Blubber is a thick layer of fat, also called adipose tissue, directly under the skin of all marine mammals. Blubber covers the entire body of animals such as seals, whales, and walruses—except for their fins, flippers, and flukes.
 
Blubber an important part of a marine mammal's anatomy. It stores energy, insulates heat, and increases buoyancy.
 
Storing Energy
Energy is stored in the thick, oily layer of blubber. The energy stored in blubber includes both proteins (mostly collagen) and fats (mostly lipids). The ability of blubber to use these stored nutrients means marine mammals are not forced to search for food for long periods of time. Nursing mothers, for instance, build up thick stores of blubber before giving birth. In addition to feeding offspring, mothers cannot regularly search for food. They rely on the energy stored in their blubber.
 
Insulation
Blubber also insulates marine mammals, or helps keep them warm in icy waters. This insulation is necessary. Mammals are warm-blooded, meaning their body temperature stays about the same no matter what the temperature outside is. Keeping a warm body temperature in cold water requires more energy than keeping a warm body temperature in warm water. Some marine mammals, such as sea otters, have a thick fur coat, as well as blubber, to insulate them.
 
To insulate the marine mammal, blood vessels in blubber constrict, or get smaller, in cold water. Constricted blood vessels reduce the flow of blood, thus reducing the energy required to heat the body. This conserves heat.
 
Buoyancy
Finally, blubber helps marine mammals stay buoyant, or float. Blubber is generally less dense than the ocean water surrounding it, so animals naturally float.
 
Animals with the thickest blubber, such as right whales, are found in Arctic and Antarctic regions. In these animals, blubber is more than a foot thick! The thickness of their blubber does not indicate better energy storage, insulation, or buoyancy, however. Those characteristics are determined by the chemical property of the blubber.
 
People and Blubber
 
Many ancient cultures of the Arctic relied on blubber as a staple part of their diet. Muktuk, for example, is a traditional food consumed by the Eskimo and Inuit people, native to the U.S. state of Alaska and the Canadian Arctic. Muktuk is thick slices of whale blubber and skin. Besides being an excellent source of energy and vitamin D, muktuk was often the chief source of vitamin C for these Arctic people. (Citrus trees, whose fruit is probably the most familiar source of vitamin C, do not grow in such cold temperatures.) 
 
Today, the process of biomagnification has made consumption of muktuk and other whale meat a possible health risk. Biomagnification is the process in which the concentration of a substance increases as it passes up the food chain. Blubber's high concentration of toxic substances may be a result of marine mammals' position as top predators in the marine food web. High concentrations of PCBs, chemicals that can cause cancer, and other toxins have been detected in blubber. The concentrations may be natural, or it may be augmented by bioaccumulation of marine pollution.
 
Some countries, such as Japan and Norway, continue to harvest whale blubber for food. Environmental groups have expressed concern about the high concentration of PCBs in the blubber.
 
Whaling
Blubber was the basis of the whaling industry, one of the most lucrative businesses of the 18th and 19th centuries. Millions of whales were hunted throughout the Atlantic, Pacific, and Arctic oceans in sophisticated whaling "factory ships." 
 
After killing a whale and stripping it of its blubber, workers rendered the blubber in enormous iron cauldrons called trypots. Rendering is the process of slowly cooking blubber or other animal fat (such as lard) over a low temperature.
 
As blubber renders, it turns into a waxy substance called whale oil. Whale oil was a primary ingredient in soap, margarine, and oil-burning lamps. Today, some indigenous Arctic communities, such as the Inuit, still harvest blubber and render it for use in traditional whale-oil lamps. 
 
The whaling industry dwindled as petroleum and natural gas replaced whale oil as a major fuel source. Vegetable oils replaced whale oil in margarine and soaps. Environmental laws and hunting limits have slowly allowed whale populations to recover.
blubber
Blubber, right, is a better insulator than coats and jackets, left.

Not All Fat is Blubber
Blubber is different than most types of fat. Blubber is much thicker and contains many more blood vessels than the fat found in land animals, including humans.

Blubber is so unique that many marine biologists don't refer to blubber as fat at all. To them, blubber is a unique type of connective tissue between the animal's skin and its internal organs.

adipose
adjective, noun

animal fat stored in tissues in the body.

anatomy
Noun

structure of an organism.

ancient
Adjective

very old.

Antarctic
Noun

region at Earth's extreme south, encompassed by the Antarctic Circle.

Noun

region at Earth's extreme north, encompassed by the Arctic Circle.

augment
Verb

to enlarge or add to.

biomagnification
Noun

process in which the concentration of a substance increases as it passes up the food chain.

blood vessel
Noun

tubes through which blood circulates.

Noun

thick layer of fat under the skin of marine mammals.

buoyancy
Noun

the power to float or rise in a fluid.

cancer
Noun

growth of abnormal cells in the body.

characteristic
Adjective

particular feature of an organism.

chemical property
Noun

unique identity of a substance expressed by its type and arrangement of molecules.

citrus
Noun

type of fruit tree, including lemon and orange.

collagen
Noun

fiberous protein common in bone, skin, and connective tissue.

concentration
Noun

measure of the amount of a substance or grouping in a specific place.

conserve
Verb

to save or use wisely.

constrict
Verb

to get smaller.

culture
Noun

learned behavior of people, including their languages, belief systems, social structures, institutions, and material goods.

dense
Adjective

having parts or molecules that are packed closely together.

Noun

foods eaten by a specific group of people or other organisms.

dwindle
Verb

to shrink.

Eskimo
Noun

people and culture native to the Arctic region of eastern Russia, the U.S. state of Alaska, Canada, and Greenland.

fat
Noun

material found in organisms that is colorless and odorless and may be solid or liquid at room temperature.

Noun

group of organisms linked in order of the food they eat, from producers to consumers, and from prey, predators, scavengers, and decomposers.

Noun

all related food chains in an ecosystem. Also called a food cycle.

fur
Noun

thick hair covering the skin of an animal.

indicate
Verb

to display or show.

Adjective

characteristic to or of a specific place.

insulate
Verb

to cover with material to prevent the escape of energy (such as heat) or sound.

Inuit
Noun

people and culture native to the Arctic region of Canada, Greenland, and the U.S. state of Alaska.

lard
Noun

fat from animals used to flavor food.

lipid
Noun

one of a large group of organic compounds including fats, oils, waxes, sterols, and triglycerides.

lucrative
Adjective

profitable or money-making.

mammal
Noun

animal with hair that gives birth to live offspring. Female mammals produce milk to feed their offspring.

marine mammal
Noun

an animal that lives most of its life in the ocean but breathes air and gives birth to live young, such as whales and seals.

muktuk
Noun

traditional Eskimo and Inuit meal of frozen whale blubber and skin.

nursing mother
Noun

female mammal who is feeding her offspring on milk she produces.

Noun

substance an organism needs for energy, growth, and life.

offspring
Noun

the children of a person or animal.

PCB
Noun

(polychlorinated biphenal) chemical substance that can occur naturally or be manufactured that may cause cancer.

PCB
Noun

(polychlorinated biphenal) chemical substance that can occur naturally or be manufactured that may cause cancer.

Noun

introduction of harmful materials into the environment.

predator
Noun

animal that hunts other animals for food.

protein
Noun

one of many complex compounds, made of chains of amino acids, that make up the majority of all cellular structures and are necessary for biological processes.

reduce
Verb

to lower or lessen.

render
Verb

to convert animal fats, such as lard or blubber, into an oil by heating it over a low temperature.

right whale
Noun

marine mammal native to the Atlantic and Pacific oceans.

skin
Noun

soft external covering of some animals.

sophisticated
Adjective

knowledgeable or complex.

store
Verb

to keep for future use.

Noun

degree of hotness or coldness measured by a thermometer with a numerical scale.

toxic
Adjective

poisonous.

trypot
Noun

large iron pot used to boil blubber to make whale oil.

vitamin C
Noun

chemical substance important for health. Also called ascorbic acid.

warm-blooded
Adjective

able to keep a constant body temperature.

whale oil
Noun

wax obtained from boiling the blubber of whales.

whaling
Noun

industry of hunting whales.