Rats, primarily the Roof Rat (Rattus rattus) and the Norway Rat (Rattus norvegicus), are opportunistic omnivores adapted to human environments. They seek the concealed, protected environment of wall voids and attics for shelter from predators and weather. While these spaces are used for nesting and travel, rats must venture out for sustenance, relying on their senses to locate food and water.
Primary Food Stolen from the Living Space
A rat’s primary diet is acquired through short foraging trips into the home’s living space, not inside the wall. Rats typically leave their nest at night, navigating through walls to access stored or prepared food. They target high-calorie items such as spilled pet kibble, discarded food scraps, and dry goods like grains, nuts, and seeds.
Rats cache, or hoard, food in their wall nests to sustain themselves and their young without constant foraging. They breach poorly sealed containers by chewing through plastic, cardboard, and softer materials. This behavior links infestations to unsealed pantry items or pet food stored near wall access points.
Sustenance Found Directly Within the Wall Void
Rats find supplementary sustenance within the wall cavity when access to the home is restricted. Insects and spiders inhabiting the void space become a source of protein. Rats readily consume these arthropods, including larvae and eggs, especially when preferred food sources are scarce.
Trace nutrients and moisture can also be acquired from the environment. Mold and fungi growth, often accompanying moisture issues inside walls, may be ingested during foraging. Although insulation and wood framing offer virtually no nutritional value, rats may chew on these materials to extract trace elements.
Hidden Hydration Sources
Rats require a consistent water supply and will not establish a lasting nest far from a reliable source. Wall voids can harbor moisture from minor building deficiencies. Leaky plumbing, even a slow drip from a pipe fitting or faulty seal, provides the steady water access needed for survival.
Condensation is another significant source of hydration, especially near HVAC ductwork running through wall cavities or attics. The temperature differential on cold surfaces generates water droplets that accumulate. In high-humidity environments, rats can obtain sufficient moisture from damp building materials, which they may gnaw on to access the saturated core.
Gnawing Behavior Versus Actual Consumption
Much of the chewing noise heard inside walls is not driven by hunger but by a biological necessity for dental maintenance. A rat’s incisor teeth grow continuously throughout its life. The animal must gnaw constantly to wear them down and keep them at a functional length, as overgrown teeth prevent eating and lead to starvation.
This dental requirement means rats chew on almost any material in the wall void softer than their enamel, including non-food items. Common targets include electrical wiring, wood framing, drywall, and plastic plumbing. The resulting damage is a byproduct of dental health, not a search for nutrition, but it often leads to fire hazards and costly water leaks.