The blue whale (Balaenoptera musculus) has the distinction of being the largest animal to have ever lived on this planet. Their size is almost incomprehensible, as anyone who has ever seen the life-size model hanging in New York’s Museum of Natural History, pictured above, can attest to.
Whales, known collectively as cetaceans, may be as small as dolphin-sized pilot whales, but this seems to be the exception. These mammals as a group tend towards the larger size. There are two reasons this growth is even an option for these animals. One is the comparative weightlessness provided by ocean water, eliminating the need for a skeletal structure large enough to support their weight, as a land animal would need to have.
The second is a source of food, in the form of shoals of fish, krill and plankton, whose population density simply does not have anything comparable like it on land. Although it is true that some whales, particularly bowhead and right whales, do feed on plankton, the importance of these tiny plants and animals to whales is generally overrated. Most of the larger species of cetaceans require something more substantial than plankton. For humpback whales this need is satisfied by the huge shoals of herring, anchovies and sand launce found in the cold waters of their feeding grounds.
For the blue whale this nutrition is mainly provided by krill, like the life-sized one pictured here. How many of these tiny crustaceans are needed to sustain a full grown blue whale? Try forty million of them. Per day. Krill are not plankton, although they are pelagic. True plankters are unable to move laterally (although some types, like jellyfish, can control their vertical movement). Krill have swimmeretts that can be used like fish fins and they have full control of their movements.
A full grown blue whale can reach a length of over 100 feet, and a weight of nearly 150 tons (that’s 300,000 pounds!) Krill form large swarms at the surface and schools of them, which are found most highly concentrated in polar waters, are followed by the blue whale during their feeding season. Like most whales, the tiny food is strained from the water using the animal’s baleen. I won’t go into how baleen works here, but you can find all the details in this diary called "Baleen". Here’s a fantastic shot of one of these monsters feeding. Notice the ridges that are used to inflate the throat pouch in order to maximize the number of prey that can be taken in with each gulp.
Like most whales, blues are social animals and communicate using whale song, made most famous by the humpbacks. You can hear a humpback’s song here, courtesy of the Whalesong project. The song of the blue whales are simpler than the complex and repeating notes of their cousins, but the power of this animal’s voice is intense. Their low groans can be heard by other whales up to a thousand miles away. You can listen to a blue whale song here. Pretty impressive, and during mating season these songs may last ten hours or more without rest.
While once quite common, blue whales are now among the most rare species of cetaceans, and there is some doubt as to whether the current population is even high enough to prevent its extinction. There are most likely fewer than 8-10,000 left. This species form families that tend to not interbreed, making their recovery that much more difficult. There are believed to be only about a half dozen families left. One of the problems with estimating their numbers is that, unlike other types of baleen whales, blues tend to be solitary except when the families come together to breed in the fall. The newborns, called calves, are huge, being born after nearly a full year of gestation and weigh nearly three tons at birth. For the first six months of its life it requires up to 150 gallons of milk per day.
As I said, this is not a small animal. Look at the blowhole of an adult above. I’d bet a grown man could fall right into this thing. I’ll end with a very cool link I came across a while back. It’s a life-sized blue whale right there in your browser.
Other diaries in this series can be found here.