thermia when stress is experienced (McGlone and Pond, 2003). These animals become warm and red-skinned during stress and develop muscle tremors and an inability to walk. In some instances, animals may die as a result of malignant hyperthermia.
Behavior can affect the thermal experience. The stocking density of birds within the transportation crate may inhibit or encourage thermal regulating behaviors, such as stretching and fanning wings during heat episodes or huddling close to other birds under cold conditions. Posthatch-fasted male chicks held in shipping containers exhibited dispersal behaviors at 35°C (Xin and Harmon, 1996), and birds transported at high densities during hot weather are more prone to heat stress (Schrama et al., 1996). As chicks were subjected to lower temperatures, huddling became more evident, and the most huddling occured at 20°C (Xin and Harmon, 1996). Those behaviors also altered moisture production within the container; there was more moisture loss from animals as they spread out at higher temperatures.
Safe temperature ranges for transportation are more difficult to establish for poikilotherms such as reptiles and amphibians. In poikilotherms, a decrease or increase in body temperature of a few degrees is not a cause for concern. Animal activity and alertness may be better indicators of comfort temperature than body temperature (which varies considerably with air temperature).
A major factor that can influence an animal’s effective environmental temperature is the nature of its transportation cage. Transportation containers for small research animals (such as rodents and chicks) are almost always stacked. That feature potentially restricts air flow into or around the containers and can increase the temperature in a container to exceed that of the surrounding environment. For example, when a commonly used commercial chick container was stacked six high in four stacks with 2.5 cm of vertical distance between containers and 5.1 cm between the stacks, the temperature inside the containers was about 5.5 to 10°C above the ambient temperature (Tanaka and Xin, 1997). The IATA Live Animals Regulations (Container Standard #84) and the Animal Welfare Act (9 CFR 3.14(c)(2), 9 CFR 3.36(a)(6), 9 CFR 3.61(a)(5), 9 CFR 3.87(c)(2), 9 CFR 3.137(a)(5)) provide guidance on using spacers or projecting rims in order to prevent obstruction of the ventilation openings and provide space for air circulation.
Transportation containers with biocontainment filters can similarly restrict air flow into a container, increasing the container temperature. In some facilities, rodent transportation caging is autoclaved for reuse. It has