Whales vs Dolphins

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I mentioned in Orcas: Part 1 that the alternative name for Orca, Killer Whale, is a misnomer (an inaccurate name) because Orcas are in fact part of the dolphin family instead of the whale family. So, what is the difference between dolphins and whales?

Cetaceans

Dolphins and whales share many things in common, both belonging to a group of animals called Cetaceans. Cetaceans are aquatic, water dwelling, mammals. As mammals they are both endothermic animals that breathe air, produce milk, give live birth, and have hair. We humans also share these traits with them. As endothermic animals, they (and we) produce their own body heat and need to find ways to not lose that body heat. Most marine mammals, mammals that live in the ocean, retain their body heat through thick skin and modified fat called blubber. It is kind of like they are wearing a really thick wetsuit. Most adult Cetaceans has little to no hair so they can be more hydrodynamic, meaning they can swim easier through the water. All mammals breathe air, so cetaceans all need to surface in order to breathe but many are well adapted to holding their breath for a long time. Most dolphins have breath holding times of around 10 minutes but the deep diving Sperm Whale can be underwater for up to 90 minutes.

Odontocytes vs Mysticetes

Odontocetes (oh-don-tuh-seets) and Mysticetes (mis-tuh-seets) are groups of Cetaceans. Odontocetes are “toothed whales” including dolphins, porpoises, Orcas, Sperm Whales, Beluga Whales, etc. I know what you are thinking: “If Orcas and dolphins are “toothed whales,” how is an Orca not a whale?” Perhaps it is more correct to say: “Not only are Orcas toothed whales, they are also members of the dolphin family.” They share a more recent common ancestor with other dolphins than they do with Humpback Whales. The “toothed whale” distinction is important because other whales, the Mysticetes, have baleen instead of teeth. These whales include Humpback whales, Grey Whales, the largest mammal: the Blue Whale, and more. Baleen is made of the same thing our fingernails are made of, keratin. It is smooth on the outside and bristly, like a broom, on the inside of a whale's mouth. Plates of baleen line the roof of Mysticetes’ mouths and are used to catch small marine animals like zooplankton, krill, shrimp and small fish. The largest animal in the world eats some of the smallest animals in the ocean!

Overall, baleen whales tend to be larger than toothed whales. Because of their different ways of feeding (teeth vs baleen), they have different diets. Though their overall body structure is similar so they can be hydrodynamic, there are a few differences. All toothed whales have a fatty cavity in their head called a “melon” for transmitting sounds used in echolocation. Though baleen whales do use echolocation, they do not have this feature. Additionally, toothed whales are typically faster swimmers than baleen whales. The toothed whales also generally spend less time underwater between breaths. (The exception to that is the Sperm Whale, a toothed whale that spends over an hour under water and generally swims slower than baleen whales.) These traits are linked to the fact that toothed whales have one blowhole, the opening where they breathe, and baleen whales have two. Toothed whales take smaller and more frequent breaths where baleen whales take larger, less frequent breathes. Lastly, many toothed whales tend to be more social and travel in larger groups than baleen whales.

In summary, while dolphins are technically whales (Cetaceans) belonging to the toothed whale category (Odontocetes), there are some large differences that separate them from the baleen whales (Mysticetes).

One last wild fact: all Cetaceans belong to the Order Artiodactyla. This order also includes goats, sheep, llamas, and deer. This means whales and dolphins are distantly related to many animals we have at camp!