Females may produce more than 150 eggs in a single season. In the water, adults eat similar animals, as well as frog tadpoles. On land small slugs, worms and beetles are most often taken as food. Interestingly, the arrangement of these spots is unique to each newt and can be used to identify individuals. As an amphibian the Great crested newt's lifecycle involves both water and land.
Adults enter the water in the spring to breed, with eggs being laid singly on water plants.
At this stage feathery external gills are used to breathe, but these are gradually lost and when the adults emerge from the water they have internal lungs allowing it to live and breathe on land. While adult Great crested newts spend half of each year on land, little is known about their behaviour. Active mainly after dark, they can sometimes be found hiding under logs or stones during the day to avoid dangerous dehydration, because the skin of amphibians is not very waterproof. Completely protected by the Wildlife and Countryside Act, it is illegal to harm or collect these valued creatures and the law has been used to prevent development of important breeding ponds. Despite this, however, pollution of suitable habitats still occurs, as well as damage to the natural habitats around ponds which the adults use while on land.