Rats are highly adaptable omnivores, consuming a diverse array of plant and animal matter. This flexibility has enabled them to thrive in nearly every environment across the globe, from rural fields to dense urban centers. The specific food sources and nutritional needs of a rat depend significantly on its environment, leading to a contrast between the wild scavenger and the domesticated pet. Rats possess incisors that grow continuously, necessitating a constant need to gnaw on materials to keep their teeth worn down.
Wild Rat Dietary Habits and Scavenging
The diet of a wild rat is defined by its opportunistic nature, prioritizing energy-dense foods that are easy to acquire. In natural settings, their primary diet consists of seeds, grains, fruits, vegetables, and insects, utilizing whatever is seasonally available. They also consume small vertebrates and carrion, though acquiring meat through predation is difficult. Wild rats have a high tolerance for spoiled or discarded foods, allowing them to survive efficiently.
The greatest difference in diet occurs when wild rats inhabit urban areas, where they become proficient scavengers of human waste. Urban rats consume a steady diet of high-quality, protein-rich food scraps, such as discarded meat and processed foods found in trash. This access provides a more stable, higher-quality diet compared to their rural counterparts, who must forage more broadly and compete for resources. Studies show that urban rat diets are more homogeneous and stable, often featuring a higher nitrogen isotope value indicative of a diet rich in animal protein and fat.
Wild rats are notably efficient at surviving on minimal water, particularly if their diet is high in moisture from fresh foods or wet scraps. Despite their ability to adapt, the wild rat’s diet is fundamentally a survival strategy, focused on maximizing calorie intake with minimal energy expenditure. This constant search for sustenance drives their behavior, making them a fixture wherever human activity produces consistent food waste.
Toxic and Harmful Foods to Avoid
Certain common foods contain compounds that are toxic or harmful to a rat’s physiology. One of the most dangerous compounds is persin, found in avocado skin and pits, which can cause respiratory distress and fatal fluid buildup. The toxic alkaloid solanine is present in green potatoes and their eyes, which can lead to sickness if consumed. Raw kidney beans and other dried beans contain phytohemagglutinin, a lectin that can cause red blood cells to clump together and may be lethal.
Other items contain compounds that can cause severe health issues, particularly in male rats. The d-limonene found in citrus fruit peels and mangoes has been linked to kidney damage and cancer in male rats, so these should be avoided. Caffeine and chocolate contain theobromine, which can cause heart palpitations, seizures, and even cardiac arrest. Blue cheese contains a mold that is toxic to rats, and sticky foods like peanut butter pose a physical risk, as they can become lodged in the throat, creating a choking hazard.
Nutritional Requirements of Domesticated Rats
In contrast to the survival diet of a wild rat, the domesticated “fancy” rat requires a balanced diet designed for longevity and health. The primary source of nutrition should be a high-quality commercial lab block or pellet, formulated to meet all of the rat’s daily needs. For adult rats, these pellets should contain 14–18% protein and 3–6% fat to maintain a healthy weight and activity level. This staple diet is designed to be fed freely, ensuring the rat gets consistent nutrition.
Fresh foods serve as supplements and enrichment and should make up only a small fraction of the total daily intake. Safe additions include small amounts of fresh fruits and vegetables, such as peas, berries, or broccoli, which provide fiber and antioxidants. Cooked grains, meat, and eggs can be offered a few times a week to provide protein boosts, particularly for growing or pregnant rats, which have higher protein demands. Clean, fresh water must be available at all times, typically provided through a sipper bottle to prevent soiling.