Rats, particularly common species such as the Norway rat (Rattus norvegicus) and the Roof rat (Rattus rattus), are opportunistic omnivores. This broad dietary classification means they can thrive on an immense variety of food sources, contributing to their global distribution and population density. Their ability to adapt their caloric intake allows them to survive in environments ranging from wilderness areas to dense urban settings. They exploit human environments efficiently due to their flexibility and a highly developed sense of taste that helps them select nutritionally balanced meals.
The Preferred Menu
Rats are omnivorous, but they exhibit clear preferences for foods that offer the most nutritional value and caloric density. Their ideal diet centers on high-energy sources like grains, seeds, and nuts, which provide the fats and proteins necessary for their fast metabolisms. When given a choice, rats will actively seek out items rich in fat, sugar, and protein, such as cereal grains and fruits.
Dietary tendencies differ between the most common species, reflecting their natural habitats and behaviors. The Norway rat, often found at ground level, prefers protein-rich foods, including meat scraps, fish, and pet food.
In contrast, the more agile Roof rat tends to live in elevated spaces like attics and trees. It is sometimes called a “fruit rat” because of its inclination toward fruits, berries, and vegetables. Both species will consume insects and carrion when preferred foods are scarce, confirming their omnivorous nature.
Gnawing vs. Eating
The widespread belief that rats will eat “anything” often confuses their nutritional needs with a separate, biologically driven behavior: gnawing. Rodents possess incisor teeth that grow continuously throughout their lifespan, a condition that necessitates constant grinding to prevent them from becoming painfully overgrown. This continuous growth means a rat must gnaw on hard materials simply to maintain proper dental length and function.
The act of gnawing is a dental requirement, not a search for calories, which is why rats chew through non-food items that offer no nutritional value. Their powerful jaws and hard tooth enamel, which rates a 5.5 on the Mohs hardness scale—comparable to a kitchen knife—allow them to damage materials like wood, plaster, plastic pipes, and electrical wiring. This behavior is distinct from feeding and is the primary cause of structural damage rats inflict within human buildings.
Key Dietary Attractants
The primary factor attracting rats into human environments is the accessibility of highly concentrated calories. Sources that are easy to access and offer a substantial energy return become magnets for rats seeking sustenance. Pet food, often left out in bowls or stored in unsecured bags, is a significant lure due to its high fat and protein content.
Other major attractants include poorly secured garbage, compost piles, and discarded grease or oils, which provide a reliable mix of proteins, fats, and carbohydrates. Birdseed, in particular, is a concentrated source of seeds and grains that provides an ideal, easily hoardable food supply. Securing all stored food in hard, sealed containers and ensuring trash bins are tightly closed are effective steps to eliminate the easy, high-calorie sources that draw rats near homes.