Marine mammals are many, such as the dolphins, porpoises and whales, which are seen here during the migration period from December till May. Turtles are a common sight along the coastline of the island. They are a protected species and in the endangered list. It is stated that it will take 15–50 years for this species to attain reproductive age. Though they live in the sea, the females come to the shore to lay eggs and are protected by private societies. Three species of turtles are particularly notable. These are: The leatherback sea turtles which have leather skin instead of a shell and are the largest of the type found here, some times measuring a much as 3 m (average is about 1.5 m) and weighing about 450 kg (jellyfish is their favourite diet); the hawksbill turtles, which have hawk-like beaks and found near reefs, generally about 90 cm in diameter and weigh about 60 kg and their diet consists of crabs and snails; and the green turtles, herbivores which have rounded heads, generally about 90 cm in diameter and live amidst tall sea grasses.