TURTLE MONITORING IN THE iSimangaliso WETLAND PARK
At Thonga Beach Lodge, during Turtle Season (Nov-Feb) we arrange one turtle drive each evening/night at low tide. Due to the concession legislation we have access to the beach at the low tide mark for 4 hours. We are permitted to drive the length of the beach looking for the females and the hatchlings. There is a charge for the turtle drives but no charge for turtle walks.
The time of the drive may be just after dinner, or maybe in the early hours of the morning as it all depends on the low tide. The drives can last up to as long as three hours.
Although the Turtle Tracking Tours are available from Nov to Feb only there is a good chance of seeing hatchlings in March. Guests taking a walk in the early morning or late afternoon are often rewarded for their romantic strolls with the last of the season’s nests scramble for the sea.
Loggerhead Turtle (Carettacaretta)
Loggerhead Turtles are very much smaller than Leatherbacks however they are the world’s largest hard-shelled Turtle. Their weight range is between 80-200 kg with a length of 70 -95 cm. however, the maximum recorded weight of a Loggerhead was 545 kg with a carapace length of 213 cm.
Loggerhead Turtles have been recorded to the cosmopolitan distribution with the broadest geographical range of all sea Turtles. It inhabits the Alantic, Indian and Pacific Oceans as well as the Mediterranean Sea.
Their average dive duration is 15-30 minutes however researchers have recorded that they have stayed submerged for up to four hours.
Loggerheads spend most of their time in open ocean and shallow coastal waters, they rarely come ashore except for the female’s brief visit to construct nests and lay their eggs.Nesting takes place at night from the end of October through to January. The round, white, leathery eggs – as many as 120 in a clutch – are laid in the sand and then covered with packed sand. The females come ashore and lay up to 500 eggs in 15 days intervals. The juveniles hatch after 55 days and head out to sea.
Loggerhead Turtles are omnivorous, subsisting mainly on bottom dwelling invertebrates. Due to their particular diet, they have a large head with strong powerful jaws to crush their prey. Scale points or claws on the anterior margin of their forelimbs assist them greater with manipulation of their food and the male uses them to hook onto the female whilst mating.
Leatherback Turtle (Dermochelyscoriacea)
Leatherback Turtles are the largest of the Turtles in the oceans of our planet , they are the largest of the reptiles other than three species of Crocodile. The largest recorded length of a Leatherback was 3m from head to tail with a carapace length of 2.2 meters. This particular Turtle weighed in at 916 Kg however typically they are between 250 to 750 Kgs.
They are the fastest moving reptiles and travel vast distances between their feeding grounds and nesting beaches. Scientists have tracked a Leatherback Turtle that travelled 20 000 Km in 647 days. A Leatherback from our Maputuland coast was fitted with a GPS transponder and its journey was recorded to travel from Maputuland to Angola on the West Coast of the African continent.
Out of all Turtles, Leatherbacks dive the deepest. One Leatherback has been recorded to dive 1 280 meters, making them one the deepest diving marine animals. Typical dive durations are between 30 and 85 minutes.
As its name implies, a Leatherback Turtle does not have a bony carapace shell like other Turtles, its back is covered in a dark grey to black leathery and oily skin. Female Leatherbacks prefer soft sandy beaches because of their soft leathery backs. Females will lay as many as 10 clutches in one breeding season, each clutch with an estimated 80-100 soft shelled eggs. Both the Leatherback and the Loggerhead go to great lengths to disguise their nesting sites.
Leatherback Turtles subsist almost entirely on Jellyfish.
Seven species of marine turtles exist in the world’s oceans today, therefore turtles are important indicators of ocean health. There are five species found off the Kwa-Zulu Natal Coast, namely, the loggerhead, leatherback, hawksbill, green and olive ridley turtles. Of these five species that occur in South African waters, only the loggerhead and leatherback females nest along our shores.
Both loggerhead and leatherback turtles nest during the summer months at night (October – March). Steep beach faces makes it easy for loggerheads to swim through the surf over low lying rock ledges. The females emerge from the surf and rest in the wash zone on the beach. Here they assess the beach for any danger by lifting their heads and scanning the beach. Satisified that there is no danger they then proceed up the beach to well above the high water mark.
Having found a suitable site the female commences by excavating a body pit, this enables her to lie with the top of her carapace level with the beach. She then digs an egg cavity with her hind flippers. The egg pit is a flask shaped hole about 50-80 centimetres deep. A normal clutch constitutes 100-120 soft white shelled eggs which are deposited into this hole. When all of the eggs have been laid the female fills the hole with sand and kneads and presses the surface until the sand is packed hard. Once this is done she disguises the nest site by throwing sand with her fore flippers over the nesting area. Leatherbacks can return up to seven times to lay eggs, while Loggerheads return up to four times in a single season.
Loggerhead turtle eggs take between 55-65 days to mature and leatherback turtle eggs take between 65-70 days. Once ready to emerge the hatchlings cut their way out of the egg with a special egg tooth on the end of their beaks. After the bulk of the eggs have hatched the hatchlings start digging at the sides of the nest. The hatchlings will often wait during the heat of the day, until the sand has cooled before emerging and heading to the sea.
From the early 1960’s, concerted efforts were made to enforce legislation banning egg collection and the harvesting of adults. In 1963, under the auspices of the Natal Parks Board, a Turtle Conservation and Monitoring programme was initiated along the north- eastern coast of Kwa- Zulu natal which is now the iSimangaliso Wetland Park.
To monitor and record nesting populations of loggerhead and leatherback sea turtles along the eastern seaboard and simultaneously provide protection of the females during this vulnerable stage on the shore.
The 56 kilometer of beach, north and south of Bhanga Nek, in the iSimangaliso Wetland Park, is the main focus area of the project.
After the incubation period the nest breaks open and the hatchlings emerge – the sex of the hatchlings, like crocodiles, is determined by the temperature within the nest but with opposite results. Females occur between 32-34 ºC and males occur in cooler temperatures. The success rate of the hatchlings is very low. One of the biggest threats is the Honey badger that patrol the dunes for nests. The nest often opens at night to minimize predation by crabs and birds. Once in the sea the hatchlings are at risk from fish and squids. Because of all these factors it is estimated that maybe 2 of each annual nesting survive to become an adult.
|Conservation Status||Critically Endangered||Endangered|
|Diving||Dive to 1200 metres||Dive to 250 metres|
|Back||Leathery skin – no shell||Dorsal Carapace|
|Life Expectancy||35-40 yrs||+ 60 yrs|
|Speed||Fastest Speed recorded 35km/h||Can travel 20km/day|
|Resting||Rest for 1 minute a day||Rests for 3.5 hours a day|
|Food||Jelly fish – can eat body weight daily||Crabs, molluscs, urchins|
|Sea Temperatures||Not effected by sea temperatures due to continual swimming action||Very dependent on sea temperatures – go into lethargy state if too low|
|Habitation||Feeding in cooler waters & warmer regions for breeding – Long distance migration||Juveniles prefer the shallower oceans and floating mats of Sargassum algae – adults prefer open ocean|
|Breeding regularity||Sometimes annually||Every 2-3 years|
|Number of eggs per season||1000 (+-9 nests or 100-120 eggs +-9 days apart)- 85% viable||500 (5 nests of +-100 eggs 15 days apart)|
|Incubation||65-70 days||55-65 days|
|Nesting||Will return to same coastline of hatching||Will return to same beach of hatching|
|Predation as adult||No real predators when adult – apart from man||Man and Sharks – 40% of nesting females seen to have scars from shark attacks|
|Survival Rate||1 in every 1000 survive to adulthood||1 in every 500 survive to adulthood|