What is the term for animals active at dawn and dusk?

Crepuscular, from the Latin for twilight - and it covers a great many animals people assume are nocturnal. Rabbits, deer, most cats including the domestic one, mice and many bats are crepuscular rather than creatures of the deep night.

The advantage is a compromise. There is enough light to see by and not enough for a predator relying on sharp daytime vision, temperatures are moderate in hot climates, and the animals that hunt strictly by day or strictly by night are both less active. It is the gap in the schedule.

It explains a set of everyday things. Cats waking their owners at five in the morning and again at dusk are not being difficult; they are on their ancestral clock. Most collisions between cars and deer happen at those hours for the same reason, compounded by headlights being least useful in partial light. And the specialists divide further - matutinal for dawn, vespertine for dusk - which is why the bat genus Vespertilio is named for the evening.