Despite being one of the most common animals on Earth, rats have a surprisingly complex social structure. Rats live in groups called packs, with an average of around ten individuals per pack. This pack is led by an alpha rat, who is often the largest and strongest male in the group. In addition to the alpha, there is a hierarchy of dominance within the pack, which is established and maintained through a combination of aggressive behaviors and non-aggressive social interactions.

Rats communicate with each other primarily through high-pitched vocalizations and pheromones. These pheromones are chemical signals excreted by the rats and are used to mark territory, indicate social status, and send other messages to pack members. Their vocalizations, known as ultrasonic vocalizations (USVs), can communicate a wide range of emotions, including joy, stress, and fear.

Rat packs function as cohesive units. They sleep and forage together, often synchronizing their activities. If a member of the pack is injured, other rats will try to assist and protect it. Additionally, rats have shown the ability to share knowledge among pack members. For example, if one rat discovers a new source of food, it will lead other rats to the food source, illustrating their capacity for cooperative behavior.

The average lifespan of a rat in the wild is about two to three years. Over this time, they are known to reproduce prolifically, with a single female rat capable of producing five litters a year, each containing up to 14 pups. This rapid reproduction rate is one of the primary reasons rats are so widespread and adaptable in different environments.