos in weight, 97cm long – a formidable woman indeed. While laying, she is no longer wary, and oblivious of humans. Photos are now allowed, and torches of the Rangers light the area.
Now she'll crawl back to the water. But there's more. She has reached the grass, which is the signal to start digging. However, on this occasion she hasn't moved far enough up the beach. The eggs in this spot will be subject to high tides destroying them. So the Rangers will relocate the eggs – about 50 of them - to a similar man-made hole higher up the beach. This way 50 more baby turtles will have the chance to reach the ocean, grow to adulthood, and repopulate the ocean's sadly depleted turtle populations.
As we are led back along the black dark beach like children to find to the boardwalk which leads to the Ranger Headquarters, we're delighted to be stopped by two more turtles scrambling in slow motion up the beach. ''It's raining turtles tonight!'' exclaims the pleased Ranger. We must wait each time for the loggerheads – ''They are loggerheads – I can tell by their tracks''- to reach the high parts of the beach before we creep by down at the surf line – leaping out of the way of the more aggressive of the waves – back to the lights of a more familiar evening.
Just another in the long line of marvelous experiences available to the cruising sailor...
About Sea Turtles:
On Mon Repos beach, three types of turtles come to nest – the Loggerhead, which, according to Mon Repos rangers, is ''endangered'', and the Flatback and the Green Turtle, which are listed as ''vulnerable''.
However, all sea turtles share some common features.
First, they have an extraordinary sense of time and location. They are highly sensitive to the Earth's magnetic field and use it to navigate. The longevity of sea turtles has been speculated at 80 years. The fact that most species return to nest at the locations where they were born seems to indicate an imprint of that location's magnetic features.
After about 30 years of maturing, adult female sea turtles return to the land to nest at night, usually on the same beach from which they hatched. This can take place every two to four years in maturity. They make from four to seven nests per nesting season.
All sea turtles generally employ the same methods when making a nest. A mature nesting female hauls herself onto the beach until she finds suitable sand on which to create a nest. Using its hind flippers, the female proceeds to dig a circular hole 40 to 50 centimeters deep. After the hole is dug, the female then starts filling the nest with eggs one by one until it has deposited around 150 to 200 eggs, depending on the turtle's species. The nest is then re-filled with loose sand by the female, re-sculpting and smoothening the sand over the nest until it is relatively undetectable visually. The whole process takes around thirty minutes to a little over an hour. After the nest is laid, the female then returns to the ocean.
Some of the eggs are unfertilized 'dummy eggs' and the rest contain young turtles. Incubation takes about 2 months. The length of incubation and the gender of the hatchling depends on the temperature of the sand. Darker sands maintain higher temperatures, decreasing incubation time and increasing the frequency of female hatchlings. When the eggs hatch, these hatchlings dig their way out and seek the ocean. Only a very small proportion of them (usually .001%) will be successful, as many predators wait to eat the steady stream of new hatched turtles (since many sea turtles lay eggs en masse, the eggs also hatch en masse).
The hatchlings then proceed into the open ocean, borne on oceanic currents that they often have no control over. While in the open ocean, it used to be the case that what happened to sea turtle young during this stage in their lives was unknown. However in 1987, it was discovered that the young of Chelonia mydas and Caretta caretta spent a great deal of their pelagic lives in floating sargassum beds - thick mats of unanchored seaweed floating in the middle of the ocean. Within these beds, they found ample shelter and food. In the absence of sargassum beds, turtle young feed in the vicinity of upwelling 'fronts'. In 2007, it was verified that green turtle hatchlings spend the first three to five years of their lives in pelagic waters. Out in the open ocean, pre-juveniles of this particular species were found to feed on zooplankton and smaller nekton before they are recruited into inshore seagrass meadows as obligate herbivores.
Sea turtles used to be hunted on a large scale in the whaling days for their meat, fat and shells. Coastal peoples h
If you want to link to this article then please use this URL: www.sail-world.com/39094