Whales are often touted as being the biggest living animals on Earth, with the blue whale often cited as the largest animal in Earth’s history. However, not many know how these figures are provided. How do we obtain the size data for such creatures? Is it all malarkey? That is what I’ll be answering today.
Megafauna such as whales, dinosaurs, and many other prehistoric creatures tend to capture the imagination of many by their sheer existence. However, they are often victims of misinformation that even permeated into scientific literature (1). A famous example being the giant squid, which was once commonly stated to have achieved lengths approaching 18 meters in length and weigh as much as a metric ton. It wasn’t until around the past decade did researchers begin verifying the accuracy of recorded specimens and realize that the largest individuals were mainly either unverified claims from the 19th century, specimens that were incomplete, or stretched out beyond their pre-mortem state. Nowadays, it’s generally accepted that the largest giant squids have a total length and mass of ”only” 12 meters and 280 kilograms with the average closer to about 7-9 meters (1). With that in mind, their ”battles” with sperm whales seem more one-sided.
How whale sizes are estimated
But what about the large species of whales? On what basis was it confirmed that the blue whale could surpass 27 meters and 150 metric tons? Well to put it simply, the majority of the existing length and weight estimates the scientific community uses were done using whaling data from the 19th century to the middle of the 20th century. Given the large sample size and how these records tend to span across many decades, they are very useful for comparing temporal and regional size variations of different species and populations. Now length estimates are also corroborated by modern scientific methods on stranded whales and aerial photogrammetry. The total length of a whale is recorded by measuring in a straight line from the snout to the notch within the flukes (1). This length was slightly shorter than the whale’s ”overall” length from the tips of its flukes to the end of the jaw. This convention became standard because the flukes were often cut off by whalers to prevent excess drag as the whale’s carcass was being towed. The jaw was liable to moving around, so the rostrum is used as the anterior endpoint as it could reliably maintain a consistent position.
Weight estimates are largely based on piecemeal weighing. This method required different sections of the body to be cut up and weighed at a time using pressure cookers or dynamometers. By this technique, we also gained the relative tissue compositions of different whales between their blubber, skeletons, muscles, and internal organs (2). However, this estimation systematically underestimates the entire weight of the intact animal due to body-fluid loss from flensing . Comparative whole-body and piecemeal weighing on smaller specimens revealed a potential error of up to 15% in sperm whales (2). These lost fluids account for about 6% of the body weight in baleen whales and 10% in sperm whales (2). By comparison, blood volume alone accounts for about 7% of total body mass across all mammals (3). So it seems consistent to add these numbers when assessing piecemeal weighing of whales. When averaging the masses for individual lengths, a relationship can be derived between body length and the body weight of a whale. The relationship is expressed through regression formulae. This power function is what’s most commonly used for whales.
Body weight= a(Body length)b (2)
Here, ”a” and ”b” are constants that are specific to certain species or regional populations of whales. There’s a limitation to these predicted masses, specifically for rorquals, that will be discussed over in the next section. Nonetheless, these formulae are useful as the heaviest specimens ever weighed are often not the largest individuals ever reliably recorded. This is because even piecemeal weighing was a difficult process and at times are most frequently done for smaller individuals.
Another means for approximating body weight is through oil yields. Masses can be derived from the approximate volume of oil from a whale, converting that volume into blubber weight, and using the ratio of blubber to total weight to calculate the weight of the specimen (4). This data is often useful for estimating historical size trends of depleted populations. While modern methods are useful for evaluating averages, whaling data may still be more valuable for evaluating maximum sizes for these species, as whaling not only depleted populations, but generally targeted the largest individuals, which were often the oldest. Blue whale hunts only ended since the 1970s, reducing the population to less than 1% of its historical size. They currently rest at about 5%. Even with recovery in numbers, younger whales are a much larger demographic than they used to be.
Now with that out of the way, let us evaluate some of the largest whales.
Note: When addressing the average sizes for these individuals, I will be specifically citing the mean sizes at physical maturity. Most casual sources generally report adult size averages that includes sexually mature individuals that are still growing. Generally, it could take an additional one to several decades for a sexually mature whale to stop growing, depending on the species. Hence my earlier point regarding the age distributions of recovering blue whale populations.
The Biggest Whales:
Sperm whale (Physeter macrocephalus): Maximum accepted size- 20.7 meters, estimated 83-88 metric tons.
I will begin with the sperm whale since this species is the most straightforward. The sperm whale is the largest of the odontocetes, the largest extant animal that is not a mysticete, and among the largest toothed-animals in Earth’s history. Sperm whales are the most sexually dimorphic cetaceans, with physically mature males being over 40% longer and twice as heavy as females. Females enter physical maturity at around 30 years of age and average 11 meters and 14 metric tons; they achieve a maximum size of about 12 meters and 20 tons. By comparison, maturity in males occurs as they approach 50 years old at an average length of 16 meters and 43 metric tons (5). Exceptionally large males can grow to 18 meters or longer. The largest individual to be weighed was an 18.1-meter specimen that was 57.10 metric tons (2). When adjusting for fluid loss, the intact animal was most likely at least 63 metric tons. However, this was only the largest sperm whale to be weighed, records exist for even larger ones.
The largest sperm whale within the whaling record was a 24-meter male caught in the South Pacific in 1933 (1). The credibility for this source is challenged since it was such a large outlier and whaling records have been prone to exaggerating sizes for certain individuals due to quotas or measuring errors. Outside of that report, there are records of eight other bulls ranging from 22.08-22.9 meters in length (1). The largest sperm whale that’s widely-accepted by academics was a 20.7-meter bull caught in 1950 off the Kuril Islands (1). This specimen was officially measured using standard techniques and is recognized by Guinness Records. Credibility for sperm whales of comparable length is further supported by jawbones owned by the Nantucket whaling museum (5.5 meters) , the New Bedford museum (5.2 meters), the Natural Natural History Museum in London (5 meters) and the Oxford University Museum of Natural History (4.7 meters). In large males, the jaws consistently measure to about 25% of their total length. These museum specimens likely belong to individuals ranging from 18.8 (Oxford Museum) to 22 meters (Nantucket Museum). Either way, this provides more physical evidence of male sperm whales achieving lengths of 20 meters. In my personal opinion, I doubt male sperm whales could have historically reached 24 meters in length. I believe 22 meters is a more realistic absolute limit, with the 20.7-meter bull being the largest individual we can be certain of. So how much did it weigh?
A regression formula derived from the piecemeal weights of sperm whales from Antarctica and the North Pacific suggests this relationship.
Mass in metric tons (not adjusted for body fluid)=0.0196(Total Length in meters)2.74 (2)
Mass in metric tons (adjusted for body fluid)=0.006648(Total Length in meters)3.18 (5)
There’s an alternative curve, BW=0.00295(TL)3.55 , that’s based on whole-body weights and estimates larger masses for a given length, but it has a much smaller sample size. When using the adjusted formula, the 20.7-meter bull apparently weighed 101 metric tons. I’m assuming the adjustments designed to account for fluid loss don’t work too well when going outside the length range of the dataset (~18 meters). Luckily, the author does recommend that the non-adjusted formula is still viable by manually accounting for the blood loss. When using the non-adjusted formula and adding the 10% of the body weight back in (divide by 0.90), it comes out closer to 88 metric tons. This more conservative estimate feels more realistic. A more recent formula, that’s based on piecemeal weights from Soviet whaling data, predicts the mass to be about 83.6 tons when adding the body fluids (6).
What allowed sperm whales to grow so large is mainly their foraging behavior. Large body sizes are more energetically-efficient for deep dives while also conferring greater aerobic capacity, increasing their submersion times. The other key factor is that sperm whales are the sole predators for some of their deep-sea prey, so they face very little competition from other animals for resources. The tradeoff is that squid may be a lower quality food source when compared to fish and crustaceans, limiting these creatures from being as large as a few other whale species (1). Compared to females, larger males have more varied diets consisting of larger fish and sharks of up to 3 meters in length.
Blue whales and Fin whales (Balaenoptera musculus and Balaenoptera physalus) Maximum accepted size: 29.9-33.26 meters, 190 metric tons; 26-27 meters, estimated 90-120 metric tons.
The blue whale is the largest animal ever known to live on Earth. There are multiple subspecies of this creature. The pygmy and North Indian subspecies are the smallest, average 21-22 meters, maxing out at 24.1 meters; the Chilean subspecies averages at 23.5 meters with a maximum for 25.6 meters; Northern Hemisphere blue whales average between 22-24 meters with a maximum of around 27 meters in the North Pacific and 28 meters in the North Atlantic. The largest is the Antarctic subspecies, where mature adults average between 24-26 meters (7,9). Males are slightly smaller than females. The largest blue whale whale scientifically measured was a 29.9-meter Antarctic female, however it is fairly accepted by members of the scientific community that the largest blue whales historically grew beyond 30 meters. This is mainly due to the consistency of whaling data and other sources. Between 1916-1949, 88 blue whales ranging from 30-33 meters have been reported in the Southern Hemisphere (1). The largest ever recorded was a female caught off of South Georgia in 1909 that measured 33.58 meters long (1). Similar to the 24-meter sperm whale, this claim has doubts as it comes from a pre-1920s whaling record, but it is relatively more accepted by authors. The claim of 33.58-meter blue whale, while huge, is relatively less ridiculous than the sperm whale claim. Otherwise, I also see 31 meters commonly listed as the maximum size for blue whales.
Update (4/12/2021) The New Bedford Whaling Museum and Dr. Nick Pyenson of Smithsonian Institution’s National Museum of Natural History support the findings from the 1928 Norwegian study. The measurements themselves where made by whaling directors, but the study describes that they were assigned specific instructions to measure the whales in the official scientific manner, so the scientific measuring technique was still used. They report a female blue whale that was 33.26-meters long and a 32.64-meter long male, both caught off South Shetland in 1926. 5 other whales over 31.38 meters (100 Norwegian feet) were measured between 1922-1925 out of 6,925 whales. Since the New Bedford Museum and Dr. Pyenson approved of these findings, including the fact the study itself describes attention to the scientific standard, I’m inclined to consider this a relatively reliable report. I will add this to the maximum length range above15
The fin whale is the second longest whale. There are about four subspecies between the North Atlantic, North Pacific, Antarctic, and the pygmy subspecies. The largest of them all are the Antarctic fin whales that average between 21-22 meters when mature and can typically exceed 24 meters. Just as in blue whales, the females are slightly larger than the males. The largest scientifically confirmed individual was a 25.9-meter female, but reports of a 27.3-meter specimen is often cited for many sources. So how much do these two animals weigh?
Well, rorquals are a bit trickier compared to sperm whales because their masses fluctuate wildly depending on the seasons. Migratory whales are primarily seasonal feeders that travel to high latitudes during the summer and feed less for the remainder of the year as they reside in lower latitudes. During the beginning of the feeding season, they are at their lean body mass and they enter their fatten condition by the end of the season. In the Southern hemisphere, blue whales are projected to gain 50% of their lean mass during the feeding season, while fin whales are projected at 30%. However, the fin whale’s weight increase was calculated from a lesser sample size. It’s suspected that the Antarctic fin whale’s seasonal weight gain is closer to a blue whale’s (7). It should be noted that the term ”fat” to described the post-feeding condition for rorquals is misleading. While increases in fat are most certainly observed, most of the weight increases occurs from muscle tissue (7). Female whales lose a lot of weight when lactating for their calves and they can enter a greater fattened condition while pregnant. Due to these effects, the predictive power of formulae are limited, as their data is often a mix of lean, fattened, and intermediate individuals.
Here, I will specifically be evaluating the Antarctic blue whale subspecies using this formula that’s unadjusted for the 6% body weight loss from flensing.
Using their mean body lengths, physically mature male Antarctic blue whales average 102 metric tons and females average 117 metric tons (7). These weights would be roughly intermediate of their two body conditions. The corresponding lean and fatten masses would be 84-125 metric tons for males and 94-140 metric tons for the females (7). The heaviest individual ever weighed was a 27.6-meter female caught on March 20, 1947 (2). One of my sources cites this female as weighing 190 short tons/ 173 metric tons (8); this is the source cited on Wikipedia and has been copied for other websites. However, two of my other sources, in addition to my field guide, suggests it was actually 190 metric tons (1,2,9). I choose to go with 190 metric tons rather than 190 short tons because Wikipedia’s source was a conservation report while my two sources were both specialized studies concerning size metrics. Therefore, it was more likely that a mistake in unit conversion came from the authors of the conservation report. Furthermore, the original paper that cited the specimen was from a 1967 Russian study. The USSR’s use of the metric system by that time made it unlikely that the original figure was written as 190 short tons. The most interesting aspect about speculating the maximum mass is that we know for a fact the largest blue whales were at least more than 2 meters longer than the heaviest weighed individual, so chances are an animal of over 200 metric tons by the end of the feeding season very likely existed within whales 28-30 meters long.
Now for fin whales, the Antarctic subspecies will be evaluated using this formula
This formula was specifically applied for ”mid season” weights during January and February, so these whales are relatively more fattened than they were in December. Using this, physically mature Antarctic fin whales of 21-22.2 meters average 60-70 metric tons (6). The heaviest fin whale weighed piecemeal was a 22.7-meter female that weighed 69.54 metric tons, meaning its intact weight was 74 metric tons (2). Using the formula above, the 25.9-meter individual is estimated to have been 108 metric tons and a 27.3-meter specimen could have weighed 125 metric tons. Given how these lengths correspond to the average range for a mature Antarctic blue whale, this sounds about right. These animals share similar tissue compositions, so it makes sense that we’re seeing overlap between weights at equal lengths (2). Granted, this is mainly due to the seasonal variability within both species. At equal lengths, a lean or fattened blue whale will outweigh a fin whale in the same condition. I feel relatively confident about these estimates as my field guide list 120 metric tons as representing a maximum-size individual of 27 meters (9). At the bare minimum, the largest fin whales at least exceeded 90 metric tons according to another formula(2).
What allowed these two species to evolve to such sizes is their very efficient means of lunge-feeding. Despite each dive expending a lot of energy as they experience the drag force of taking in their own weight in water, they very efficiently meet their caloric demands (10,11). While this method grants them far more energy than they expend, it limits them to high-density prey distributions (9).
Gray and Humpback whales (Eschrichtius robustus and Megaptera novaangliae) : Maximum size- 15.6 meters, estimated 45 metric tons; 16 meters, 60 metric tons.
The gray whale and humpback are both whales well known for their particularly long migrations while also being among the earliest target species for commercial hunts. Mature gray whales average 12.6 and 13.1 meters for males and females respectively (12). They achieve a maximum length of approximately 15.6 meters (9). Humpback whales are of a similar size, with males averaging 13 meters and females at 14 meters (13). They are typically reported reaching an upwards of 16 meters, with at least one account of up to 18.6 meters (9). Being migratory whales, their weight is also observed to fluctuate by the season. The gray whale’s seasonal weight gain is thought to range from 12-41% of the their lean body mass while humpbacks are estimated to approach a doubling of weight (7). A humpback whale is heavier by length than most rorquals, just like the sperm whale (2). Their weight estimates will be using these formulae:
Gray whale BW=0.0051(TL)3.28 (2)
Humpback BW=0.0158(TL)2.95 (2)
The mass of the average adult gray whale is 22-25 metric tons with the maximum being 44 metric tons. By comparison, the heaviest specimen weighed piecemeal was a 13.6 meter-female that was approximately 36 metric tons after adjusting (2). For the humpback, the average individuals ranged from 32-40 metric tons. A 16-meter humpback would have been approximately 60 metric tons and a 18.6-meter specimen would weigh 93 metric tons. The largest piecemeal weight was 43 metric tons for a 13.8-meter female (2). I would avoid citing the 18.6-meter individual as there’s relatively little substantiating humpbacks reaching such sizes. The 16-meter estimate seems much more realistic.
Overall, these results are very consistent to what I’ve seen reported by most sources, including my field guide (9). Gray whales primarily suck and filter food from the bottom of sea beds and may occasionally partake in skim or gulp-feeding. Humpbacks employ a larger diversity of feeding techniques ranging from lung-feeding and use of bubble nets to trap small fish (9).
North Pacific Right Whales and Bowhead whales (Eubalaena japonica and Balaena mysticetus): Maximum size- ~20 meters for both species; 114 metric tons and 120-164 metric tons.
On a mass per length basis, these two species surpass all others. Right whales and the bowhead whale are the stockiest whales ever known. Both are members of the Balaenidae family, with the North Pacific right whale being the largest of the three species within its genus. Both inhabit cold high-latitude waters in the Northern hemisphere, though bowheads are true arctic residents who don’t migrate southward. Bowhead whales and North Pacific Right whales are basically the same size with most mature adults ranging from 15-17 meters in length and 60-80 metric tons in weight (9). As for their maximum lengths, right whales as large as 19.8 meters have been reported, with some sightings of individuals surpassing 20 meters (14). The longest measured bowhead whales approach 18 meters, but reports of some whales beyond 20 meters are also reported from 19th-century sightings and contemporary accounts by Inuit hunters (4). There’s little rejection among experts that bowheads could exceed 20 meters due to their similarity to the right whale and the lack of a robust dataset to compare against, like we do for sperm whales or blue whales. Whaling records for bowhead whales are predominantly oil yields.
Despite formulae existing for both species, I’m not going to go in-depth with the relationship for evaluating the body length-mass relationship. I have emphasized it for the other species because those cases had more extensive data regarding their average and maximum lengths. Here, the details on the longest confirmed individuals are more ambiguous, especially in the case of the bowhead whale. I will instead focus on direct measurements for the North Pacific right whale and sizes derived from oil yields for the bowhead. I will say, however, that the size curves for both species’ regression formulae were quite similar (2,4).
The largest North Pacific Right whale ever weighed was a 107 metric ton individual of 17.4 meters, that would have weighed 114 metric tons when adjusted. (2). This is the first time we have a direct measurement telling us of a non-blue whale weighing over 100 metric tons. Chances are that longer right whales would typically weigh around this mass or greater.
In order to infer the masses of historically caught bowhead whales, we need to convert the individual’s oil yield to calculated their blubber weight. Oil volumes from bowhead whales were measured in barrels (31.5 US gallons), and 193.4 kilograms of blubber was necessary to yield a barrel(4). The blubber composes about 44% of a bowhead whale’s mass, essentially the same as in the North Pacific right whale (4,2). Therefore, about 228 barrels of oil would be the expected amount from a bowhead whale that weighed 100 metric tons. Records of bowheads providing 250 or more barrels are well documented (4). There’s even one case of an individual providing 375 barrels, that would equate to a 164-metric ton animal (4)! Assuming that particular volume was accurately measured, this record provides physical evidence supporting the existence of the 20+ meter individuals reported by both explorers and Inuit witnesses. Given the general reliability of the oil yield records in addition to the North Pacific right whale serving as a strong proxy for making morphometric inferences, there’s very little room to doubt the largest bowheads surpassed 100 metric tons.
These two species evolved to such astonishing sizes because they spend much of their time in cold and rich waters where they skim-feed at the surface into huge clouds of prey using their large mouths(9). The relatively lower cost compared to lunge-feeding provided balaenids with an advantage in achieving their sizes.
You may have noticed how I brought attention to the role of the whales’ feeding strategies in acquiring their large sizes. I have done this to address a misconception that had caused some to become unenthusiastic of a whale’s size: the water was what enabled them to grow so large. What people tend to overlook is that while buoyancy may provide an advantage in supporting their weight, there are other factors involved in limiting the evolution of gigantism. The crucial disadvantage of marine environments is the lack of an efficient dietary niche that is as viable as the terrestrial herbivore’s.
The largest terrestrial animals such as sauropods that approached 80 metric tons and large Cenozoic mammals potentially achieving 20 metric tons were all strict herbivores. Plants were both abundant and imposed little cost to consume, making them the ideal food source for meeting the energy requirements for large creatures, say 15 tons or greater. Plant biomass in the ocean is very low, requiring most animals to be a predator of some sort. This is evident as cetaceans evolved from plant-eating artiodactyls to becoming carnivores as they adapted to aquatic life.
A carnivorous niche appears to heavily neutralize the advantages that buoyancy provides in attaining large sizes when compared to terrestrial herbivores. This is evident by the lack of marine taxa outside of whales that can be confidently interpreted as surpassing the largest sauropods in mass. Even the largest non-whale filter-feeders such as the Leedsichthys and whale sharks are not conservatively expected to reach 60 tons. Even baleen whales, who have been fully aquatic for 40 million years and had baleen for 25 million, averaged between 5-8 meters, with the largest species being 13 meters during most of the Miocene. Widespread gigantism did not evolve in the ancestors of modern whales until about 4 million years ago, coinciding with ecological shifts of the ocean. Macropredators such as Megalodon and Livyatan were only so large because of the unusual circumstances that was maintained by a fragile ecological balance. Once small baleen whales became extinct and replaced by larger, migratory whales, the macropredators died off. This is all evident of how the energy requirements, in addition to the eventual diminishing of a creature’s speed and agility, makes large bodies very unfit for marine animals that need to hunt their prey.
With all of this in consideration, the idea that the largest animals known to exist were actually marine carnivores rather than a terrestrial herbivore should undermine expectations. Whales’ large sizes coincided with their ecological roles, and that will be the topic for my next article.
I hope everyone reading found this article interesting and informative. If anyone has any objections towards my methodology or assessment of the data present by my sources, please get in touch so we can discuss it. And apologies for interchangeably using ”weight” and ”mass” throughout the article. I know these are different terms, but in this context they serve the same practical meaning. I learned a lot while preparing for this article, so I’m eager to learn more.
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