Deer are NOT nocturnal.
Though they may be seen moving about in daylight hours, North American white-tailed deer are crepuscular, meaning they are most active during twilight periods before sunset and after dawn. Research on white-tailed deer demonstrates that observed activity peaks in the final hour before dark. Nonetheless, deer are known to browse plant material well into the night. In the warmer summer months, deer may also increase their activity during daylight hours.
When they are inactive, deer stand or lie down in a protected area. The animals bed down in cover during the middle hours of the day. In addition, throughout the middle portion of the night deer spend some time resting or chewing their cuds while either standing or lying down. Deer spotted walking on or crossing roadsides are usually headed to a feeding area from a bedding location or vice versa.
Gender Differences in Nocturnal Behavior
Furthermore, activity, whether during the day or night, appears to vary according to season and to gender. Typically, females exhibit more daytime than nighttime movement in the spring and summer months. Males have a pattern of greater activity in daylight hours during the spring and increased nighttime movement during the winter.
Nocturnal Behavior and Weather
Some biologists have noted activity patterns related to moon phases and weather fronts. For example, movement is predicted to increase when the moon is full. Storms, on the other hand, reduce the activity of deer. In the hours preceding a storm front, whether nighttime hours or not, and in the hours following a storm, movement slightly increases. Changes in temperature, however, seem to be the most stable predictor of a change in activity patterns. For the most part, the evidence for gauging deer movement by moon phase or weather is inconclusive.