We like to think that humans are the most successful animals, but it could be argued that rats are even more successful. Rats are found wherever people live, and they can adapt to live in most environments. The two common types are the brown rat and the black rat. Rats produce up to seven litters per year, each one containing between 6 and 22 young.
Rats are a source of disease, and their droppings frequently contaminate stored food. Black rats were responsible for the spread of the Black Death in the Middle Ages, which killed millions of people in Europe. Rats are very difficult to control because they quickly adapt to the effect of poisons and learn to avoid traps.
Rats are also highly intelligent and are able to exploit new food sources. They climb walls to enter food stores, or tunnel beneath walls, and can even bite through plastic or water pipes in order to drink. They are omnivorous, which means that they can live on almost any edible substance.
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