As the warm weather approaches many people dream of typical summer things - swimming, enjoying a cool breeze and long icy drinks, lying by the pool in the shade - its strange to think that all these symbols of summer are basically coping mechanisms that our bodies use to manage high ambient temperatures.
High temperatures and heat are not the same. Heat is energy and is measured in joules, by removing or adding heat the temperature changes according to specific heat capacity, eg it takes more heat energy to raise the temperature of water than to raise the temperature of air, so water has a higher heat capacity than air.
To cope with ambient temperatures and manage their own body temperatures, animals use complex processes that combine into a function called thermoregulation. Living creatures have their own body heat; endotherms such as mammals regulate body heat by metabolic processes, while ectotherms such as reptiles have body temperatures that track the ambient temperature in the environment.
Physical characteristics and habits of creatures living in certain environments have evolved to assist in coping with conditions. The colour and texture of the body surface effects heat flux through radiation emissivity. In hot climates the sparse hair of tropical animals ensures that heat is conducted quickly from the skin to the outside air.
However bodies must develop ways to cope with changes in outside temperatures. The hypothalamus in the brain works like a thermostat which initiates proportional mechanisms and behaviours once the ambient temperature moves above or below a certain point.
When temperatures increase the body has to dump excess heat. One of the primary methods is to lose heat through evaporation, when liquid water turns to gaseous water vapour heat energy is used and this cools the skin surface. – evaporating 1g of water can cool 585g of body tissue by 1degree C so a 60kg animal which can evaporate 1 litre of water will cool its body heat by 1 degree C. Evaporation can be through sweating or panting. Increased respiration can change blood chemistry by eliminating CO2, to avoid this, panting uses upper respiratory cavities rather than the lungs.
Sweating and panting use water, in arid regions where water is scarce breathing patterns may change; breathing through the nose cools and dries air while breathing through the mouth exhales moist, warm air. Test this by exhaling onto your hand via nose and via mouth.
Apart from sweating and panting, the hypothalamus initiates other mechanisms such as counter current heat exchange through blood flow, dilating blood vessels and behaviour regulation such as inactivity, seeking shade, wallowing in mud or water, drinking and seeking out dark, cool places or locations which receive wind flow. In some cases animals may even become nocturnal or enter a dormant state called estivation.