A device for retaining an animal within an enclosure includes a harness, a left-side cranial retainer, and a right-side cranial retainer. The harness includes one or more flexible materials and is configured to be selectively secured around a body of the animal. The left-side cranial retainer is coupled to the harness and includes a left-side longitudinal member configured such that a longitudinal axis of the left-side longitudinal member is oriented substantially parallel to a dorsal-ventral axis of the animal in use. The right-side cranial retainer is coupled to the harness and includes a right-side longitudinal member configured such that a longitudinal axis of the right-side longitudinal member is oriented substantially parallel to the dorsal-ventral axis of the animal in use.