The answer to 'what causes rat' is rats are attracted to properties that provide food, water, and shelter. Rats are opportunistic scavengers and will seek out sources of food, such as crumbs, spilled pet food, or improperly stored garbage. They also need access to water, and may find it in leaky pipes, standing water, or pet bowls. Rats also look for warm, enclosed spaces to nest, such as wall voids, attics, or basements.
Rats can cause significant damage to a home by chewing through wires, insulation, and building materials. They can also spread diseases, contaminate food, and trigger allergic reactions. Preventing rats from entering a property in the first place is the best way to avoid an infestation.