Earth’s largest animal, the blue whale can eat some 4 to 8 tons of krill per day.
ABOUT THE BLUE WHALE
Blue whales are the largest animals ever known to have lived on Earth. These magnificent marine mammals rule the oceans at up to 100 feet long and upwards of 200 tons. Their tongues alone can weigh as much as an elephant.
The blue whale’s heart is the size of a small car and its beat can be detected two miles away. But that’s nothing compared to their calls. Blue whales are the loudest animals on earth and their calls are louder than a jet engine: reaching 188 decibels, while a jet’s engine hit ‘just’ 140 decibels.
Apart from their gigantic size, blue whales can be identified by their relatively small dorsal fin, a fairly rounded rostrum (anterior part of the skull), and approximately 90 ventral grooves, which reach the navel.
They also have row of 300-400 baleen plates on each side of the mouth, which are black in color and range in length from 50 cm in front to 100 cm in back.
Diet of Krill
Blue whales reach these mind-boggling dimensions on a diet composed nearly exclusively of tiny shrimplike animals called krill. During certain times of the year, a single adult blue whale consumes about 4 tons of krill a day.
Blue whales are baleen whales, which means they have fringed plates of fingernail-like material, called baleen, attached to their upper jaws. The giant animals feed by first gulping an enormous mouthful of water, expanding the pleated skin on their throat and belly to take it in. Then the whale’s massive tongue forces the water out through the thin, overlapping baleen plates. Thousands of krill are left behind—and then swallowed.
Coloring and Appearance
Blue whales look true blue underwater, but on the surface their coloring is more a mottled blue-gray. Their underbellies take on a yellowish hue from the millions of microorganisms that take up residence in their skin. The yellowish ventral colouring is due to the accumulation of diatoms (microscopic, unicellular marine algae) in colder water, and has inspired the nickname “sulphur bottom whale”.
The blue whale has a broad, flat head and a long, tapered body that ends in wide, triangular flukes.
Vocalization and Behavior
Blue whales live in all the world’s oceans occasionally swimming in small groups but usually alone or in pairs. They often spend summers feeding in polar waters and undertake lengthy migrations towards the Equator as winter arrives.
These graceful swimmers cruise the ocean at more than five miles an hour, but accelerate to more than 20 miles an hour when they are agitated. Blue whales are among the loudest animals on the planet. They emit a series of pulses, groans, and moans, and it’s thought that, in good conditions, blue whales can hear each other up to 1,000 miles away. Scientists think they use these vocalizations not only to communicate, but, along with their excellent hearing, to sonar-navigate the lightless ocean depths.
Blue Whale Calves
Calves enter the world already ranking among the planet’s largest creatures. After about a year inside its mother’s womb, a baby blue whale emerges weighing up to 3 tons and stretching to 25 feet. It gorges on nothing but mother’s milk and gains about 200 pounds every day for its first year.
Once they have reached about 15 m in length, and are able to follow the normal migration pattern alone. They reach sexual maturity at 5-10 years.
This growth rate is astonishing and is probably the fastest in the animal kingdom. From conception to weaning, it represents a several billion-fold increase in tissue in just over a year and a half.
While researching pygmy blue whales in the South Taranaki Bight region of New Zealand, Leigh Torres used a drone to capture footage of a baby blue whale nursing. This is believed to be the first time that aerial footage has documented the nursing behavior of this endangered marine species.
Blue whales are among Earth’s longest-lived animals. Scientists have discovered that by counting the layers of a deceased whale’s waxlike earplugs, they can get a close estimate of the animal’s age. The oldest blue whale found using this method was determined to be around 110 years old. Average lifespan is estimated at around 80 to 90 years.
Aggressive hunting in the 1900s by whalers seeking whale oil drove them to the brink of extinction. Between 1900 and the mid-1960s, some 360,000 blue whales were slaughtered. They finally came under protection with the 1966 International Whaling Commission, but they’ve managed only a minor recovery since then.
Blue whales have few predators but are known to fall victim to attacks by sharks and killer whales, and many are injured or die each year from impacts with large ships.
DID YOU KNOW?
- When a blue whale exhales, the spray from its blowhole shoots nearly 30 feet into the air.
- Blue whales are the largest animals on Earth. The blue whale is bigger than 25 elephants.
- It is almost twice the size in weight of most large dinosuars, including the Argentinosaurus and Apatosaurus (once mistakenly know as the Brontosaurus).
- Their tongues alone can weigh as much as an elephant. Their hearts, as much as an automobile.
- Blue whales are the loudest animals on the planet – their cries can be louder than a jet engine.
- In one day, a blue whale eats more krill than a African elephant weighs.
- A young blue whale grows at a rate of 90 kg per day.
Current population and distribution
The blue whale has a truly global distribution, occurring in all oceans except the Arctic, and enclosed seas. But despite this, they are one of the rarest of the whales, numbering between 10,000-25,000. Most biologists consider them to be among the most endangered of the great whales.
Only one population, in the eastern North Pacific off California, is showing real signs of recovery and currently numbers about 2,000 animals.
Some of the remaining blue whales are of a subspecies known as “pygmy” blue whales. As their name suggests, they are somewhat less gigantic than “true” blue whales. Until recently, they were thought to be confined to the Indian Ocean region but recent studies indicate they may be more widespread.
Blue whales prefer deeper ocean waters to coastal waters. Populations migrate towards the poles, into cooler waters, in the summer to feed. They migrate back towards the equator, into warmer waters, in the winter to breed. Because the seasons are opposite in the Northern and Southern Hemispheres, the net result of these movements is that the Northern Hemisphere and Southern Hemisphere stocks do not mix.
All oceans except the Arctic, Mediterranean, Okhotsk and Bering Seas.
Argentina, Australia, Bangladesh, Canada, Cape Verde, Chile, Ecuador, French Polynesia, French Southern Territories, Greenland, Iceland, India, Indonesia, Iraq, Japan, Kenya, Democratic People’s Republic of Korea, Republic of Korea, Malaysia, Mexico, Myanmar, Namibia, New Zealand, Nicaragua, Norway, Pakistan, Panama, Peru, Russia, South Africa, Spain, Sri Lanka, Taiwan, Tanzania, United Kingdom, United States, Uruguay
Like other large whales, blue whales are threatened by chemical and sound pollution, habitat loss, overfishing of krill, ship strikes and becoming entangled in fishing gear.
Climate change could also have a major impact on its food supply, since global warming and associated ocean acidification may impact krill populations.
In addition, frontal zones – critical whale habitats – are projected to move further south due to climate change. Frontal zones are boundaries between different water masses, where water can rise from the depths, bringing with it large amounts of nutrients that stimulate the growth of phytoplankton and support substantial populations of prey species for whales.
Blue whales would have to migrate further (perhaps 200-500 km more) to reach and feed at these food-rich areas where they build up reserves to sustain themselves for the rest of the year.
These longer migration paths could increase the energy costs of migration and reduce the duration of the main feeding season. As frontal zones move southward, they also move closer together, reducing the overall area of foraging habitat available.
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