Sunday, July 12, 2020

Whale, Dolphin, or Porpoise? A meaningful question about meaningless terms

Disclaimer 1: I’ve made no attempt to dive into any literature regarding the definition of any of these terms; this is instead a “gestalt” approach calling on my admittedly shallow experience in whale paleontology and successful and (especially) unsuccessful attempts to communicate my science to the public. To be honest, I don’t know if some essay exists about the common names of marine mammals with recommendations, and I don’t care: if it exists, it’s hardly done its job, has it? Nevertheless, I’d like to hear about it.

Disclaimer 2: The common names I use are all from the List of Marine Mammal Species and Subspecies published by the Society for Marine Mammalogy; these common names are generally not debated, though SMM writes: “common names are arbitrary and change with time and place.” Nevertheless, common names for individual species seem to be quite stable and meaningful to some degree; it is the bigger labels – and common names of higher taxa – being dissected here. You can view the list here. 

Cetaceans that stretch the definitions of names (top) and those that don't (bottom). Top left: the Risso's dolphin, despite being quite large and lacking a beak; Top right, a Sowerby's beaked whale, a whale despite having a beak. Bottom left: a spinner dolphin; bottom right: humpback whales. Photo credit:; Pierre Jaquet via Flickr;; Tony Wu, NPL.

Whale, Dolphin, Porpoise: what do these words mean? 

I’d rather be talking about our new study on the large extinct killer dolphin Ankylorhiza tiedemani, but after speaking with several journalists about it I’m instead motivated to have a brief rant discussion of the vernacular taxonomy of cetaceans. I get asked (or see) these sorts of questions/statements frequently:

            “So is it a whale or is it a dolphin?”

            “That’s a whale tooth, not a dolphin tooth”

            “The killer whale is actually a dolphin”.

These words are used with such imagined precision and it breaks my little heart every time because, well, they don’t mean a whole lot. So many arguments are had over the identification of cetacean fossils, for example, when in fact different completely defensible alternative definitions exist and so many are comparing apples and oranges. And, I’ll note right now: I’ve never heard an academic in mammalogy or paleontology ever get hung up on what the definition of these mean, because we all A) tacitly acknowledge that they’re not very well-defined and a bit meaningless in practice and B) use scientific terms that have extremely precise meanings. So, a quick break down of the terms.

Whale – from the Old English hwael, Old Norse hvalr, Dutch & German wal, etc.
Definition according to Merriam Webster Dictionary:any of various very large, aquatic, marine mammals (order Cetacea) that have a torpedo-shaped body with a thick layer of blubber, paddle-shaped forelimbs but no hind limbs, a horizontally flattened tail, and nostrils that open externally at the top of the head”

Dolphin – from the Greek delphin, Latin delphinus, old French dauphin.
Definition according to Merriam Webster Dictionary: “A) any of various small marine toothed whales (family Delphinidae) with the snout more or less elongated into a beak* and the neck vertebrae partially fused. B) any of several related chiefly freshwater toothed whales (as of the families Platanistidae and Iniidae)”

*beak, of course, is the cetological term for the snout in a cetacean that protrudes beyond the melon – think of the bottlenose in a bottlenose dolphin.

Porpoise – from the old French porpais, translating to “pig fish” – originally from Latin porcus + piscus, porc + peis in French.
Definition according to Merriam Webster Dictionary: “a blunt-snouted usually dark gray whale (Phocoena phocoena) of the North Atlantic and North Pacific that typically ranges from 5 to 6 feet (1.5 to 1.8 meters) in length.”

The definition of “whale” above perhaps is the most broad, and characterizes dolphins and porpoises as well. The definition of “dolphin” at first seems to only include the Delphinidae, but then admits that there are some other dolphins – mostly riverine – that are similar-ish in external body form that can be called dolphins. The definition of porpoise offered by Merriam Webster highlights one species, the harbor porpoise. Dolphins v. porpoises seems rather clear here: dolphins have beaks, and porpoises do not. It is from these definitions that many accept a quasi-taxonomic use of the words: dolphin means “Delphinidae” and porpoise means “Phocoenidae” – the families containing the bottlenose dolphin and harbor porpoise (respectively).

What about other definitions? I’ve read elsewhere that a whale could be defined as any cetacean lacking a beak but being larger than 9 feet in length, and that porpoises are any cetacean lacking a beak smaller than that, and in many variants, possessing a triangular rather than hooked (falcate) dorsal fin. This at first seems fine: phocoenids mostly have triangular dorsal fins and none that live today possess a beak, clearly differentiating them from delphinid species like the bottlenose dolphin. However… what about the genus Cephalorhynchus? These are a fascinating group of southern hemisphere delphinids with a “ring species” biogeographic pattern of dispersal around the southern ocean – and none have a beak or a falcate dorsal fin. Externally, they are so similar that if a stranded individual were so decomposed that the teeth had fallen out and identification was not possible based on the coloration, you would probably need to remove the skull in order to tell which family it belonged to. On top of this, there has been rampant use in the past of the word porpoise for delphinids with beaks (spinner porpoise, bottlenose porpoise, etc.), as recently as the 1970s – in peer reviewed papers by marine mammalogists like William Perrin!*

*I have also read this may be specific to Hawaii, where local fisherman call all small cetaceans porpoises because they instead use the term “dolphin” exclusively for the dolphinfish, which really chaps my ass because there’s already a &#$ing local indigenous name for that species – Mahi-mahi, that is now used more frequently than dolphinfish outside of Hawaii.

Phylogenetic distribution of common names for cetaceans. Phylogeny from McGowen et al., 2011. Only the term porpoise, and only in its modern usage, appears to define an actual clade.

The distinction between “dolphin” and “porpoise” is sadly, in my view, the clearest, and matters only become worse when you take a closer look at “whale”. The first and biggest problem is that whale doesn’t even attempt to mean anything biological: it includes both baleen whales and large odontocetes, which, granted, are all cetaceans, but some whales (large odontocetes) are obviously much, much more closely related to whatever dolphins and porpoise are than others (e.g. mysticetes). There are two aspects to the difference between whales and dolphins I’ve seen in most definitions or uses of the words: 1) whales lack a beak and 2) whales are larger than dolphins. At first glance, this works: baleen whales are all larger than dolphins, and sperm whales, and killer whales are as well – and none of these have a beak. But, there are, as before, exceptions.

The first exception are the beaked whales: family Ziphiidae, all of which are larger than dolphins but… paradoxically have beaks. One is even called the bottlenose whale! Another, Berardius, is the second largest odontocete after the sperm whale Physeter, measuring in at 11 meters or more – larger than minke whales, but smaller than the largest bryde’s whales. Berardius, for the record, most certainly has a beak.*

*I was lucky enough to participate in a necropsy of a stranded female B. arnuxii on a frigid, foggy beach on the southern tip of the south island of NZ during my Ph.D.

The second exception are some of the smaller species of the “blackfish” – the Globicephalinae. These are a highly derived group of darkly pigmented blunt-snouted delphinids with some suction feeding adaptations. Despite being large bodied, darkly pigmented, and lacking a beak, the killer whale is not actually a member of the Globicephalinae, and is instead allied with a number of robust Tursiops-like fossils in the Orcininae, the earliest diverging lineage within extant Delphinidae. Three of these are the same size as most dolphins – 6-10 feet in length (2-3 meters) – these are the melon-headed whale Peponocephala electra, pygmy killer whale, Feresa attenuata, and the snubfin dolphins, Orcaella spp. (Irrawaddy river dolphin, Australian snubfin dolphin). Peponocephala (8-9 feet, 2.6-3 meters) and Feresa (6-7 feet, 2-2.3 meters) illustrate that not all “whales” are large-bodied. Orcaella, the snubfin dolphins, are small (6-9 feet, 2-3 meters), and called dolphins yet lack a beak! If your brain wasn’t already close enough to melting out through your ears, let us also consider the relatively large delphinid Grampus griseus – the Risso’s Dolphin – which is a large globicephaline, smaller than a pilot whale or the false killer whale, but much larger than the rest of the globicephalines. It is large, and lacks a beak – externally it looks the same as a pilot whale aside from coloration.

These terms are old with origins in the whaling industry, pre-dating modern biology.

Whale also is frequently used as an umbrella term to refer to cetaceans in general, thereby tacitly including dolphins and porpoises rather than always being distinguished from them. The term “toothed whales” is the broadly accepted vernacular name for the Odontoceti, and likewise, “baleen whales” for the Mysticeti. In older literature (prior to World War II) you will find frequent references to the amusingly named “whalebone whales”, and after cursory reading, you realize (just quickly enough to avert a brain aneurysm, in my case) that all whalebone whales are baleen whales. As it turns out, “whalebone” is an old whaling term for baleen, which would be cut into strips and sold on shore to be used for the boning in ladies’ corsets.

Another term you may hear is the “Great whales” – which is defined by the International Whaling commission as the most economically viable whales for the purposes of whaling – most baleen whales (except for Eden’s and Omura’s whales), and the sperm whale. This is obviously not a taxonomically informative moniker.

In summary, just looking at the distribution of modern cetacean common names indicates that “whale”, “dolphin”, and “porpoise” have no consistently used, biologically meaningful definitions. They are informal terms, with multiple accepted definitions.

Testing the water: an informal twitter poll

I started writing this post, and then realized as an afterthought, that I should post a poll on twitter asking folks to vote on what they think a particular cetacean was – the intention was to ask my twitter followers “should the common name of this species have whale, dolphin, or porpoise in it?” not “is this a cetacean?” whereby whale would have been correct every time. So, who knows how useful the results are – regardless, I used the exact imprecise language I’m railing against in the rest of this post, so confused results do speak for themselves. It’s also worth noting that at present I have perhaps 5,000 followers give or take, and while many are scientists, most are not, and even many scientists are not guaranteed to be familiar with obscure cetacean species I’ve intentionally chosen to prove a point. [Admittedly, I have jumped the gun an hour or so, as the polls are not yet finished, but I don't expect them to change much. If there is any change I will update them accordingly].

The first poll had an unlabeled photograph of a dolphin-like animal leaping from the water – without scale. Most respondents (~49%) called this a dolphin (with the remaining votes split (25% each) between porpoise and whale) – but it is not a dolphin. This is a female Sowerby’s beaked whale (Mesoplodon bidens) – difficult to tell, but the pectoral fins are pretty far from the head. Answer: WHALE. [photo credit:]

The second poll has a similar looking animal leaping out of the water – and most (70%) responded correctly. This is a spinner dolphin (Stenella longirostris) known for its acrobatic spinning breaches. This was formerly frequently called the spinner porpoise, so you get a free pass if you wrote porpoise. Answer: DOLPHIN. (or porpoise?) [photo credit: Getty Images TV via youtube]

The third poll is just a cute little face poking out of the water – a face that is dark and lacks a beak. This one was clearly confusing, as only a slight majority – 41% - identified it as a porpoise, and about 30% said whale or dolphin. This is not a porpoise, however – it is a Heaviside’s dolphin (Cephalorhynchus heavisidii), one of the smallest dolphins, and a beakless one at that – in the porpoise-mimic genus Cephalorhynchus. Answer: DOLPHIN. [photo credit: S. Elwen, Namibian Dolphin Project]

The fourth poll shows a sadly dead, strikingly countershaded animal with an absurdly large dorsal fin, a white eye ring, and black lipstick. Most respondents (~70%) correctly said this was a porpoise. This is indeed the spectacled porpoise, Phocoena dioptrica. That’s actually my Ph.D. adviser R.E. Fordyce (U. Otago, Geology dept.) on the left*, and Steve Dawson (U. Otago, Marine Sciences dept.). Like the Heaviside’s dolphin above, it does not have much of a beak. Answer: PORPOISE. [photo credit: 1 News, NZ]

*This beautiful porpoise stranded on the Otago Peninsula while I was in the Fordyce lab - but it was September 2014 and I was in the throes of Ph.D. writing, and desperately attempting to complete my Ph.D. thesis before January 10, my arbitrarily set deadline (which I made). I naturally had to decline the invitation, as necropsies followed by detailed dissections (this is R.E. Fordyce we're talking about; detail is everything) eat up several consecutive days.

The fifth poll, just for fun, was my illustration of the recently re-named Ankylorhiza tiedemani – which I call a ‘killer dolphin’ or ‘giant dolphin’. Respondents were pretty split between calling this a whale (~43%) or a dolphin (~45%), with a few for porpoise. Answer: ???

What’s the moral of the story from these polls? These terms are helpful in some cases but otherwise prove my point that they do not reflect biological groups. Reliance upon these terms can lead to confusion.

Is the Eocene archaeocete Ambulocetus a whale, dolphin, or porpoise? Artwork by Carl Buell. 

Fossil whales, dolphins, and porpoises – a whaleontologist’s perspective

Paleontologists have a very laissez faire approach, because we are constantly befuddled by strange cetaceans that further blur the (admittedly very crookedly drawin) lines between these terms. Are four legged Eocene semiaquatic archaeocetes - like Pakicetus - whales, dolphins, or porpoises? They look rather close to a dog to be called any (but are typically referred to as whales). What about some early sperm whales that had relatively long rostra and may have had a beak, like the Miocene Zygophyseter? If we stick to the strict Dolphin= Delphinidae, and Porpoise = Phocoenidae taxonomy – what about dolphin-like phocoenids with beaks (e.g. Piscolithax), or extinct delphinoids, like Kentriodon, that are not delphinids, but also small-bodied with a beak? What about large kentriodontids the size of pilot whales, also with a beak? What about our newly named Ankylorhiza – is it a whale or a dolphin?

A somewhat outdated but nicely illustrated tree of modern and extinct cetaceans, highlighting the number of wholly extinct groups discussed by paleontologists without incident; modified from Barnes et al. (1985: Marine Mammal Science).

The strict dolphin v. porpoise dichotomy is perhaps somewhat useful for modern cetaceans (delphinids including porpoise-like species, and others labeled as whales, notwithstanding), but completely falls apart thanks to a slew of extinct dolphin-like species that are not delphinids. This is not universal, but from 15 years in the field, I can say that whaleontologists do the following things: 1) whale broadly is used by us to mean cetaceans, and all archaeocetes are generally referred to as “whales”. 2) Dolphin is broadly used for any small odontocete, including those with short rostra (e.g. some fossil globicephalines, the extinct xenorophid Inermorostrum), but also for larger species with beaks. Large dolphins, like Ankylorhiza or the Miocene Hadrodelphis, are simply called large dolphins or giant dolphins. Squalodon is called a shark toothed dolphin by most. In general, with the exception of some modern species, we generally use the term dolphin to indicate any extinct odontocete that is not a sperm whale or a beaked whale. 3) Porpoise is always meant to refer to the family Phocoenidae. 4) River dolphin may be convenient for modern species, but most extinct relatives of the four modern genera – Pontoporia, Inia, Lipotes, and Platanista – were fully marine. River dolphins are three or four separate clades representing a minimum of four riverine invasions.

One thing that seems obvious from my look back is that the terms dolphin and whale are frequently used for many extinct clades – but always with a family name in tow: e.g. eomysticetid whales; kentriodontid dolphins, etc.

Coronodon havensteini, a baleen whale with teeth - a common source of confusion in our museum. Photo by me.

Toothed whales, or Echolocating whales

Now that we’ve clarified paleontological usage of whale, dolphin, and porpoise, it’s time to take a closer look at the two major groups, and terms that at first glance *appear* to be fine. Odontocetes are the toothed whales, and Mysticetes are the baleen whales. But, these vernacular names become problematic and confusing when communicating about fossils to a lay audience. Some modern odontocetes don’t have any erupted teeth or only have some tusks (e.g. narwhal, most beaked whales, risso’s dolphin), and many extinct odontocetes similary had only tusks or were completely toothless (Inermorostrum, Odobenocetops, Australodelphis, Vanbreenia, Dolgopolis). This is not too much of a problem, to be honest.

Instead, the real problem is the toothed mysticetes – baleen whales with teeth. Toothed baleen whales are the earliest lineages of mysticetes that still had teeth – like Coronodon from South Carolina, the Aetiocetidae (north Pacific flat-snouted teeth + baleen bearing mysticetes), the Mammalodontidae (big-eyed Australasian toothed mysticetes), and the Llanocetidae (southern hemisphere large bodied toothed mysticetes with large gaps between teeth). We recently had a comment on a social media post about Coronodon exclaiming “baleen whales don’t have teeth!”

While I have no idea how to rebrand “baleen whales”, I have found a bit of a helpful compromise in the past few years: rather than used the far more problematic term “toothed whales”, which relies upon modern species and rapidly falls apart after cursory consideration of fossils, I’ve started calling odontocetes “echolocating whales” since discoveries like Cotylocara macei suggest the origin of echolocation to be very, very early within the Odontoceti, quite possibly at the base of the clade itself. A major exception to this is a paper that Dr. Rachel Racicot published (I was a coauthor) on an Olympicetus-like dolphin from the Oligocene of Washington state that apparently could not echolocate, thereby implying that echolocation evolved twice within Odontoceti – or that this dolphin lost the ability to echolocate. This probably doesn’t matter much, to be honest, when you consider that virtually all modern and extinct odontocetes have structures otherwise indicative of some facial structures associated with sound production – and that it’s possible that our Olympicetus-like dolphin may have lost the ability to echolocate. Such a case is clear with Odobenocetops, which either had a tiny melon (O. leptodon) or probably did not have one at all (O. peruvianus). To clarify: there are far fewer odontocetes that cannot/could not echolocate than there are whales with teeth that are not odontocetes. Therefore, I think the term “echolocating whales” is probably a better common name than “toothed whales”. 

So, what the hell is an orca? A whale or a dolphin?

Now we’ve come full circle. Is an orca a killer whale, or a killer dolphin? It’s both, really. Because it’s a member of the family Delphinidae, it’s totally cool to call it a dolphin. If found as a fossil, whaleontologists probably would’ve just called it a giant dolphin. At the same time, whale doesn’t really have a specific biological meaning, so it’s also just as fine to call it a whale. If you’re going to raise the point, you may as well indicate that the Delphinidae are an ecomorphologically disparate clade of cetaceans including dolphins, some that look and behave exactly like true porpoises, and some that are called whales. So, don’t argue with people because when you get down in the weeds about dolphin v. whale, none of it makes any goddamn sense.

A possible compromise? A whaleontologist’s glossary of vernacular terms

The semiformal vernacular nomenclature used by paleocetologists suggests that a slightly more precise way of talking about cetaceans is easy and can substantially clarify communication with the public. Here is a brief synonymy list of terms I’ve heard used in paleocetology and marine mammalogy (or used personally without precedent). It avoids for the sake of useless repetition names including the family (e.g. xenorophid dolphins). If you have more suggestions, please let me know in the comments and I'll consider adding them.

Whale = any cetacean, archaeocete or neocete alike
Ancient whales**** = archaeocetes
Baleen whales = Mysticeti
Toothed baleen whales** = toothed Mysticeti
True baleen whales or baleen-bearing whales** = Chaeomysticeti
Right whales = Balaenidae
Rorquals* = Balaenopteridae
Gray whales = Eschrichtiidae
Pygmy right whales = Neobalaenidae
Toothed whales or echolocating whales = Odontoceti
Dolphin**** = 1) for extant taxa: any odontocete without whale or porpoise in the common name; 2) for extinct taxa: any odontocete that’s not a phocoenid, physeteroid, ziphiid, or globicephaline
Shark-toothed dolphins**** = “Squalodontidae”
Spear-toothed dolphins*** = Waipatiidae
Swordfish dolphins*** = Eurhinodelphinidae
Porpoises = Phocoenidae
Oceanic dolphin = Delphinidae
Blackfish**** = Globicephalinae + killer whales
River dolphin**** = Platanista, Lipotes, Inia, Pontoporia & extinct allies (marine or otherwise)
White whales = Monodontidae
Sperm whales = Physeteroidea
Walrus faced whales = Odobenocetops

*names used by mammalogists but are probably useless for science communication
**extinct subdivisions/subtaxa of these could benefit from better common names, thus far the family name is used exclusively
***names I use that may or may not ever catch on
****names that in no way refer to monophyletic groups