The waters of Puget Sound, including those surrounding Vashon, are host to many species of cetaceans — the name given to the group of marine mammals that includes all the whales, dolphins and porpoises.

Our local species range from small porpoises to several of the so-called great whales. Over the next few weeks, I’ll introduce some of our local cetaceans to readers, and summarize the essentials of their biology and behavior.

First, a bit of taxonomy. In the 4th century BCE, Aristotle recognized that cetaceans breathed air, gave birth to live young, and nursed those offspring with milk; yet he still considered them to be fish. It was not until 1758 that they were correctly identified as mammals; this was the doing of the Swedish botanist Carl Linnaeus, who created the classification system for all living things that remains in use today.

Cetaceans are divided into two major groups: those with teeth and those with baleen.

Baleen is a large filtration mechanism found in the mouths of most of the great whales (blue, fin, humpback, gray and several other species). Several hundred plates of baleen together make up a rack that hangs from each upper jaw, with a continuous layer of hair on the inside. Baleen whales engulf a large volume of water and prey — typically small fish or zooplankton — and then force the water out through the twin racks of baleen, trapping the food on the mat of hair inside before swallowing it.

Of the great whales, the only one with teeth is the sperm whale, a deep-diving species that is typically found in deep water and often far offshore; it would be very unusual to see a sperm whale venture into our waters.

The other toothed cetaceans include all the dolphins and porpoises, together with a large and enigmatic group known as the beaked whales. Like the sperm whale, don’t expect to see any of these around Vashon; they are mysterious animals that sometimes dive for more than two hours at a time, and to depths that in extreme cases are known to exceed 3,000 meters. Such feats by an air-breathing animal are extraordinary, and involve a remarkably complex physiology that allows them to survive while hunting for prey in complete darkness and under unimaginable pressure.

Currently, around 89 species of cetaceans are recognized by scientists, including some 16 species of baleen whales (“mysticetes”). Toothed whales (“odontocetes”) number 73 species, of which 24 are beaked whales.

The two groups are believed to have split around 34 million years ago, and today the oldest extant (surviving) species is likely the sperm whale, which may have been around for more than 20 million years. By the way, DNA analysis indicates that the closest living terrestrial relative to whales is the hippo.

There are other major differences between the two types of whales. The odontocetes (toothed whales) have a sophisticated echolocation (sonar) system that they use to navigate and find prey; there is no evidence for this in baleen whales. Because odontocetes use sonar, they appear to have lost their sense of smell; by contrast, studies of the brains of baleen whales strongly suggest that they are able to detect odors, and probably use this at the water surface to find patches of prey.

Many cetaceans are highly migratory. Some of the baleen whales undertake seasonal migrations that see them traveling over thousands of miles, from feeding grounds in colder waters to breeding and calving areas in tropical or subtropical latitudes. Some of them fast for weeks or months during the winter, replying on reserves of fat in their blubber to sustain them.

Sperm whales have a very different pattern. Females and juveniles largely remain in low latitudes; by contrast, mature males feed in cold polar waters and return occasionally to warmer waters to seek out mates.

The size range in cetaceans is huge. At one end, there’s a small porpoise named the vaquita, which measures at most just shy of five feet. The vaquita’s range today is confined to the upper Gulf of California in Mexico, and sadly the species is almost extinct.

At the other end of the size scale is the blue whale. At over 100 feet long and with a weight that likely approaches 200 tons, it may well be the largest animal ever to have existed on our planet. Blue whales also have what is probably the loudest voices in the animal kingdom: vocalizing at frequencies below the range of human hearing, their sounds can travel in excess of 2,000 miles in deep water. Whether blue whales actively communicate with each other over such vast distances is unknown.

All of the great whales have suffered terribly at the hands of whalers. In the 20th century, some three million were killed, and some species were reduced by more than 95% of their original numbers.

Happily, many whale populations are recovering well from this slaughter — though it’s not at all clear how they’ll fare in a future shaped by global warming.

In the next few articles, I’ll introduce you to our four most common “locals”: the humpback whale, gray whale, killer whale (orca), and the humble harbor porpoise.

Phil Clapham is a whale biologist who lives on Maury Island. Prior to retiring in 2019, he directed the Cetacean Assessment and Ecology Program at NOAA’s Alaska Fisheries Science Center in Seattle.