Rats are becoming a big problem in many cities, including London, New York, and Toronto. In one London home, a man found rats inside his flat, which made him worry about his children's health.

Pest control companies say rat numbers are rising because of warmer winters, fast food, less frequent rubbish collection, and overflowing bins. Studies show rat activity has increased as temperatures rise.

Rats breed very fast and often avoid eating poison. Some are also resistant to it. New York even created a special job called "Rat Tsar" to teach people how to stop rats. Experts say the best solution is reducing food waste and keeping cities cleaner.