Fin Whale — World’s Second-Largest Animal


Updated on 09/20/2022

Finner, razorback, flathead, common rorqual, herring whale, finback whale — these are all names for the fin whale, an animal that few outside of the marine biology or maritime communities know or care about. But it is a majestic animal with sleek hydrodynamic lines and curves that roams the world’s oceans gulping down plankton and fish in astonishing quantities. Second in size only to its slightly longer but much heavier cousin the blue whale, the fin whale (Balaenoptera physalus) is the second-biggest animal on Earth, and likely one of the top 5 biggest animals ever to exist!

Big and Fast

Even though fin whales are found in all the world’s oceans, ask anybody what a fin whale is and they would probably reply with a blank expression. Ask about a blue whale and they’d usually give at least a look of recognition because it’s the biggest and the one everybody hears about. It also helps that there’s a huge model of a blue whale hanging in the Milstein Hall of Ocean Life at the American Museum of Natural History that is seen by about 5 million visitors each year. But fin whales have nothing to be ashamed of in playing second-fiddle to the blues. An adult fin whale male can grow to over 25m in length (about 75ft), and a female can top out at 27m (about 85ft). As for mass, male fin whales grow to about 70,000kg (about 154,000lbs), while their female counterparts bump around the ocean carrying 120,000kg of blubber, baleen, bone, and muscle (about 265,000lbs). In general they are longer and leaner than most large whales. Blue whales, for comparison, are thicker around the midsection.

You’d think after looking at the numbers that fin whales are nothing more than a big, lumbering hulks floating in the ocean, but you’d be criminally wrong in your assumption. The fin whales whale is quite a fast swimmer — believed to be the fastest of all the large whale species — and has often been called “the greyhound of the sea” because of the speeds it can reach. Over the last 50 million years of whale existence, all whales became streamlined as they grew sleeker and became more efficient swimmers. Fin whales very well adapted to and streamlined for oceanic travel and can cruise along at about 20mph (35km/h) with short sprint speeds reaching 30mph (45km/h). For comparison: sharks top out at 25mph (40km/h); killer whales can reach about 32mph (51km/h); an average jet-ski maxes out around 50-60mph (80-90km/h); and sailfish can hit about 68-70mph (110km/h). Throw in the fact that the fin whale outweighs all these animals and the recreation vehicle put together, it’s a remarkable amount of force fin whales are able to generate in their swim strokes to move at those speeds.


Fin whales are for the most part easy to identify partly because they are so huge, but also because of the distinct and pronounced ridge that runs along their back all the way past their dorsal fin to the flukes, which is why they are also called “razorbacks”. They have triangular-shaped heads that are mostly flat on top, with eyes at the sides just above the jawline toward the back. They tend to be blackish gray in color on the top half of their bodies, sometimes brownish, with white bellies from chin to flukes. One rather odd bit of coloring for fin whales is in their mouth area. All fin whales have asymmetrical coloring on their lower jaws — the left half of their jaw is blackish gray, and the right half is white. What’s somewhat weird is that their tongues have the opposite coloring (right dark, left light). This may be because when they feed, the whales sometimes turn on their side and therefore want to keep intact their camouflage especially when circling a school of fish. It’s also possible that it’s simply a genetic quirk that got handed down from whale generation to whale generation. Whichever the case, there is no clear-cut reason for the asymmetrical coloring.

When whale watching, identifying a fin whale can be difficult from a distance. It is often confused with the slightly smaller sei whale, which has similar coloring. Like all whales, when they come up for air they let out a big exhale or “blow” before inhaling and diving again. This exhale, because of the water vapor in it, condenses into a visible mist and can be seen from some distance. These mist cloud patterns can be markers for the type of whale you’re viewing. That is, these blows have distinct patterns from species to species. As for the fin whale, its blow pattern is tall and shaped like a thin upside-down cone.

Whales also have distinct patterns of surfacing. A fin whale when it surfaces to breathe will first expose its head and blowholes, and then blow. It then takes in its air, and goes back underwater, first the head, then exposing its dorsal fin before disappearing beneath the waves sometimes with a little roll. A sei whale has a similar blow pattern, but instead of doing a dive like a fin whale, the sei exposes its blowhole and dorsal fin at the same time, and then just sort of sinks back beneath the waves like a soggy piece of driftwood.

Whale Food

Fin whale swimming on its side feeding. Clear in this picture is the coloring on the left side of the whale’s mouth. The other side is white. The tongue happens to have the opposite coloring — dark on the right, light on the left. (Image by NOAA)

Being a gigantic whale, it is a baleen whale as opposed to a toothed whale. All the biggest whales are baleen whales, except for the massive sperm whale, which has teeth, but it is not as big as fin whales or blues. Having baleen in place of teeth on the top jaw is like having a fine-toothed comb made out of keratin — the hair and fingernail stuff — hanging down from your gums. The baleen acts like a sieve. The way baleen whales feed is they take a big gulp of plankton-filled water into their mouths and then use their massive and powerful tongues to push the water out through their baleen, which filter out the yummy bits. This is also why baleen whales tend to have really massive and strong tongues (which by the way, are tasty bits of meat for ocean-going scavengers or predatory orcas).

Like other baleen whales, fin whales eat mostly plankton, but they also gobble up squid, herring, mackerel, and sandlance fish as well as any other fish of similar size unlucky enough to get caught in a finback’s gulp. Often times, fin whales will use their speed to swim circles around a school of fish causing them to compact into a dense bait ball — a method often associated with dolphins and other whales. The whale then turns into the ball of fish and takes a big gulp.

A Fin Whale Life

Fin whales are believed to have an 80- to 90-year lifespan, and they spend a good deal of it alone. They generally don’t roam around the oceans in huge pods with other fins, but they can be found in small groups of 2 to 7 whales. During migrations, they can be found in as part of a very temporary super group with upwards of 50 to 300 whales. More often they are observed swimming around alone. In the North Atlantic, fin whales have been found as part of a much larger interspecies group feeding alongside humpbacks, minke whales, and dolphins, possibly as part of a semi-coordinated hunt. In general fin whales don’t form long-term bonds with other whales but tend to group and ungroup as prudent.

As for sex, little is known about where they do it or how they pick mates. Despite the fin whale’s size and relative ease in finding them, marine biologists generally don’t have the resources to follow fin whales around the ocean for months on end in the off chance they’ll see a couple getting it on whale style. It is believed that their copulatory grounds are in warm waters nearer to the tropics, but nobody has actually seen them in the act. It probably looks like humpback whale sex, which you can see here (NSFW).

The gestation period for fin whales is about 11 months. Female fin whales generally give birth every 2 to 3 years to one calf in tropical and subtropical zones during winter. These calves when they pop out of their mothers have a mass of 1,800 to 2,700kg (4,000 to 6,000 lbs) and measure about 6m (18ft) in length. Young whales then nurse for the next 6 to 7 months until they get big enough (around 12m or 36ft) to follow their mothers to colder feeding grounds. Between ages 6 and 10 is where male fin whales become sexually mature, and females around ages 7 to 12. Age 25 is about the time where fin whales reach their full size and stop growing.

Fin whales have been known to mate with blue whales to produce hybrid offspring, which themselves are often fertile. It’s not a common thing, but not exactly an uncommon thing. For the most part, the differences between blues and fin whales are mostly superficial. They live similar lifestyles, roam similar waters, eat the same food, and behave in similar fashions. So in some ways, it makes more sense for them to have sex with each other than for them not to.

Two cute yet vicious orcas surfacing, orcas are the fin whale’s only natural predator. They generally prey on very young, very old, or very sick fin whales, with healthy adults being mostly left alone. True they also eat fish, and there is one particular pod known for having a taste for great white shark entrails, orcas have no qualms about drowning then eating fin and other whales. What makes them particularly nasty and sadistic is that often times they will attack other whales what seems to be a good laugh and nothing more. They’re also known for throwing baby sea lions up into the air for kicks, sometimes not even eating the sea lion carcass when they are done with the poor thing. Orcas are indeed the supreme assholes of the sea who spend their lives tooling around the ocean looking for shit to fuck up. They aren’t called “killer whales” for nothing. (Photo by Robert Pitman, NOAA)

Threats to Fin Whales

If it weren’t for humans, fin whales wouldn’t have too much to worry about in life. Since they’re so huge, other marine animals tend to leave them alone, except for orcas (killer whales), who are the fin whale’s only real predators. Orcas in general will hunt or terrorize just about any marine animal they come across. Newborn and very young fin whales who are not as big and cannot swim as fast as their parents are the most at-risk for getting eaten by orcas. Adults protect themselves by using their massive tails to bash away predators, but most of the time, they will use their speed to simply outrun orcas.

Humans have been the main enemy of pretty much all whales. Having been hunted to near extinction, fin whales are currently a protected species, but not everybody agrees to adhere to that protection, at least not entirely. Along with a few small aboriginal populations in Greenland and other small local populations (who really should be given a pass here since one whale can feed a village for weeks), whaling is still legal in Iceland, Japan, and Norway despite the fact that commercial whaling has been resoundingly rejected by all other countries. Japan is far and away the worst offender in that they actually import whale meat from the other two whaling countries, which makes it the biggest consumer of whale meat.

This chart shows the number of whales hit by boats broken down by species. Fin whales overwhelmingly are the most-hit species of whale. (Chart by NOAA)

The astonishingly ridiculous part of the whole enterprise is that these countries hunt whale in the name of “science”, which is a big steaming heap of legal-loophole bullshit. By treaty they are allowed to hunt a certain number of whales each year for “scientific research”. Apparently it’s normal in these countries for scientific research subjects to be served up for dinner with a side of vegetables and rice. Total nonsense.

As for fin whales in particular, records are somewhat unreliable as for how many are actually harvested, but in 2009, Iceland set a quota for 150 fin whales to be taken over 5 years.

Aside from whaling, the biggest dangers for large whales is getting run over by ships. The number one type of vessel that hit whales whales were navy vessels, which makes sense because they tend to travel at high speeds across the world’s oceans with little regard for what they’re running over. Navy vessels are also designed to be quieter which may also contribute to their bashing into unknowing whales. The second biggest offenders are cargo freighters that carry goods across the world’s oceans. These also travel at high speeds giving whales little or no time to react. Ironically, whale-watch boats account for the third-most whale strikes.

This chart breaks down whale strikes by the type of vessel that hit the animals. The number one cause “Navy” makes sense since warships and subs regularly rip about the ocean on maneuvers. The second-biggest cause, container/cargo/freighter also makes sense as the boats tear through shipping lanes, but the third-biggest cause, whale-watch boats, is a bit of stinging irony. (Chart by NOAA)

As for fin whales themselves, according to a U.S. National Oceanic and Atmospheric Administration study, they are by a fairly large margin the most-hit-by-ship whales in the world (second-most hit are humpbacks). The study, put together back in 2004 (, analyzed available data on ship strikes from 1978 to 2002. In all, 292 ship strikes were confirmed, which is on the low end of estimates. These were reported incidents where the boats either detected the impact (the crew felt the impact or or saw a freshly hit whale by the side of the boat), or saw the results of a hit on the boat (dents in the hull, parts of whale lodged in propellers, etc.).

Lastly, habitat destruction and pollution make the lives of fin whales and all other marine animals difficult. Plastics in the water which get into animals, lower oxygen levels due to pollution runoff, and reductions in krill populations (one of their favorite and most important foods) have kept fin whale levels rather low.

Not the most exciting but…

…fin whales are unique among baleen whales in their shape and odd asymmetric coloring. Additinaly, they are just as important to the greater ocean ecosystem as any other top-level predator, occupying the same top spot in the oceanic food chain as their slightly bigger blue whale cousins. But as it is with most of the topics covered on, fin whales do not get the love they deserve, which is a shame. Perhaps someday some enterprising science museum curator will see fit to display a life-sized fin whale model much like the gigantic blue whale model hanging from the ceiling at the American Museum of Natural History in New York, so that all would be able to bask in the splendor of this magnificent aquatic beast. Until that day, most people including even modest whale enthusiasts will continue to overlook the lovely fin whale.

To see a well-produced overview of the fin whale that covers things quite nicely, take a look here. For some nice fin whale footage that was taken from a drone flying over the ocean, have a look here.