Nightadapted

Night-adapted is a term used to describe organisms or traits that enable functioning in low-light conditions, especially during nighttime. It encompasses physiological, behavioral, and ecological features that optimize perception and activity when sunlight is scarce. Night adaptation is distinct from diurnal (day-adapted) and crepuscular (active at dawn and dusk) patterns, though some species exhibit flexible activity across these categories.

Visual and sensory adaptations are central to night adaptation. The retina of night-adapted organisms is often rich in rod photoreceptors, which are more sensitive to dim light than cones. This is accompanied by larger or more dynamic pupils and, in many species, a tapetum lucidum that reflects light back through the retina to increase sensitivity. Some nocturnal animals have specialized visual processing or broader visual fields to detect movement in low illumination. Additional senses such as echolocation, antennae, vibrissae, or whiskers can supplement vision.

Ecology and behavior play key roles. Night-adapted species typically forage, hunt, or migrate under cover of darkness to avoid predators, reduce competition, or exploit resources that are unavailable by day. Common examples include owls, bats, and many small carnivores, as well as various insects. Adaptations to dim environments often arise in conjunction with stealthy movement, silent flight, or precise spatial orientation.

Variation exists within the concept. Some species are inherently nocturnal, others are crepuscular or seasonally switch their activity. In humans, night adaptation can refer to temporary adjustments in perception under low light, but humans are not inherently night-adapted compared with specialized nocturnal animals.

See also: nocturnal, scotopic vision, tapetum lucidum.