Newborn mice are nursed by their mothers until they are three weeks old, after which they can consume solid foods. Orphaned newborn mice are often fostered by female rats or mice that are nursing their own newborns. Feed captive newborn mice small amounts of goat milk or kitten formula, and typically wean them off milk or formula between three and four weeks of age.
At approximately three weeks of age, wild mice slowly begin pursuing food outside of the nest. Wild mice eat a variety of foods, including seeds, stems, beetle larvae, roaches, grain and caterpillars. Slowly wean captive newborns off fluids with small portions of dry cereal, followed by solid foods, including fruits, vegetables and bread.
Full-grown mice can consume up to 15 percent of their body weight on a daily basis and can go for extended periods without water. Female mice begin breeding at approximately 40 weeks of age. The typical lifespan of a wild mouse is approximately 18 months. In certain cases, captive mice can live up to two years. Wild mice build their nests in trash piles, weeds, cracked cement and cracked rocks. They also build intricate underground tunnels that contain hollow cavities for nesting and food storage.