NATURAL ENEMIES
The presence of pets such as dogs or cats makes it difficult for rats to stay in your home or yard. Natural enemies are also stone martens, foxes, owls and other large birds.
NEIGHBOURS AND MUNICIPALITIES
Having rats in your building or yard may have to do with the presence of livestock farms, a recycling park or waterways close by. The city's waste policy can play a role too. If household garbage is incorrectly stored around your house in, for example, poorly secured bins or in loose bags, the chances of having rats around will be higher. In these cases you should contact the municipality and/or a pest control company.
It is also possible that your yard is not the target, but that of neighbors who keep chickens or birds and do not take sufficient preventative measures to scare rats away.
If the rat infestation escalates and no action is taken, you should talk to the neighbors or inform the municipality. They can conduct the conversation for you or together with you and take the necessary steps.