How exhibits are designed often seems to be the result of a balance between functionality, practicality, appearance, and budget. Architects or building contractors with little animal experience may err by designing an exhibit that has a pleasing appearance but does not offer an optimal living situation for the animals. Some animals, such as California sea lions (Zalophus californianus) have specialized physiology which requires careful planning when designing an exhibit for them. The use of gunite in the construction of an exhibit may render portions of the exhibit unusable to the animals on warm or hot days. The color of the walls may have a pleasing appearance, however some colors are more solar-reflective, and will reflect longwave and shortwave radiation back into the exhibit, causing the exposed and shaded beach areas to exceed the upper critical temperature for sea lions, which is defined as the temperature which requires heat loss for a species1.
California sea lions appear to be limited in their ability to thermoregulate at high ambient temperatures while they are on land. In natural habitats, sea lions use a variety of behavioral options to maintain a balance between heat loss and heat gain. When sea lions are housed in captive situations, their choices of how to thermoregulate may be limited by the health of the animal, the exhibit design and construction, housing constraints imposed on the animal, or social interactions with other animals in the exhibit. During periods of time when ambient temperatures reach over 30°C extra caution should be taken to ensure sea lions do not become hyperthermic. Providing full shade and a constant water spray to sea lions without access to pools may help to prevent hyperthermia. Adding shade to an existing exhibit, and/or altering the gunite surfaces to decrease both the surface temperature and the reflectance of shortwave radiation, as well as designing the interior of the gunite structures to optimize their properties of heating and cooling should be considered to help minimize the thermal burden on the sea lions.1
Other design features should also be considered. Sloping beaches are optimal to allow young sea lion pups or geriatric animals to easily exit the pool. Several separate haul-out areas help to minimize male aggression. A visual block whereby one animal may rest out of view of another may also mediate male aggression during breeding season. And a design whereby the public cannot drop or throw items into the pool is also preferred.
1. Langman VA, Rowe M, Forthman D, Whitton B, Langman N, Roberts T, Huston K, Boling C, Maloney D. 1996. Thermal Assessment of Zoological Exhibits 1: Sea Lion Enclosure at the Audubon Zoo. Zoo Biol. 15: 403-411.