How do animals know when it is spring without calendars? They generally look for cues in the environment to perceive the change in season. During winter, the days are shorter and colder. As the season transitions to spring, animals detect that the days have become longer and warmer. What an intelligent way to distinguish between season! It is not only humans that feel more enthusiastic and animated at the beginning of spring. Do you know that animals sense the excitement of this period too? Birds, insects, squirrels, chipmunks and even deer catch the spirit.