Who are the critters out at those in-between hours?
Most of us are familiar with two of the terms for periods of activity in plants and animals: nocturnal and diurnal. Nocturnal animals like bats are active at night and diurnal animals like humans are active during the day. But there’s another major category for activity for animals and that’s crepuscular.
Crepuscular, a word drawn from the Latin word for "twilight," is a term for animals that are active primarily at dawn and dusk. There’s a very smart reason for picking these dimly lit in-between hours to be active: crepuscular critters are avoiding predators. Many predators are most active at the peak hours of daylight and darkness, so animals like rabbits which are a prey species for countless carnivores, are active during twilight hours when predators are already tired from a night of hunting, or are just waking up. Plus, it’s tough to see during these hours, a fact that gives prey species an added edge in hiding from or escaping predators.
In hot areas, there’s another reason for crepuscular activity: it allows animals to be active when the temperature is most reasonable. Desert animals can escape the heat of midday and the chill of midnight by being active at dawn and dusk instead. And some species may shift from being nocturnal or diurnal to being crepuscular due to environmental factors such as competition with other species — for example, some owl species may be crepuscular to avoid competition with other raptor species — or disturbance from human activity.
Crepuscular activity is further broken down into matutinal animals, which are most active in the morning, and vespertine animals, which are most active at dusk.
The domestic house cat is a great example of a crepuscular animal, as are rabbits, deer, some bat species, bears, skunks, bobcats, possums and many, many more species.