Dolphins make a variety of sounds, including clicks, squeaks, whistles, and creaking noises. They produce sounds differently in air and underwater. Wild dolphins mainly make sounds underwater, although they have been known to emit high-pitched whistles both under the water and above the surface. Dolphins do not have vocal cords in their larynx, so sounds are probably produced by other means. The sounds that a dolphin makes underwater serve to help them navigate, locate food, glean information about the environment, and to communicate with other dolphins. Clicks are used to sense their surroundings through echolocation, while they use whistles to communicate with other members of their species and possibly with other species too. It is also thought that each dolphin has a unique whistle called a ‘signature whistle’, which is used to identify an individual. Dolphins make sounds in air by releasing air through their blowholes, and they have great muscle control over their blowholes, which allows them to alter the sounds by changing the size and shape of the blowhole opening. At Dolphin Research Center, the dolphins apparently vocalize to get people’s attention as they walk by the lagoons.