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==Introduction==

==Introduction==

In order to maintain a constant body temperature as is possible in '''homeotherms''', heat must be transported to the surface of the skin via the blood and released into the environment via conduction, convection, radiation or the evaporation of sweat.  The cooled blood then returns to the body core, thus reducing core temperature.  If heat from metabolism were not removed from the body, the core temperature of mammals and birds would increase by approximately 2.5 C per hour.

In order to maintain a constant body temperature as is possible in '''homeotherms''', heat must be transported to the surface of the skin via the blood and released into the environment via conduction, convection, radiation or the evaporation of sweat.  The cooled blood then returns to the body core, thus reducing core temperature.  If heat from metabolism were not removed from the body, the core temperature of mammals and birds would increase by approximately 2.5 C per hour.

[[image: A seal.jpg|thumb|250px|right|A Seal in water, demonstrating the insulating properties of blubber]]

[[image: A seal.jpg|thumb|250px|right|A Seal in water, demonstrating the insulating properties of blubber]]

If this insulating layer of air is replaced by water, heat is readily lost from the skin's surface, leading to a decrease in core body temperature and ultimately '''hypothermia'''.  The layer is protected by secretions from the skin onto the fur or feathers.  In birds, secretions from the [[The Integument of Exotic Species - Anatomy & Physiology#Avian Skin|uropygial gland]] maintain the water repellant properties of the plumage.  In mammals that are regularly exposed to water, a thick layer of subcutaneous adipose tissue of '''blubber''' is present as the insulating air is completely lost and replaced by water.

If this insulating layer of air is replaced by water, heat is readily lost from the skin's surface, leading to a decrease in core body temperature and ultimately '''hypothermia'''.  The layer is protected by secretions from the skin onto the fur or feathers.  In birds, secretions from the [[Integument of Exotic Species - Anatomy & Physiology#Avian Skin|uropygial gland]] maintain the water repellant properties of the plumage.  In mammals that are regularly exposed to water, a thick layer of subcutaneous adipose tissue of '''blubber''' is present as the insulating air is completely lost and replaced by water.

===Shivering===

===Shivering===

Under moderate heat stress, ruminants pant with a closed mouth.  Under significant heat stress, however, all animals pant with open mouths.  This means that air with a high water content cannot condense on the mucosa of the nasal cavity, thus maximising the heat lost through evaporation.  There is also some evaporation from the oral membranes.

Under moderate heat stress, ruminants pant with a closed mouth.  Under significant heat stress, however, all animals pant with open mouths.  This means that air with a high water content cannot condense on the mucosa of the nasal cavity, thus maximising the heat lost through evaporation.  There is also some evaporation from the oral membranes.