Nocturnal and crepuscular animals are particularly vulnerable to welfare harm from artificial lighting that disrupts their natural activity cycles and biological rhythms.
Light cycle welfare is a chronobiological welfare issue that receives little attention in welfare standards, most of which focus on space, enrichment, and social provision. Animals whose natural activity peaks at dawn, dusk, or night are experiencing genuine welfare compromise when managed in conditions that impose human daytime activity patterns. The solution is readily available — reverse-cycle housing, amber-spectrum lighting, and natural daylength simulation — but requires deliberate welfare-informed design rather than the default assumption that animals should be visible to visitors during standard opening hours.