What does the term primary enclosure mean?

The term "primary enclosure" specifically refers to the structure that directly houses an animal in a research or care setting. This includes cages, pens, or stalls where the animals are kept. The definition emphasizes the importance of this enclosure in providing a suitable environment that meets the animal's needs for space, safety, and comfort, essential elements regulated under the Animal Welfare Act.

While an animal facility room pertains to a broader area that may contain multiple enclosures or other facilities, and a nest box is a specific feature within an enclosure, these do not represent the overall concept of a primary enclosure. Similarly, an animal transport vehicle is used for moving animals but does not serve as their primary living environment. Therefore, the choice of a cage, pen, or stall accurately captures the essence of what constitutes a primary enclosure in the context of animal care and use.