Animal Spotlight: Blue Whale

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Taxonomy:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Artiodactyla
  • Family: Balaenopteridae
  • Genus: Balaenoptera
  • Species: musculus
  • Average Length: 82-105 ft (25-32 m)
  • Average Weight: 200 tons (180,000 kg)
  • Estimated Average Lifespan: 80-90 years

Blue whales are the largest animals ever known to have lived on Earth. These magnificent marine mammals can live in all oceans of the world, feeding in high latitudes and later migrating to the tropics to breed and give birth. The only one it does not is the Arctic, with a range that extends from the periphery of drift-ice in polar seas to the tropics. It is also absent in some seas such as the Mediterranean, Okhotsk, and Bering. Most individuals will follow a seasonal migration pattern between summering and wintering areas. However, some individuals may remain in certain areas year-round.

There are at least three distinct subspecies: B. m. musculus of the North Atlantic and North Pacific, B. m. intermedia of the Southern Ocean, and B. m. brevicauda (also known as the pygmy blue whale) found in the Indian and South Pacific Ocean. It is possible that B. m. indica, also found in the Indian Ocean, may be another subspecies.

Physical Description:

The blue whale is the largest animal ever known. However, its size substantially overlaps with that of adult fin and sei whales. Like all rorquals, the blue whale is slender and streamlined. The head is broad and U-shaped, like a gothic arch, when viewed from above and is relatively flat when viewed from the side. Along the center of the rostrum, there is a single prominent ridge, which ends in an impressive “splash guard” around the blowholes. The flippers are long and pointed, with the dorsal fin being relatively small and placed three-quarters of the way back from the snout tip. The broad flukes have a relatively straight trailing edge and a prominent notch.

Though the pygmy blue whale has a shorter and a relatively larger head, it is generally not possible to distinguish this subspecies from other blue whales at sea. The blow (or spout) of this species is the biggest amongst all whales, the slender upright column of air rising up to nine meters.

blue-whale
Via Marine Mammal Center

Despite the “blue” in its name, it is only true when in the water. On the surface, their coloring is more of a mottled blue-gray. Their underbellies are somewhat lighter underneath and take on a yellowish hue from the millions of microorganisms that take up residence in their skin. There is a light to extensive mottling on the sides, back, and belly, generally in the form of dark spots on a lighter surface.

Blue whales are baleen whales, which means they have fringed plates of fingernail-like material, called baleen, attached to the upper jaws. The giant animals would 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, leaving thousands of krill behind to swallow. Each individual’s mouth contains 270 to 395 pairs of black, broad-based baleen plates, each less than 1 m long. On the throat, there are 55 to 88 long pleats or grooves that extend from the throat to or near navel.

Blue whales in the Northern Hemisphere are generally smaller than those in the Southern Ocean. The female may be up to 10 metres longer than the male

Diet:

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Blue whales feed on only on prey: krill. Despite their massive size, they will feed exclusively on these tiny shrimplike animals. It is estimated to take 2,200 lbs of food to fill an individual’s stomach. During certain times of the year, a single adult blue whale consumes about 4 tons or 8,000 lbs of krill a day.

This species dives for 10 to 20 minutes at a time and will usually feed at depths of less than 100 meters.

Behavior:

Blue whales live in all the world’s oceans occasionally swimming in small groups but usually alone or in pairs. There has been reports of larger groups of up to 60 whales, probably associated with feeding grounds. However, the blue whale has the most powerful voice in the animal kingdom and its low-frequency sounds can travel in deep water over hundreds, or even thousands, of miles. Under these circumstances, animals which may appear to us to be traveling alone may actually be in constant contact with one another.

These graceful swimmers can cruise the ocean at more than five miles an hour (eight kilometers an hour), but can accelerate to more than 20 miles an hour (32 kilometers an hour) when they are agitated. They often spend their summers feeding in polar winters and undertake lengthy migrations towards the Equator as winter arrives.

To feed, the whales dive for up to 30 minutes, generally interspersed with series of shorter surfacings (at 15 to 20 second intervals). Fluking-up is not uncommon, although not all blue whales are “flukers”. Remarkably, some blue whales have been observed breaching. When feeding, blue whales can be observed lunging, often on their sides or upside-down, through great clouds of the krill to get a mouthful.

momandcalf

There is no set breeding season but calves are born in winter on tropical or subtropical breeding grounds. Females are pregnant for about 11 months and will be pregnant approximately every two to four years, though the interval is decreasing in a response to whaling in order to increase population numbers faster. A baby blue whale is born weighing up to 3 tons and stretching to 25 feet (8 meters).

In its first year, the young will gorge on nothing but the mother’s milk, gaining about 200 pounds (91 kilograms) everyday. To provide the milk, a nursing blue whale mother produces over 50 gallons (200 liters) of milk a day. The milk contains 35% to 50% milk fat, which allows the calf to gain the weight quickly. Just after six months of age, the calf will reach an average length of over 52 feet (16 m) and will be weaned. But before then, the mother and calf will form a very close bond, with the baby swimming close to its mother.

At around 7 to 10 years of age, the blue whale reaches sexual maturity and will mate with several partners during winter and early spring.

Conservation and Threats:

Between 10,000 and 25,000 blue whales are believed to still swim the world’s oceans, representing around 2% to 11% of the total pre-commercial exploitation population. However, blue whales were once abundant in nearly all the oceans on Earth until the beginning of the twentieth century.

Prior to the 1900s, blue whales were too swift and powerful to hunt but with the arrival of harpoon canons, they became a much sought after species for their large amounts of blubber.  Aggressive hunting in the 1990s by whales seeking whale oil drove this species to the brink of extinction. Between 1900s to the mid-1960s, some 360,000 blue whales were slaughtered until they were protected by the International Whaling Commission in 1966. In the end, the total global blue whale population has declined by at least 70% and possibly as much as 90% over the last three generations.

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Hunting was banned in 1966 but some illegal soviet whaling persisted for several years after. No blue whales have been deliberately caught since 1978. Despite decades of protection, they’ve managed only a minor recovery, facing a number of serious threats including ship strikes, noise and chemical pollution, and the impact of climate change. Only in the last few years have there been signs that numbers may be increasing.

All international trade was further prohibited by its listing on the Appendix I by CITES and Appendix I by the Convention on Migratory Species (CMS). Blue whales are also classified as endangered on the IUCN Red List.

To aid in recovery, there are a number of Marine Protected Areas throughout its range as well as whale sanctuaries in the Antarctic, Indian, and Southern Oceans. Several countries have also implemented research and conservation programmes for this species, much of which is coordinated by the International Whaling Commission, and these include identifying areas of critical habitat, investigating species abundance and distribution, and mitigating the threats to the species. IUCN recommends that local measures should be implemented and be required to protect the habitat of specific local populations. This would ensure their long-term viability in the face of increasing human impacts.

 

Interesting Facts:

  • A group of blue whales are known as a pod.
  • When a blue whale exhales, the spray from the blowhole rises nearly 30 feet or 9 meters into the air.
  • Their tongues alone can weigh as much as an elephant (approximately 2.7 tons)
  • A blue whale heart is the size of a Volkswagen Beetle and can pump 10 tons of blood throughout the entire body. A blue whale aorta alone is large enough for a human to crawl through.
  • It is almost twice the size in weight of most large dinosaurs, including the Argentinosaurus and Apatosaurus (once mistakenly known as the Brontosaurus).
  • The blue whale is bigger than 25 elephants.
  • In addition to being the largest animal, it is also one of the loudest animals in existence.
  • Other than humans, the only known natural predator to the blue whale is a pack of hungry killer whales. However, these attacks appear to be rare and rarely successful. Usually, they will go after the helpless young instead of the massive adults.
  • While they migrate, most whales will forgo eating food and live primarily off of blubber, or body fat, and stored calories.
  • The male blue whale is capable of producing particularly long calls, which have been well studied and appear to have functions in sensing the environment, prey detection, communication and male display.
  • 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.

References + For More Reading

NatGeo: Blue Whales

Fisheries and Aquaculture Department: Balaenoptera musculus Fact Sheet

NOAA Fisheries: Blue Whales

Marine Mammal Center: Blue Whales

WWF Panda: Blue Whale

Blue Whale

Arkive: Blue whale (Balaenoptera musculus)

American Cetacean Society: Blue Whale

MarineBio: Blue Whales, Balaenoptera musculus

Blue Whale Facts

IUCN: Balaenoptera musculus

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