50 CFR 14.131 - Primary enclosures.
(a) A primary enclosure that is not open on top shall have air inlets situated at heights that provide cross ventilation at all levels and that are located on all four sides of the enclosure. Such ventilation openings shall comprise not less than 20 percent of the total surface area of each side of the enclosure.
(1) The devices shall not prevent attendants from having access to the mammal to administer care during transportation;
(2) The devices shall be equipped with sufficient padding to prevent trauma or injury at points of contact with the mammal's body;
(3) Slings or harnesses shall allow free movement of flippers outside of the harness or sling;
(4) The devices shall be capable of preventing the mammal from thrashing about and causing injury to itself, handlers, or other persons, but shall be designed so as not to cause injury to the mammal.
(1) A sea otter or polar bear has sufficient space to turn about freely with all four feet on the floor and to sit in an upright position, stand, or lie in a natural position;
(2) A pinniped has sufficient space to lie in a natural position;
(d) A marine mammal may be restricted in its movements according to professionally accepted standards of care when freedom of movement would constitute a danger to the animal or to handlers or other persons.
(e) All marine mammals contained in a given primary enclosure shall be of the same species and be maintained in compatible groups. A marine mammal that has not reached puberty shall not be transported in the same primary enclosure with an adult marine mammal other than its mother. Socially dependent animals (e.g., siblings, mother, and offspring) transported in the same conveyance shall be allowed visual and, when appropriate for the species, olfactory contact. A female marine mammal shall not be transported in the same primary enclosure with any mature male marine mammal.