Many believe Bigfoot are nocturnal and have learned over the years to avoid human beings when possible.
The BFRO suggests that the sasquatch is a predominantly nocturnal animal and its night vision exceeds that of man substantially. It is probable that this increase in night vision is a function of a larger eye and pupillary size rather than a reflecting layer. The animals walk with ease in seeming total darkness, but forage during the day. An indication of their nighttime activity is the fact that they are seen as frequently during the night, if not more often, than during the day, despite the limited sight distance and detection by nocturnal observers.
During nighttime expeditions, many Bigfoot researchers have experienced "eye-shine" coming from these creatures. This "eye shine" is consistent with other nocturnal animals like cats. These animals have a mirror-like layer at the back of their eyes (tapetum of the retina which helps them see better in the dark) that reflects background light like tiny searchlights. Other primates such as prosimians (primitive primates such as the lemur and aye-aye) exhibit such a feature as the tapetum lucidum. What makes this interesting is that great apes do not have this feature, neither does humans. It is worth noting that some humans do possess "a limited eye shine" that can be seen in red eye images in some photographs.
Some researchers don't buy into the Bigfoot is nocturnal idea. Humans and apes do not see in the dark due to a lack of the tapetum (reflective retina), however, Bigfoot’s eyes have repeatedly been documented to have red reflective eyes which points to them possibly having the taptetum so they can see well in the dark (many sightings of these animals do occur during the dark when they are roaming around). Human eyes only shine red when a flash from a camera hits them at the right angle. This is due to blood vessels in the eye and the flash hitting before the pupils have time to constrict.
Finding Bigfoot - Is Bigfoot Nocturnal?
Mike Rugg on Sasquatch Nocturnal activity
[via: BFRO via grandcherokee.proboards.com]