For a warm-blooded penguin the body temperature is about 39°C
All animals get the necessary energy to maintain their temperature by food combustion
To combust food we need oxygen, which we get through respiration. By human beings, internal organs like liver, kidney, heart and brains,
provide for ¾ from the total body heat, during rest. These heat is constantly carried outwards and released to the environment.
The body temperature remains constant as long as there is a balance between the heat production and heat loss. (see definitions)
Man and animal can regulate their body temperature by choosing an ambient temperature close to the body temperature.
Moreover you can increase or decrease the heat production
; increase by much activity or shivering.
Thermal conduction is strongly affected by the exterior body-layers as fat and skin. By in- or decreasing the blood supply and by arranging hair
(or for penguins feathers), thermal insulation
can be changed.
As for penguins, thermal insulation
is regulated by their feathers and fat under the skin. Their feathers
are tightly packed (see body
) and must regularly be maintained and oiled, to form a waterproof coat.
The downy feathers
form the waterproof "underwear", holding air between the skin and the environment
as a first insulation.
On land, a penguin can increase this insulation by setting up his feathers.
On windless days the surface of a penguin is not warmer than the ambient temperature, so snow will remain there without melting.
Instead of heat loss, the snow will screen from icy wind and avoid a too large heat-interval. But this is not always enough, and
therefore a penguin has to increase the heat production by strong movements with the flippers or shivering.
During diving, the feathers are pressed together by the pressure of the water, narrowing the air layer.
You can now see the typical air bubbles
(bells) coming out of between the feathers.
Now the fat and the skin
have to take over the function for the thermal insulation.
The skin for an emperor and an adelie penguin is 0,4 cm and the fat up to 2 cm thick.
Moreover they are very active and fast in the water and their muscles produce enough heat to keep their body temperature steady.
These heat is probably also used for warming up the caught food from 0°C to body temperature.
Body temperature of a penguin is not as constant as for a human being and can change till 3°C up or down.
Iced water has a much larger (25 times more) thermal conduction
as the Antarctic air, so that, with the same temperature,
a penguin either can stay one minute in the water or rest 25 minutes on land. The heat loss in both cases is the same.
Amazing is also that chinstrap penguins can rest in the water. How they do not freeze that way, is still unknown yet.
As soon as penguins get out of the water, they start cleaning and combing their feathers. With their bill they go with
uniform motions through their feathers and shuffle their head to remove the water.
Their neck is so mobile they can reach almost every single place.
After each motion they bring their bill to the preen gland
, an double-sac organ as large as a pea,
located on the back near the base of the tail, in which a waxy oil is found.
"The secretions of the preen gland empty to the skin surface through one or more nipplelike pores.
Most birds preen by rubbing their bill and head over the preen gland pore and then rubbing the accumulated oil over the feathers of the body
and wings and the skin of the legs and feet. The oil is thought to help preserve the integrity of feather structure and,
in some species, is also believed to be useful in preserving the horny structure of the bill and the scales of the legs and feet.
It has also been speculated that, in at least some species, the oil contains a substance that is a precursor of vitamin D.
This precursor substance is thought to be converted to vitamin D by the action of sunlight and then absorbed through the skin."
(Source : "Preen gland" - Britannica CD. Version 97. Encyclopaedia Britannica, Inc., 1997.)
This oil prevents dehydration and acts as insulation against the water. It also is a "dirt-antidote" and prevents mildews,
bacteria or algae to clutch at the feathers.
The air between the feathers and the skin isolate so much that a penguin could overheat
in the sun.
When they move fast through the colony and the sun burns on their black feathers, the heat can't be lost fast enough.
You can see them spreading their wings
to increase the body surface. Some species even pump blood
through their wings, and then you can notice a pink surface on the inside.
This is almost the only part of the body which isn't covered with feathers, therefore almost the only way to lose heat surplus.
When this still isn't enough, they will pant
like a dog and lose heat through a moist mucous membrane.
The four species of the Spheniscus
, which live in warm climate regions, all have extra bare (no feathers),
pink parts around their bill, to lose heat.