The Lives of SnakesA richly illustrated introduction to the marvellous world of snakes. Descended from prehistoric lizards, snakes have been slithering across the earth for more than a hundred million years. There are some 4,100 species known to exist, and many are venomous, but many more are not. Snakes experience the world in unique ways, smelling the air with their tongues and relying on signs of movement for orientation. They are ectothermic, needing external heat