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Chamber-cored fibers capture sunlight, gather heat, and retain both to keep the polar bear warm.

The nests of mallee fowl provide warmth for eggs by use of rotting vegetation and an insulating layer of soil.

The wool of Merino sheep forms an insulating layer via underhair that creates hundreds of trapped air pockets.

Feathers of penguins trap air to retain warmth by being filamentous and forming a continuous layer around the body.

The stems of cushion plants protect from the cold via tight packing.

Bodies of skipjack tuna stay warmer because of counter-current heat exchange system.

The vascular lining in the trachea of adult leatherback sea turtles helps them maintain body temperature while foraging in cold water via counter-current exchange.

By making their hairs stand up, numbats expose more skin to the sun and create an insulating layer of air to reduce heat loss.

Groups of emperor penguins use social huddling to protect themselves from the cold.

Flight muscles of the western honey bee warm the brood nest by contracting without wing movement and transferring heat to brood cells.

The blubber of the bottlenose dolphin absorbs heat by acting as a phase change material

The coat of a reindeer insulates against polar cold with the help of dense underfur that traps air.

Fat cells in ground squirrels generate heat rapidly following hibernation by oxidizing brown fat.

Cells within brown adipose tissues of mammals and birds produce heat by uncoupling of mitochondrial respiration.

The blood vessel network in the tongues of gray whales precools blood to avoid heat loss via counter-current heat exchange.