The Blue whale – The largest animal of our time and the largest animal that ever lived. And yes, that includes Dinosaurs and other Ocean-Giants like Megalodon and Mosasaur. How enormous Blue whales are exactly and how they managed to become so large. 

This is photo of Blue Whale
Image: Blue Whale

Granted, Blue whales are probably not the longest animal of all time. But measuring relative size in length would be somewhat problematic given the various shapes and forms life on earth has already produced. That would lead to misleading statements like: “Pythons are with a length of over 7m or23ft larger than an African elephant” or “the bootlace-worm, with 55m or 180ft – according to the Guinness book – the longest animal in the world, is larger than every dinosaur. When comparing the size of many anatomically different animals, weight is, therefore, the easiest and most fair measurement to use. With that out of the way, let’s begin to visualize just how big blue whales really are. 

Let’s begin with an animal that everyone has seen before – a horse. This gives us a good reference point. Depending on the type of horse the weight of course varies quite significantly, but your typical western horse weighs about 500 kg or 1100 pounds – so about as much as 7 average humans. About twice as big, with a weight of 1 metric ton, is the American Bison, the largest animal in North America. 

Interestingly, of all the land animals the Bison is still relatively closely related to modern whales. They belong, just like the terrestrial ancestors of whales, to the order of even-hoofed animals, so mammals that bear weight equally on two, the third and fourth, of the five toes. Other examples of even hoofed animals are pigs, camels, deer, cattle, sheep, goats, giraffes, and most importantly the Hippo. 

These 1.5 metric ton animals are more closely related to whales than to any land animal. But the largest living land animal is of course the African Bush Elephant. Particularly big bulls with a shoulder height of close to 4 meters or 13 ft. can reach a weight of 8 metric tons: So about as much as 100 humans. Among the extinct animals, notable examples in this weight class are animals like Stegosaurus and T-Rex. But when it comes to sheer size, one extraordinary group dominates – the Sauropods.

This group of herbivorous dinosaurs was by far the largest land animals that ever lived. They include famous examples like Diplodocus, with a length of 27m and a weight of roughly16 metric tons, or Brachiosaurus, which weighs a staggering 35 metric tons. But the largest Sauropods, the Titanosaurs, were once again significantly larger. 

Patagotitan for example was an over 30m long dinosaur with a weight of roughly 70 metric tons. Argentinosaurus, the biggest described Titanosaurs, weight, according to the newest studies, even more than 80 tons making it the largest dinosaur and largest land animal known from uncontroversial evidence.

In the oceans, we have Giants like Killer Whales, which are 6 metric tons roughly as big as an African elephant, and the biggest of the dolphins. This makes them about twice as big as the Pygmy Right Whale. This small whale from the Antarctic is the smallest of today’s baleen whales, the group to which blue whales belong. Roughly 4 times larger is the whale shark, which is similar to baleen whales, and are harmless filter feeder. With a weight of 12metric tons, it is the largest shark, the largest fish, and the largest animal on earth that isn’t a whale, at least today.

In the past, there were of course fish and marine reptiles that were considerably bigger still: Mosasaurus for example. These 15 metric-ton reptiles were roughly 170 times heavier than today’s komodo-Dragon and are the biggest Lizard that ever lived. They were also one of the largest marine reptiles. In fact, only one group seemed to have exceeded them considerably in size: The Ichthyosaurs. The largest described species had a length of 20m or 65 ft, and a weight of 30-40 tons.

Only one animal that lived in the oceans, that wasn’t a whale was still bigger: Megalodon. The largest specimens could possibly reach a weight of 50-60 metric tons, about as much as sperm whale bull, the biggest of the toothed whales. But all these records, on land and in the water, are dwarfed by one animal, and with that, we have finally arrived at the start of this article: the Blue whale. With an average length of 25m or 80ft and an average weight of 110 metric tons, adult Blue Whales are already the largest animals that ever lived.

However, they still can get considerably larger than that. Today, Blue Whales in the southern hemisphere live separated from those in the northern hemisphere. Like their northern relatives, they spend the summer months in the food-rich Polar Regions and feed on the abundant and dense patches of krill found there to build up a thick layer of fat reserves for the winter. At the end of every fall, they begin an up to 5000 km long migration into warmer but less rich subtropical and tropical waters where they breed and give birth.

Because the seasons in the southern hemisphere are offset from those in the northern hemisphere, the migrations of the respective blue whale populations are similarly offset. Southern hemisphere blue whales are generally larger than northern hemisphere animals and females are once more about 6% longer than males. Therefore, if one wants to find an exceptionally large whale, looking for a particularly old and well-fed female in the southern hemisphere at the end of summer is probably the best approach.

The longest whale measured by scientists was a female 29.9 meters (98 ft.) long that weight about 180 metric tons and possibly could have reached a weight of about 210 metric tons during the late summer. The longest whales ever recorded were two females measuring 33.6 and 33.3 meters (110and 109 ft.). The weight of such giants would most likely approach 250 metric tons. These measurements, however, should be treated with a bit of caution at least, as they came from whalers and not scientists.

Additionally, you can’t verify them anymore, as commercial whaling in the last century decimated baleen populations and very probably removed most, if not all, of the super old blue whales out there. In the Antarctic, Ocean Blue whales were hunted until the 1970s, which reduced their population thereby close to 99.9%.

Globally the blue whale population was reduced from 350-400 thousand individuals at the turn of the twentieth century to less than 5000 sixty years later. Even today, more than 50 years after blue whale hunting was banned internationally, they only managed a minor recovery and only a few whales likely now exceed 30m or 100ft in length. Still, even a 30m Blue whale weighs more than:2 Argentionsaurus, 3 Megalodons, 5 Brachiosaurus, 20 T-Rex, 25 African Elephants, 350 Horses, or 2300 average humans. 

One reason that it is so hard to imagine just how large Blue Whales really are probably has to do with the lack of reference points in the ocean. If you were to put a blue whale next to an Airbus-A320, one of the most common medium-range airliners – their size would become a lot more apparent. A similar comparison with the new Tesla Model 3, an NBA Field or the Space Shuttle would make it even clearer – Blue whales are Gigantic.

Of course, such a huge animal can also be expected to have some record-breaking organs. The heart, for instance, is the largest known in any animal. It is big enough that a human could stand in it and weights as much as a horse. With each of its 5-6 beats per minute, it pumps about 500 liters or 130 gallons of blood into the bloodstream.

The aorta that transports the blood through the body is thick enough that a human could squeeze through it and ensures that the roughly 8000 liters or 2000 gallons of blood the whale has reach even the furthest body parts : the penis for instance.On average around 2,5m or 8ft long and 30cm or 1 ft. in diameter it too is the largest in the animal kingdom. In particularly well-endowed individuals can even reach a length of up to 5meter or16 ft and a weight of half a metric ton.

But perhaps the most impressive feature of the Blue Whale is its gigantic mouth which allows it to take in huge volumes of water to filter for food. When feeding, blue whales dive below the surfaces to a depth of one-two hundred meters and then lunge into swarms of tiny krill above them at several meters per second.As they strike, they open their mouths at a wide – almost 90°- angle allowing tens of thousands of liters of prey-filled waters to flow in. 

Dozens of parallel running pleated throat grooves that extend all the way to the belly give the whale the ability to stretch its throat enough to take in its own bodyweight in water – up to 200.000 liters or 50k gallons, Of course that means that, when feeding, the biggest blue whales temporarily weight around 400 metric tons — more than a 747.

Because the giant volumes of water rushing in could potentially rip its jaw apart whiledoing this the whale initially has to actively control the flow of the water with its tongue and certain muscles in its jaw. After the jaws have closed around the engulfed water it uses its giant tongue which alone weighs as much as an African elephant to forces the water out again through a special comb-like structure on the upper jaw called baleen, filtering out everything edible, primarily of course krill. But small fish and squid too are sometimes inevitably caught that way. A human, however, couldn’t be swallowed by a blue whale despite its enormous size as they can’t swallow anything wider than a beach ball. 

The Blue whale’s technique of filter-feeding is called lunge feeding and is one reason for the incredible success of today’s baleen whales. But this technique is only worth the effort when enough prey is available as every lunge costs huge amounts of energy. Because opening its jaws is essentially like opening a big parachute underwater, it grinds the whale to an almost complete halt within seconds. That means for every new attempt Blue whales have to accelerate their massive bodies again, which costs up to 2000 calories. This is also thought to be the reason why Blue whales are only capable of relatively short dives compared to other whales like sperm whales for example.

However, if enough food is available, there is no a better method to ensure quick and easyhunting success. A good catch can yield the whale half a ton of krill – 500 000 calories in one gulp. During a typical 10-minute dive, during which a blue whale makes on average 3-4 of these lunges, it might catch and swallow up to 2.000.000 calories worth of krill or the equivalent of 6600 cheeseburgers. A single dive can therefore provide enough food to cover the whale’s daily energy requirement of 1.5 million calories.

During the summer they typically eat around 40 million krill a day so roughly 3-4 metric tons. These 4 million calories allow the whale to build up the giant fat reserves it needs to survive the winter in the tropics where they breed and give birth but where there is next to no food for them. Even as babies, blue whales are enormous and the biggest in the animal kingdom. At birth, they are with a length of 7m and a weight of almost 3 metric tons already as big as an adult great white.

Since they are mammals blue whale calves are nursed during the first few months of their lives.The milk they drink has a very high-fat concentration of 30-50 % (10 times higher than that of human or cow milk) which gives it an almost toothpaste-like consistency. This has two reasons: On the one hand, it makes feeding under water easier as the milk doesn’t so easily dissolve into the water. On the other hand, it provides the necessary nutrients and energy the calf needs to quickly grow large enough to survive the challenging migrations.

A calf drinks between 200-400 liters of milk a day – that’s around 90 gallons. This allows it to grow at a rate unparalleled in the animal world: Nearly 100 kilos (200pounds) do they gain per day – that’s a whopping 4 kilos or 9 pounds per hour. By the time the calf is weaned, 7-9 months later, it will have reached a length of 15 meters or 50ft and a weight between 20-25 metric tons making it already larger than any other animals that isn’t a whale.

Of course, all these records raise the obvious question why and how Blue whales became so large in the first place

Initially it was believed that it simply mustbe easier underwater to reach such sizes, because ocean animals don’t have to holdup their own weight and that whales therefore continuously grew larger and larger over thecourse of their evolution. However, as we now know, this is not correct. While it is true that the weightlessness under water allows an animal to grow much faster than on land, it isn’t the reason they grow. In actuality it is possibly even more difficult under water to surpass a certain size thresholddue to the lack of said reasons.

Certain body size is of course a strict requirement in marine mammals, primarily because of the increased heat loss under water. Cold water drains heat away from the body 25 times faster than air. Smaller animals are more affected by this because the smaller you are, the more your body surface increases in relation to its volume. Evolving a large round body, paired with a thick layer of fat to insulate it, is an easy way to solve this problem effectively. Beyond that, however, increased size quickly becomes a problem – Especially in the oceans.

The biggest land animals today and in the past were almost exclusively herbivores. Plants make up the lion’s share of the Earth’s biomass – They outweigh humans 10.000 to 1 and account for 80 percent of all biomass, thereby presenting an almost endless foodsupply for large land animals. In the oceans, however, their biomass is comparably small, and most of it is made up of microscopic algae, unusable for large fish or marine mammals. The evolution of a large body underwater therefore becomes a big energy management problem. 

How do you supply the additional body mass with enough fuel?

On land, larger size means protection from predators while plants provide an easy food source to supply the additional bodyweight with energy – ideal conditions to increase in size. In the oceans, however, every large animal inevitably has to become a predator itself. For them an excessive increase in size would more than not create more problems than advantages: That is because, as they grow in length their volume and consequently their energy demand grows exponentially, increasing the food demand similarly. 

At the same time, above a certain body mass, agility and speed start to decrease making hunting more difficult. This paradox usually prevents ocean animals to grow beyond a certain point.The sweet spot for most marine mammals seems to be 500 kg or 1100 lbs and even for large apex predators like sharks, toothed whales, and most marine reptiles from the past a maximum weight of a few tons seems to be the norm. Far from enormous sizes baleen whales can reach. So what made these different? In general, exceptions from this rule are often the result of very specific and unique condition, and are typically based on a fragile balance that can easily be destroyed and therefore often results in an evolutionary dead end. 

In Whales, scientists believe, gigantism is likely the result of two major factors. The first was the evolution of a new more efficient way of feeding – Filter Feeding. Filtering tiny animals in bulk from the water, as all baleen whales do, has one major advantage: Energy efficiency. Instead of having to spend energy hunting a single prey item, the energy that could be wasted if it escapes, blue whales simply glide through dense clouds of krill like aquatic combine harvesters. Due to the small size of the prey, it has no chance of escaping, guaranteeing a successful hunt while keeping the energy consumption comparably low. This makes filter feeding one of the most efficient feeding strategies under water as long as enough prey is available.

Observations of the feeding habits of blue whales have shown that despite the relatively high initial outlay in energy (the result of their massive size), the whales typically regained up to 90-times as much energy as they spend.If a whale swims into a particularly dense swarm it might even recover 1000 times more energy. Such high efficiency is essential to surpass a certain size threshold. It is no coincidence that some of the largest ocean animals today and from the past use this kind of feeding strategy. However, the evolution of filter feeding alone doesn’t explain the whale’s high efficiency when hunting or their gigantism in general. 

Baleen whales first evolved around 30 million years ago and yet their size didn’t significantly change over the next 25 million years. Even when their species diversity drastically increased by 20 mya reaching its maximum of 5 mya, most Baleen Whales were only between 5-10 m or 15-30 ft. in length. In relative terms certainly large, but compared to today’s dimensions rather small. Only during the last 3 million years, roughly with the start of the Pleistocene ice age, baleen whales suddenly began to grow rapidly and up to four times independently from one another. 

At the same time, most of the smaller species went extinct, so today even the smallest baleen whales are quite large compared to the typical whale prior to this event. This suggests that the drastic changes in the ocean’s ecosystem during the last ice age probably caused the gigantism in baleen whales. With the onset of the northern hemisphere glaciation, the oceans began to experience rapid fluctuations in sea levels. drops of 50-100m 150-300ft within only a few hundred thousand years became common and repeatedly destroyed or reduced the shallow tropical shelf areas that previously were the habitat of many baleen whale species.

In addition to that, the final close of the Isthmus of Panama disrupted the water circulation between the pacific and the Atlantic and caused a drastic decline in plankton productivity in the tropics which furthermore impacted the baleen whale population negatively. All these factors likely drove the Caribbean-wide regional mass extinction between 4 and 2 mya that killed among others many of the medium size baleen whale species. 

At the same time, the continuous cooling of the oceans resulted in a global shift in the wind and ocean currents which changed the way water and nutrients were distributed. As a result, intense seasonal upwellings paired with an accumulation of iron dust along the ice shelves produced variable and widely scattered zones of extreme planktonic productivity. Baleen whales had already the right tools to capitalize on this new and abundantly food source. But it required a major shift in their lifestyle: a shift from a more sedentary to a migratory way of life. This sudden need for long-distance migration likely exerted a selective pressure on the remaining whale species to grow larger, as a larger size helps to travel long distances effectively and survive long periods of food scarcity.

So, the recent gigantism in whales is most likely linked to the appearance of a suddenseasonal abundance of widely scattered patches of prey that baleen whales due to their uniquefeeding technique were already able to take maximum advantage of. And once the unique conditions that allowed or required them to grow were actually met, they did so faster than any other group of animals in history. Even if you include the 25 million years during which baleen whales didn’t significantly increased in size, in only about five million generations they increased their body mass 5,000 times. In only 50 million years the terrestrial ancestors of whales that were barely larger than a housecate volved to be the largest animals the world has ever seen.

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