The eyes of most whales are well adapted for life underwater. Strong muscles surrounding each eye change the shape of the eye’s lens. This enables whales to focus their vision both underwater and above water. Whale eyes can withstand high pressure when the animal dives to great depths, and the tear ducts shed oily tears that enhance underwater vision and protect the eyes from the effects of salt water.
The streamlined bodies of whales do not have the external ear structures called pinnae that land mammals use to gather airborne sound. But whales still have excellent hearing and can perceive a wide range of sounds, many of which are not audible to humans. For toothed whales that commonly hunt for food in the dark depths of the ocean, hearing is often enhanced by echolocation, in which the animals emit clicking sounds that bounce off objects. The returning echo is used as a sonar image of the underwater surroundings. Toothed whales share this ability with bats, shrews, and a few kinds of birds.
Baleen whales have a poor sense of smell, and toothed whales lack smell entirely. Some whales, such as dolphins, can taste different chemicals in water to differentiate between sweet, sour, bitter, and salty, but in general the sense of taste in whales is limited.
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