A vocabulary of landscape — a landscape of words
1469 entries
nocturnal
A nocturnal animal is active at night and rests by day. The adaptations that go with it are consistent across unrelated groups: larger eyes, a reflective layer behind the retina that gives light a second pass and makes eyes shine in a torch beam, more rods and fewer cones, better hearing, and heavier reliance on smell and whiskers. Most mammals are nocturnal, and the ones that are not are the exception.
Etymology
The word is Latin for belonging to the night. Its counterparts fill out a useful set: diurnal for day-active, crepuscular for dawn and dusk, and cathemeral, a much later coinage, for animals active in irregular bouts around the clock.
Notes
The mammal pattern has a long explanation behind it. Early mammals appear to have been pushed into the night by daytime competition and to have spent a very long time there, which is why the group lost much of its color vision and why primates, including us, had to partly re-evolve it. Some biologists call this the nocturnal bottleneck, and the fingerprints of it are all over mammalian eyes.