Which factor is a standard consideration for lighting design in rodent rooms?

• A. Allow direct sunlight into rooms
• B. Maintain a consistent light-dark cycle
• C. Use bright white light during all hours
• D. Light color is irrelevant to welfare

Answer: (B)

Maintaining a consistent light-dark cycle is essential because rodents rely on circadian rhythms to regulate activity, feeding, physiology, and stress responses. A stable, predictable cycle reduces stress and supports normal behavior, which also helps ensure more reliable experimental results. Allowing direct sunlight introduces fluctuations in light, temperature, and UV exposure that can distress animals and disturb data. Using bright white light continuously disrupts these rhythms and can be stressful. Light color does matter because different wavelengths can influence activity and physiological processes, so it isn’t appropriate to treat light color as irrelevant. In short, a steady, well-controlled light-dark schedule best supports welfare and experimental integrity.