THERMOREGULATORY

ADAPTIONS IN PENGUINS

Vani Jhaveri (V/11/175)

Introduction• Penguins (order Sphenisciformes, family Spheniscidae) are a

group of aquatic, flightless birds living almost exclusively in the Southern Hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have counter shaded dark and white plumage, and their wings have evolved into flippers. Most penguins feed on krill, fish, squid and other forms of sea life caught while swimming underwater. They spend about half of their lives on land and half in the oceans.

• Although all penguin species are native to the Southern Hemisphere, they are not found only in cold climates, such as Antarctica. In fact, only a few species of penguin live so far south. Several species are found in the temperate zone, and one species, the Galápagos penguin, lives near the equator.

Too cold/ Too warm?• Most common beliefs are that penguins need

to find ways to keep warm rather than cool. But the truth is that when on land, the problem most penguins face is how to keep cool.

• To survive long in water, warm-blooded animals must be insulated. Whales have blubber to buffer their body heat from the body of water that would draw it away. Seals have, as well as fat, a thick pelt. But birds - birds have no fur and may have little fat.

So how do they do it?

…

In the Antarctic'sThe internal temperature range of penguins is 37.8°C

to 38.9°C (100°F-102°F).• FEATHERS: Overlapping feathers create a surface nearly

impenetrable to wind or water. Feathers provide waterproofing critical to penguins' survival in water that may be as cold as -2.2°C (28°F) in the Antarctic.

• PLUMAGE: The dark plumage of a penguin's dorsal surface absorbs heat from the Sun, which increases body temperature.

• TRIPOD FORMATION: On land, king and emperor penguins tip up their feet, and rest their entire weight on their heels and tail, forming a tripod, reducing contact with the icy surface, and thus reducing heat loss.

• HUDDLING: During storms, emperor penguins huddle together to conserve heat. As many as 6,000 males will cluster while incubating eggs during the middle of the Antarctic winter

Feathers[Also note: Tucking

of head to cover unfeathered areas of face to conserve

heat.]

Plumage

Resting on heels

Huddling

In the Antarctic’s• RESPIRATORY HEAT EXCHANGE SYSTEM:

Emperor penguins are able to recapture 80% of heat escaping in their breath through a complex heat exchange system in their nasal passages.

• CIRCULATORY HEAT EXCHANGE SYSTEM: To conserve heat, blood flowing to the flippers and legs transfers its heat to blood returning to the heart. This countercurrent heat exchange helps ensure that heat remains in the body.

• MOULTING: During the moult, feathers lose some of their insulating and waterproofing capabilities, and penguins stay out of the water until their plumage is restored to optimal condition. Penguins fast when moulting. Prior to this, they each build up a thick layer of fat to provide energy until the moult is complete.

Moulting

In the Antarctic’s FEW OTHER METHODS:

• To conserve heat, penguins may tuck in their flippers close to their bodies. They also may shiver to generate additional heat.

• A well-defined fat layer improves insulation in cold water, but is not enough to keep body temperature stable at sea for long. Thus penguins must remain active while in water to generate body heat.

In the temperate and tropical regions• NESTING: In temperate regions, penguins (like Yellow-eyed

penguin) avoid over heating by building nests in forest areas, with a good overhead cover of vegetation, providing sufficient shade. In tropical regions, penguins seek shelter from the sun by nesting in burrows or caves.

• FLIPPERS AND FEET: Flippers and the bare feet of penguins that act chiefly as heat radiators. The feathers on the flippers of all penguins are extremely short and provide only modest insulation.

• PANTING: Hyperventilating evaporates body water using up body heat as it does so. Adélie penguins and Yellow-eyed penguins have a circadian rhythm to their panting: it occurs just after mid-day during the hottest part of the day.

• RUFFLING: Penguins can ruffle their feathers to break up the insulating layer of air next to the skin and release heat.

• UNFEATHERED FACE: The faces of many penguins have unfeathered areas to help dissipate heat.

Nesting under forest cover

Nesting in caves

Extension of flippers

Panting

In the temperate and tropical regions

FEW OTHER METHODS:• Little Blue penguin breeding around the coasts

of New Zealand and Australia, go one step further and are active on land mainly at night, usually coming ashore only after sundown.

• Humboldt penguins, found on the coast of Peru and Chile, dig burrows in their own guano: their food eventually recycled as shelter.

• At the equator, the Galapagos penguin, avoids the sun by nesting in cracks in the lava rock derived from their islands' volcanic origins.

Penguin Chicks• Chicks can also be in danger of overheating as on calm days

their down is even more efficient at retaining heat than the feathers of their fathers or mothers.

• The down on the chicks' flippers is not as transparent to heat as the flippers of an adult, and they rely more on their disproportionately large feet to act as radiators.

• On hot days they lie, flippers spread-eagled at their sides, feet exposed.

• Yellow-eyed penguin chicks may even seek out marshy ground and stand with their feet in water.

• Parents of those penguins that breed in the open, shade their young chicks by standing over them.

• As the chicks get older, they are able to regulate their own temperatures and they may move away from the nest.

Parent keeping chick warm

Chick avoiding heat stress

Conclusion• Penguins are endothermic flightless birds who have

adapted quite well to the cold temperatures of the south pole!

• They have special physiological and structural modifications which help them adjust to the changing temperatures whether on land, or at sea.

• They are not only found in the cold regions of the earth but also in few warmer regions like temperate, tropical and equatorial regions.

• For these regions, there are a few other modifications to help retain the cold and not get affected by heat stress.

• Climatic changes are one of the major factors causing deaths in penguins of all age groups, and thus measures should be taken to conserve these beautiful creatures!

Galapagos Penguins

Humboldt Penguins

Yellow-eyed Penguin

Little blue Penguin

Emperor Penguin King Penguin

Thank You!!!