Blue sharks, also called "wolves of the sea", can grow up to 4 metres and weigh between 130 and 230 kilograms. They usually swim in packs. These seemingly lethargic swimmers feed on fish and cephalopods. Blue sharks find their prey with the help of a special sensory organ, the so-called "ampullae of Lorenzini". This sensory organ perceives electric fields that are created by all the animals in the water. Blue sharks can hunt and consume their prey until they grow very old because their teeth are arranged in rows and are replaced by new ones on a regular basis. In general, sharks grow and lose approximately 30,000 teeth in the course of their lives. Females have a skin three times as thick as the skin of males and bear 25 to 100 pups in their lifetime.