Artificial light at night disrupts the behavior, physiology, and survival of nocturnal species, representing a growing welfare threat to diverse taxa worldwide.
Animals evolved over millions of years with predictable day-night cycles that light pollution fundamentally disrupts. Sea turtle hatchlings that walk toward lights rather than the ocean die from dehydration and predation before reaching the sea. Birds that strike illuminated buildings die from traumatic injury. Insects drawn to lights exhaust themselves in circling behavior and are killed by predators or barriers. The disruption of nocturnal behavior affects feeding, reproduction, and predator avoidance in ways that cause chronic stress and reduced survival.