Collectively, both whales and dolphins, as well as their porpoise cousins, are known as cetaceans. The cetacean order comprises two subgroups: baleen whales (including gray whales, right whales, blue whales, etc.) and toothed whales (dolphins, porpoises, sperm whales, beluga whales, etc.). As members of the latter, orcas are more closely related to dolphins than they are to blue whales and the other species in the first group.
Are killer whales true whales, or are they members of the Dephinidae, or dolphin family? The answer is both, as we will explain below.
The question came to light in July 2022 after a video of a killer whale and dolphin was shared to the Reddit thread natureisfuckinglit. The first comment on the video read, “Fun Fact: Killer whales, or orcas, are not true whale, they are a species of dolphin.”
That statement is partially true. Collectively, both whales and dolphins, as well as their porpoise cousins, are known as cetaceans. The cetacean order comprises two subgroups: baleen whales (including gray whales, right whales, blue whales, etc.) and toothed whales (dolphins, porpoises, sperm whales, beluga whales, etc.). As members of the latter, orcas, Orcinus orca, are more closely related to dolphins than they are to the whales in the first group.
“In fact, they are the largest member of the Delphinidae, or dolphin family. Members of this family include all dolphin species, as well as other larger species such as long-finned pilot whales and false killer whales, whose common names also contain ‘whale’ instead of ‘dolphin,’” wrote the NOAA Fisheries in a blog post.
Baleen whales, as their name suggests, have baleen plates used to filter food like plankton and small fish. Toothed whales, also known as odontocetes, include all species of dolphin and porpoise — including killer whales — and have teeth for larger prey, including fish and other marine mammals.
"The main differences with porpoises are that they are usually smaller than other toothed whales, and instead of cone-shaped teeth they have flat, spade-shaped teeth,” wrote WDC.
“As a general rule of thumb, baleen whales are larger and slower (except the fin whale which is known as the 'greyhound of the sea') than toothed whales. Additionally, all baleen whales have two blowholes, whereas toothed whales only have one.”
As legend holds, sailors who saw orcas preying on other whales gave them the nickname “whale killer” — a name that eventually morphed into “killer whale,” notes the Ocean Conservancy.
Growing to upwards of 30 feet long, orcas are the largest of all dolphin species. Their large size may also explain why the black-and-while marine mammals often get confused for whales.
“While orcas are members of the marine dolphin family Delphinidae, their overall size is what sets them apart from others in their suborder. Today, if a dolphin reaches a size of more than 30 feet long, it may be referred to by some as a whale, but the rules of taxonomy still classify the orca as a dolphin,” wrote the Ocean Conservancy.
Aside from teeth, size and blowholes, the Canadian Wildlife Federation adds that there are several other biological factors to consider when determining whether an animal is a dolphin or a whale. Those include dorsal fins, neck vertebrae, the size of brains, social behaviors, communication methodologies, and social group structure.
Snopes spoke with Katie Doyle, an outdoor educator with a background in marine biology, who told us that “whale” is a colloquial catch-all for cetaceans.
Cetaceans include dolphins, whales, and porpoises. Within the Cetacea order, there are two suborders: odontocetes (toothed whales) and mysticeti (baleen whales). Odontocetes include porpoises, dolphins — and killer whales — as well as other toothed whales like sperm and pilot whales.
Don't even get us started on the narwhal.
Killer whales are charismatic creatures, and they often find themselves in the center of digital rumors. Here are some of Snopes’ other favorite orca stories:
- Did a Killer Whale Snatch a Beachgoer?
- Was an All-White Orca Recently Spotted Off The Russian Coast?
- Did an Orca Eat an Ice Fisherman on Camera?
- Is this a Kayaker Paddling Through a Pod of Orca Whales?
- Was a Japanese Whaling Crew Eating Alive by Killer Whales?
“Facts about Orcas (Killer Whales).” Whale & Dolphin Conservation USA, https://us.whales.org/whales-dolphins/facts-about-orcas/. Accessed 4 Aug. 2022.
Fisheries, NOAA. “11 Cool Facts About Whales, Dolphins, and Porpoises | NOAA Fisheries.” NOAA, 26 May 2022, https://www.fisheries.noaa.gov/feature-story/11-cool-facts-about-whales-dolphins-and-porpoises.
"11 Cool Facts About Whales, Dolphins, and Porpoises | NOAA Fisheries.” NOAA, 26 May 2022, https://www.fisheries.noaa.gov/feature-story/11-cool-facts-about-whales-dolphins-and-porpoises.
“How to Tell the Difference Between Dolphins and Porpoises.” Ocean Conservancy, 22 Feb. 2019, https://oceanconservancy.org/blog/2019/02/22/tell-difference-dolphins-porpoises/.
ITIS - Report: Delphinidae. https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=180415#null. Accessed 4 Aug. 2022.
kilroy000. “Fun Fact: Killer Wha….” R/NatureIsFuckingLit, 27 June 2022, www.reddit.com/r/NatureIsFuckingLit/comments/vm1w0w/killer_whale_and_dolphin_spotted/idyiut0/.
What Is the Difference Between Whales, Dolphins and Porpoises? – Your Connection to Wildlife. https://blog.cwf-fcf.org/index.php/en/what-is-the-difference-between-whales-dolphins-and-porpoises/. Accessed 4 Aug. 2022.
“Why Is an Orca Not a Whale?” Ocean Conservancy, 13 Mar. 2019, https://oceanconservancy.org/blog/2019/03/13/orca-not-whale/.