Habitat Directive: Priority species. Annex II and IV. MED state of conservation: “unfavorable-inadequate” (2013-2018).
IUCN Red List: “Vulnerable” at global level, with declining trends. In the latest IUCN assessment, dated 2015, the Mediterranean sub-population was rated ‘Least Concern’ because, thanks to intensive conservation efforts over the last 40 years, the number of nests in the main nesting sites of the eastern basin is increasing. However, this positive trend can only be maintained over time with a continued implementation of efficient and rigors conservation measures. The regional report done by the Marine Turtle Specialist Group in 2020 estimates the number of nets laid annually in the Mediterranean at over 5,700.
It is, by far, the most common sea turtle in the Mediterranean, present throughout the area, even in the northernmost latitudes. In Italy, the nesting area is very wide, but the main sites are in the Ionian part of Calabria and in Sicily, mainly in the southern sectors. Recently, the number of nests surveyed increased, mainly in Campania. In 2021, 57 nets were identified and protected. The main development and feeding sites are in the Adriatic, the Ionian Sea, the Sicilian Channel and, a relatively recent discovery, in the waters of the central-southern Tyrrhenian Sea.
How to recognise it at sea
Size: in the Mediterranean, adults can reach a carapace length of 80 centimetres and a weight of between 50 and 70 kilograms.
The carapace is red-brown, with 5 pairs of vertebral shields and 5 pairs of costal shields, while the plastron is yellowish. The head is very large, proportionally larger than other sea turtle species, with powerful jaws that it uses to crush bivalves and other organisms on which it feeds. Two pairs of pre-frontal plates are present. Juveniles have a notched dorsal hull that disappears with time. As in other sea turtle species, sex can only be distinguished in adults, with the male having a more developed tail and longer forelimb nails.
It is an opportunistic carnivorous species that changes its diet during its development. During its first few years of life, spent in the open sea, occupying mainly the surface layer of the water column (epipelagic environment), it feeds on small organisms it finds in floating patches. Subsequently, having reached a length of around 35 centimetres, it moves to the coastal area to feed on molluscs, echinoderms and other not very mobile animals that populate the shallow and sandy seabed. The transition is not, however, definitive: common turtles, in fact, repeatedly throughout their existence may alternate between phases of coastal life and others pelagic life.
It is a skilled swimmer, capable of diving to depths of 150-160 metres, and is able to memorise the richest food spots and return to them even after years.
Mating occurs in spring, with females then migrating to nesting beaches in the same area where they were born (philopatry). The peak of the breeding season is between June and July. It lays up to 150 eggs in holes dug in the sand. The incubation period depends on the temperature and, on average in the Mediterranean, is around 50 days. It is always the temperature of the sand that determines the sex of the brood (warmer ones will produce proportionally more females). The age at which they reach sexual maturity is not yet certain, probably around 20-25 years.
- In the past, it was thought that Caretta caretta spent a period in hibernation, due to the few sightings in winter. Today, however, we know that when temperatures drop, the caretta can dive for up to eight hours, only returning to the surface briefly to breathe.
- During the resting phase in the open sea, the caretta expands its lungs to the maximum, floating with its carapace exposed to the air. This increases the risk of collision because, if frightened, the turtle cannot dive quickly.
- Caretta are skilled navigators, able to memorise the location of their home beach or feeding sites and return to them even after dozens of years with good accuracy
- To break the shell, the hatchlings use a special structure, the ‘egg tooth’, which is then reabsorbed within a couple of weeks