Rats eat a wide variety of food. They have voracious appetites and will eat almost anything. They are true omnivorous scavengers, but mostly prefer grain, livestock feed, and meat. Rats have also been known to eat soap, leather, furs, candy, milk, meat, vegetables, poultry, eggs, grain, seeds, fruit, nuts, snails and other rodents. A rat can eat a third of its body weight each day. The rat's main important consumption is water, as it cannot survive long without it. Rats need 1/2 to 1 ounce of water daily.

Two main types of rats, brown rats and black rats eat about the same things. But there are slight differences in preferences between the two. Brown rats or Norway rats eat nearly any type of food, but they prefer high-quality foods such as meat and fresh grain. These rats require 1/2 to 1 fluid ounce of water daily when feeding on dry food. Rats have keen taste, hearing, and sense of smell.

Roof rats or black rats generally prefer vegetables, fruits and grain, and consume 1/2 to 1 ounce food per day from various sources. They do not readily accept meat or fish. They like cereal grains, chopped apples, sweet potatoes, melons, prunes, pineapple, cookies, doughnuts, sweet chocolate candy, peanut butter, and tomatoes. They also consume an ounce of water per day.

Rats are nutritionally a little better than mice. Unlike the mouse that nibbles a little at a time, rats eat much more food in one sitting. Like mice, rats can live in freezers and they love to eat frozen food.

Rats have a habit of gnawing when they eat. Their chewing ability helps them to chew and gnaw through almost anything. They gnaw anything softer than their teeth. They gnaw papers, clothes, wood, plastics, water pipes, electric cables and other building materials. Their habit of gnawing causes immense damage to mankind such as fires, power shortages and flooding.