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but most others have good color vision. Hearing is not an important sense in most reptiles and the internal structures of the ear are usually poorly developed. Most have no visible external structures, apart from a “tympanum” or eardrum which is sensitive to vibrations trans- mitted through the air; these are then conducted along bones to the inner ear and the brain. Snakes have no external ear and can only detect vibrations trans- mitted through the ground.

Only in recent years has modern research been able to disprove the many misguided theories about the reptilian character. Asmost reptiles are predators, they have well-developed sensory systems to help them find their prey and avoid danger. Their eyesight is good, and apart from snakes,whichhaveadifferentmechanism, they can focus their eyes by adjusting the shape of the lens. Nocturnal reptiles like geckoes see mainly in black and white,

Tortoises may appear docile and lethargic, but often this is far from the case. These two male tortoises in the American Southwest desert are engaged in a territorial dispute. This species is only active in the early morning, resting underground during the heat of the day.

The aptly named helmeted iguana occurs from southern Mexico to northern Colombia. An agile and fast-moving species, it uses the skin on the nape in display and to deter predators.

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