A group of mammals characterized by their activity during the night and rest during the day. These species have adaptations that allow them to thrive in the darkness, often including enhanced senses of hearing, smell, and night vision. They can be further classified by their diet, with some being carnivorous, feeding mainly on other animals. This category falls within the broader classification of mammals, which are vertebrate animals known for their fur or hair and the production of milk by females, and even more broadly, within the kingdom of animals.