Grass snakes are green with well-spaced, vertical black lines on the sides of the body along its the entire length. The most striking feature is a yellow stripe across the top of the body, immediately behind the head, which is made even more noticeable by the broad black border immediately behind it. Unlike the adder, the grass snake has a round black pupil that stands out against the bronze or copper-coloured iris. Slow-worms have red-brown eyes, with round black pupils. About half the entire length of a slow-worm is its tail and, like other lizards, they can shed their tail if they feel threatened. It takes some time for a new one to grow and, given the circumstances in which they do shed their tails, it is probably quite stressful for them. Please do not, therefore, try to pick one up.