Nature Notes – Ascension turtles

26 January 2022

Conservation

Worldwide there are seven species of marine turtles, four of which have been recorded in Ascension waters. The most numerous turtle found in Ascension is the green turtle (Chelonia mydas). Historically, green turtles in Ascension were extensively harvested for their meat, which caused a catastrophic decline in their population. All turtles have been protected by law in Ascension since 1944 and since then there has been a strong recovery in the species; resulting in the thousands we see nesting on our beaches today. Find out more about all four species recorded in Ascension waters below:

Green Turtle (Chelonia mydas)

Average Weight: 110 – 190kg

Average Carapace Length: 83 – 114 cm

Diet: Herbivore – Sea grass and algae

Status: Endangered

The only species to nest on Ascension’s beaches, green turtles are present around the island between December and July. Returning from their feeding grounds in Brazil over 2,000km away, each female comes to Ascension every three to four years to mate, and lays on average six separate clutches of eggs. It is estimated 7,500- 30,000 nests are laid on Ascensions beaches each season. Each nest has an average of 120 eggs and when these hatch the young turtles make a dash for the sea. It is estimated that only around 1% of hatchlings make it to adulthood. Those that reach maturity may live to 80 years in the wild, and will likely return to Ascension themselves to mate and nest.

Hawksbill Turtle (Eretmochelys imbricata)

Average Weight: 46 – 70 kg

Average Carapace Length: 71 – 89cm                                                                 

Diet: Mainly carnivorous – sponges, shrimp and squid

Status: Critically Endangered                                                                                 

In Ascension’s waters most hawksbill turtles are juveniles which use the island to feed. The Hawksbill can easily be distinguished from other turtle species by their small size, prominent bill and brightly coloured shell markings. They were hunted for millennia in huge numbers for the tortoiseshell that was used in many types of jewellery and trinkets. Harvesting hawksbill turtles for their shell nearly drove them to extinction globally and they remain at risk to this day.

Leatherback Turtle (Dermochelys coriacea)

Average Weight: 300 – 500kg

Average Carapace Length: 130 – 183 cm

Diet: Carnivorous – Jellyfish

Status: Vulnerable                                                                                                    

The leatherback sea turtle is the largest of all living turtles and is the fourth-heaviest modern reptile behind three types of crocodilians. Migrating between Gabon in western Africa and the south east coast of America to nest, the route sees a small number passing through Ascension’s waters each year. They can easily be differentiated from other turtles by their lack of a bony shell (carapace). Instead, its carapace is covered by skin and oily flesh. This soft shell helps them cope with extreme pressure at depths of nearly 1200m when foraging. Unlike other turtles the leatherback also feeds in colder waters, mostly on jellyfish, which broadens its range and therefore its distribution around the world.

Loggerhead Turtle (Caretta caretta)

Average Weight: 70 - 170 kg

Average Carapace Length: 80 - 110 cm

Diet: Mainly carnivorous – shellfish and crustaceans

Status: Vulnerable

A rare visitor to Ascension Island, the loggerhead turtle is a similar size to the green turtle. The key difference is the loggerhead turtles large head which holds strong jaws used to crush shellfish, the main part of their diet. One of the largest South Atlantic populations is found along the coast of Brazil. Fluctuating sea currents results in the occasional juvenile loggerhead turtle arriving in Ascension waters where they may be mistaken for juvenile hawksbills. The loggerhead turtle is the world's largest hard-shelled turtle.