A mouse can survive without food for about 2-3 days if they have access to water. This timeline can vary based on a variety of factors, including the mouse's overall health, age, and environmental conditions. Mice have a fast metabolism and require a consistent source of food to maintain their energy levels. Lack of food not only leads to starvation, but also weakens their immune system, making them more susceptible to illness and infection. It's essential to note that while mice can survive for a few days without food, this is not a humane or sustainable condition for any animal.