Every big city has rats. Some experts say as many as 1.75 rats per person. But, according to the experts, they are essentially unnoticed. However, when the ratio goes higher, they really are noticed. So it is with Paris. There are now about 2 rats per person in the city. They seem to be everywhere, including the Champs Elysées. The city has taken steps, including the closing of nine city parks for a “de-ratting programme”.