|Subpecies||B. m. musculus, B. m. intermedia, B. m. brevicauda, B. m. indica, B. m. unnamed (Chile)|
|Niche||Pelagic baleen whale|
|Length||100 ft (30 m)|
|Weight||190 tons (173 tonnes)|
|Social Structure||Complex family groups|
|Range||All oceans besides the Arctic Ocean|
|Average Number of Offspring||1|
|Main Prey Species||Krill|
The blue whale is a large species of baleen whale that is present in almost all of the world’s oceans. This humongous animal can live for up to 90 years and grows to almost 100 feet long, making it the largest animal to have ever lived on earth.
The blue whale is truly enormous, growing to nearly 100 feet long and weighing about 190 tons. Like other baleen whales, females are typically larger than males. This makes it the largest species of animal to ever live on earth. The whale has a long, narrow body towards its posterior and tail. Their skin, after which they are named, is a mottled blue-gray color. They have two large pectoral fins and a large mouth lined with baleen plates used for feeding on krill.
Distribution and Range
Blue whales are present in all of the world’s oceans apart from the Arctic Ocean. They normally move between their summer feeding grounds in the north or south polar regions and then towards their breeding grounds closer to the equator during the winters. However, despite their large size and high level of interest from scientists and the public, information regarding their distribution and movement patterns remains sparse.
One thing is for certain, blue whales need a lot of food to maintain their massive size and their movements are very much driven by this necessity as blue whales are often found in waters where krill are highly concentrated at the time.
Diet and Predators
Blue whales migrate around the oceans in search of a specific type of food – krill. Krill are small, shrimp-like organisms that are part of the plankton. Blue whales and other baleen whales have long plate-like structures in their mouths that they use to filter krill from the water as they swim. A whale will move through large schools of krill with their mouths open, gathering up whatever it can, including water. Then, it will close its mouth and push the water out with their tongues while the baleen plates contain their food.
In order to maintain its massive size, the blue whale must eat thousands of pounds of krill daily. Indeed, during the feeding season, some individuals may consume 4-6 tons of krill each day for several months. In addition to these krill, whales will also capture other small crustaceans such as copepods as well as unfortunate fish. Blue whales travel between productive polar waters in the summer and more tropical regions during the winter where they give birth and nurse their calves, often searching for food along the way.
The adult blue whale faces few natural threats from predators due to its massive size. On occasion, orcas will attack blue whales as a group, focusing particularly on calves. However, once abundant in all of the world’s oceans, by the end of the 19th century, the blue whale was hunted nearly to extinction by whaling fleets. Between 1868 and 1978, 382,595 blue whales were recorded slain. Currently, there are approximately 10,000-25,000 blue whales in the world’s oceans, representing only 3-11% of the original population size.
Blue whales are often solitary but are sometimes found in pairs or small groups. Little is known about their life history, but it is believed that they live for about 90 years and reach sexual maturity at about 5-15 years of age.
The gestation period for blue whales is 10-12 months. Mothers give birth to one calf which she nurses for up to 7 months. The calf is likely weaned while traveling towards their summer feeding grounds but may continue to travel with its mother for several years before reaching sexual maturity itself. Little is known about the species’ life history and breeding grounds, but blue whales and their calves are often observed in the Gulf of California (Sea of Cortez), suggesting that this is one important breeding and calving area for the populations in that part of the world.
The blue whale’s conservation status is often difficult to assess due to limited knowledge of the species’ life history. However, given its slow reproductive rate and various threats from humans and climate change, the species is considered Endangered on the IUCN Red List of Threatened Species.
Blue whales face many known threats. Despite the ban on hunting the species imposed in the 1960s, it still faces many anthropogenic (man-made) challenges. Vessel strikes are relatively common and can injure or kill whales of many species, including blue whales. They are also prone to entanglement with abandoned fishing gear which can reduce their feeding ability, ultimately leading to starvation. Noise pollution in the ocean from human navigations and communications systems is also a threat as it disrupts the whale’s migration patterns and ability to communicate with each other. And finally, like many other species, the effects of climate change are detrimental to the species.
Fun Facts about the Blue Whale!
As the largest animal on earth – even larger than any known species of dinosaur to have ever lived – it is no surprise the blue whale continues to fascinate. Despite relatively little being known about it, there are still many fun facts and interesting biological concepts that can be explored with the species.
With so little being known about the blue whale and its life history, you may wonder how scientists can estimate the species’ lifespan with any degree of certainty. Although there are several ways to do this, one of the most novel, reliable, and fascinating techniques is the use of the animal’s ear wax, known as cerumen.
Throughout the whale’s life, cerumen is deposited in the whale’s ear canal eventually forming long ‘plugs’. These are layered in visible light and dark sections, each indicating a switch in diet between feeding seasons. By counting these layers much like the rings of a tree, researchers can effectively count each year that the whale visited its winter feeding grounds. Each chronologically deposited light and dark layer (lamina) indicates a switch between fasting during migration and feeding, with one set laid down each year. Thus the number of these layers can be used as an indicator of age.
Before the development of earplugs as an aging method, layers in baleen plates were used. However, these wear down and are not as reliable as a metric. Also, estimates were often made by counting corpora albicantia, fibrous masses on the ovaries of female blue whales. These scars record the number of ovulations (or perhaps pregnancies) for the individual and have been used in the past as an estimator of age.
Large and Loud
Not only is the blue whale very large, but it is also very loud. They are known for emitting a series of pulses, groans, and moans in their communications with each other. These are often so loud that may allow them to hear each other from as far as 1,000 miles away under the right conditions. Perhaps unsurprisingly, they also have an excellent sense of hearing.
In addition to communications between individuals, scientists also believe that blue whales may use this powerful vocalization and a keen sense of hearing in combination as a type of sonar-navigation system, bouncing sounds off of the ocean floor and navigating based on their ‘echoes’. This may be a particularly useful ability in the darkest depths of the oceans where light does not reach, making vision largely useless for navigation purposes.
The Biggest of the Big
At about 100 feet long and nearly 200 tons, the blue whale is the largest animal species in the world. However, not all populations and subspecies of blue whales are created equal. In fact, of the five known subspecies of blue whales, members of the Antarctic (Balaenoptera musculus intermedia) populations tend to be even larger than other blue whale subspecies. While most blue whales grow to about 90 feet long, these Antarctic behemoths can grow to about 100 feet long, weighing roughly 170 tons (330,000 pounds).
Besides its size and shape, the mottled skin of the blue whale is also a distinguishing feature. These patterns on the skin of the whale are present on their sides, back, and belly, and are unique to each individual. While the size and shape can usually help to easily distinguish the blue whale from other species of whale, for example, the mottling on their skin can be used to identify individuals within the species or group of whales (pod). This is particularly helpful for researchers of the poorly understood species as it allows them to be confident in classifying their observations of particular individuals.