Even though you can see deer during any time of day or night, deer are mostly crepuscular animals. They tend to appear most commonly at dawn and dusk.
All deer species, including white-tailed deer, display some degree of nighttime and daytime behavior, so they’re not exclusively crepuscular. However, they’re most active at dawn and dusk because this is the most comfortable time of day for them.
Are Deer Crepuscular?
While the behaviors of deer vary due to seasonal and environmental facts, research does tend to support the idea that deer are crepuscular. This means they’re most active at dawn and dusk.
According to research conducted on Arizona white-tailed deer, Hayes (1992) found:
“My data indicate an increase in activity within the hour preceding sunrise in all seasons, and highest activity during the hour after sunset in 3 seasons.”
In other words, deer are most active:
- Just before sunrise
- Just after sunset
This is textbook crepuscular behavior. The hours before and after sunrise and sunset usually have low light conditions, but are bright enough for animals to still see. These are the ‘twilight hours’.
The one season (summer) when deer seemed to be less active after sunset was Spring, when a dry heat lingered into the evening, which led deer to exhibit some nocturnal behavior.
A 2013 study of roe deer out of Europe also challenges the idea that deer are active just before sunrise. It found that in winter, deer effectively ‘sleep in’ to avoid the coldest time of the day:
“Red deer (Cervus elaphus) also showed the lowest activity levels in winter just before sunrise, which was the coldest moment of the day.” (Pagon et al, 2013, p. 779)
Nevertheless, the study did find that deer woke with the sun and were very active in the early daylight hours, supporting the near-universal consensus that deer are, generally, crepuscular.
Why are Deer Crepuscular?
Deer are likely crepuscular to avoid extreme weather conditions, but not to avoid predation.
Most studies of deer sleep patterns have concluded that deer change their sleep routine based on environmental conditions.
They sleep at night in winter when the cold weather imposes itself on them. Further, they often choose to be active at night in summer when the nighttime hours provide relief from the daytime heat.
Thus, dawn and dusk appear to offer a goldilocks effect. It’s not too hot and not too cool, allowing deer to graze in relative comfort.
However, deer probably don’t choose dawn and dusk to avoid predation.
In fact, wolves hunt most at dawn and dusk. This may be because low-light conditions help them hunt, as well as the fact most ungulates are crepuscular, so they know their prey will be active during those hours.
So, deer, on the whole, prefer the crepuscular hours for environmental reasons.
Are Deer Nocturnal?
While most deer appear to be crepuscular, there is considerable variation in their behaviors. This means that they can be found at all times of the day, including at night.
A study by Hayes (1992) of white-tailed deer in Arizona found that the deer in the study did exhibit some nocturnal activities in spring and summer. The research finds:
“Nocturnal activity was greatest in spring and summer, and decreased in winter.” (Hayes, 1992, p. 7)
Hayes’s study took place in the heat of Arizona and found that heat (as well as other environmental conditions) had a big impact on the deer’s behaviors.
Spring and Summer, where it can get extremely hot throughout the day, were the times when nocturnal activity was most common.
Nocturnal activities during warmer months highlights how strong the impact of temperature is on deer’s sleeping patterns.
A 2013 study in Europe supported Hayes’s findings that deer are not nocturnal in winter. They find:
“The levels of nocturnal activity were lowest in winter; this might indicate the necessity to lower energy expenditure during winter nights, these being the coldest period of the year.”
Furthermore, nocturnal behavior of deer increases during hunting season. This study found that deer in hunting zones are more active at night and stick to thick shrubs to avoid hunters:
“During the hunting season, deer avoided clearcuts, young pine plantations (4–10 years old), and other open habitats and preferred swamp and mature pine forests, both of which provided cover. These results suggest that deer responded to hunter disturbance by moving away from roads and increasing nocturnal activity.”
Are Deer Diurnal?
According to most scholarly articles, deer are awake at least part of the day, meaning they do show some diurnal activity in addition to their crepuscular activity patterns.
This fluctuation appears to be caused by a variety of variables, including the following:
- Human Behavior
- Both Daily and Seasonal Weather
- Species
- Geographical Location
- Predator Movement
It’s not uncommon to come across deer during the day. And in fact, they appear to be more active at day than night, except during the winter.
Deer have ‘diurnal home ranges’. These are the ranges of land that deer will travel on during the day. Their diurnal home range is larger than their nocturnal home range, indicating that they are somewhat more active at day than night.
In other words, they show more diurnal activity than nocturnal activity, but overall, still have highest activity in dawn and dusk.
Do Deer Sleep During the Day or at Night?
Research shows that deer sleep throughout both the nighttime and daytime hours, while being most active at dawn and dusk.
Supporting the idea that deer are crepuscular, many studies like this one have found that deer have peaks in inactivity (e.g. naps or sleeping) twice a day: midday and midnight.
According to Hayes’s (1992) research of white-tailed deer in Arizona, deer do appear to sleep most commonly at night. Hayes summarizes a range of different studies that all indicate that deer sleep most at nighttime, as outlined below.
| Study | Location | Species | Peak in Inactivity (Sleep) |
|---|---|---|---|
| Montgomery (1963) | Pensylvania | White-Tailed Deer | 4-8 Hours after Sunset |
| Georgia, Kammermeyer & Marchinton (1977) | Pennsylvania | White-Tailed Deer | 10pm to Midnight |
| Eberhardt et al. (1984) | Washington | Mule Deer | Midnight to 2am |
Thus, while deer sleep both during the day and night, they mostly sleep at night.
When are the Deer Most Active?
Deer are highly adaptable in terms of their resting and activity schedules. They can also engage in increased diurnal and even nighttime activity. But year-round, they are still most active during twilight hours.
Twilight hours occur immediately before the sun sets in the evening and just after the sun rises over the horizon (but is not yet visible) very early in the morning.
Deer herds will alter their resting and activity habits in response to seasonal and daily changes in weather and human activities, while still remaining most active at dawn and dusk.
Read More: How Big can a Deer Herd Be?
Are Deer Active at Night During a Full Moon?
There is conflicting research data on this. Most studies find that deer are in fact less active during a full moon because they’re aware that the light of the moon increases predator activities.
Pagon et al. (2013) summarize:
“moonlight was actually recognized as an important factor in reducing the activity levels of nocturnal prey species in response to the presence of natural predators that tend to adjust their temporal hunting patterns to the times when preys are most vulnerable.”
In other words, deer appear well aware that predators are out to get them during full moon, so they retreat into the bushes to hide.
This supports other research mentioned earlier that shows deer stick to darkness during human hunting season to avoid predation.
How to Avoid Hitting a Deer at Dusk
Unfortunately, deer often jump in front of cars. When driving during these twilight periods, it is essential to be prepared to stop at short notice.
Because whitetail (and many other deer) are crepuscular, they are most active during the crepuscular hours when humans have a more challenging time seeing them.
So, at dawn and dusk, remember to:
- Watch your speed, especially around blind bends
- Slow down when passing deer, remembering that they often run into cars, not away from them
- Be vigilant to the need to break suddenly
- Do not swerve off the road to avoid deer as this can put you in higher danger.
More Articles About Deer:
Conclusion
While it is natural to assume that deer are nocturnal due to their frequent sightings near highways in the dark, deer are predominantly crepuscular, and the majority of deer are not nocturnal.
During the summer months, they do increase nocturnal behavior to avoid hot weather. When the colder months arrive, they sleep more at night. Nevertheless, deer can be awake at all hours, and in general, we know they are most active at dawn and dusk.
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