The Bones on Blubber

Sometimes used as a byword for “fat,” blubber is actually a unique, miracle tissue—with all sorts of fascinating properties. 

Published December 04, 2019

Marine mammals, like land mammals, store fat under their skin. Like land mammals, they use this vital tissue for energy storage—but that’s where many of the similarities end.

Dolphin in water.

In cetaceans (whales and dolphins), pinnipeds (seals) and sirenians (sea cows), blubber covers nearly every inch of the body in a thick layer, leaving only fins, flukes and flippers exposed. The structure of blubber is different, too—rather than a simple layer of fat cells floating under the skin, as is found in many land mammals, blubber is attached to the skeleton via tendons and ligaments. Blubber is also highly vascularized—supplied with blood by a network of veins—and is filled with stretchy collagen fibers, which help it to maintain shape.

All of these features combine to give marine mammals a fatty tissue layer almost entirely different from our own. It’s more structured, more uniform across the body, and vitally, more blood-filled.

One of blubber’s most important roles is that of insulator. While land mammals also use fat for insulation to a certain degree, they’re rarely exposed to the swift temperature changes that aquatic mammals may experience. As mammals, marine mammals are warm blooded, and need to maintain a constant body temperature. That’s where that veiny blubber comes in! As temperatures plummet, blood vessels in the blubber constrict, reducing surface layer blood flow and thereby conserving heat.

Much like bears stock up before hibernation, by eating as much as possible, so do many marine mammals, especially before the breeding season. Expectant harp seals put on extra blubber—reaching weights of up to 290 pounds—in anticipation of their baby’s arrival. They’ll feed their pups for about 12 days, during which time they won’t eat at all, and will lose up to 6.6 pounds a day. How do they do it? A healthy layer of blubber to draw energy from.

Blubber, which is less dense than water, also plays a vital role in helping marine mammals stay afloat—and agile—in the ocean. The uniform dispersal of blubber across a marine mammal’s body gives it a sort of streamlining, reducing drag in the water. Most importantly, blubber is less dense than water, making marine mammals naturally buoyant.

Marine mammals rely on their blubber to survive. Without this wonder-tissue, specialized over thousands of years in the ocean, they’d be nowhere near as successful at surviving and making the ocean their home. Blubber comes in all sorts of varieties, too—from ½ inch thick blubber on a rough-toothed dolphin, to 12-inch-thick blubber on a right whale!

Many of the rescued seal patients that come into the National Aquarium’s care suffer from the consequences of low body weight and blubber loss. Learn more about our latest seal release and keep an eye out for more seal updates—we anticipate new rescue patients in late January!

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