Cetaceans

Cetacean is a word used to describe all whales, dolphins and porpoises.  The word cetacean comes from the Latin word cetus, meaning “a large sea animal”, and the Greek word ketos, meaning ”sea monster”.  There are 80 cetacean species currently recognized, with several potentially new species pending.  Cetaceans range in size from the tiniest dolphin, Hector’s dolphin, just over 39 inches (1 m) long, to the largest whale, the Blue whale, which can be 100 feet (33 m) long.  The Blue whale is the largest animal ever to live on the Earth.  Cetaceans live in all oceans and many major rivers of the world.

Cetaceans are mammals, therefore they are endothermic (their internal body temperature remains the same regardless of the temperature of their surroundings), give birth to live young, breathe air through lungs instead of gills, and have hair at some point in their life.  They are believed to be ancestors of hoofed land mammals that lived about 50 million years ago. 

Characteristics

Cetaceans have several characteristics that allow us to tell species and individuals apart from one another and from fish species.  Most cetaceans have a dorsal fin, which can vary in size and shape.  Unlike fish, which propel themselves by moving their head to swing their tail from side-to-side, cetaceans use their tail in a smooth, powerful, up-and-down motion to propel their body through the water.

Cetaceans are voluntary breathers, meaning they have to think about when they breathe.  While humans basically breathe without thinking, a whale has to rise to the water’s surface at regular intervals to exhale and inhale through its blowholes.  When a whale comes to the surface to breathe, it exhales the air from its lungs (at a rate of 300 mph!) and then immediately inhales.  Cetaceans often surface for several breaths, and then dive below the surface again to feed, travel or perform other activities.

When a whale rises to the surface and exhales, the resulting cloud of water droplets seen in the air is referred to as the whale’s “blow” or “spout”.  Some whales have a visible blow, while others may have no visible blow at all.  The differences in blow size and shape often are a good clue to the type of whale you are observing, especially from a distance.

Types of Cetaceans

There are two main types of cetaceans – toothed whales, and baleen whales.  Toothed whales, or Odontocetes, include the pilot and sperm whales, belugas, orcas, and all the dolphins and porpoises.  When feeding, odontocetes use their teeth to catch a single fish or squid at a time. The teeth may rip or shred larger prey into manageable chunks, but they do not chew. Smaller prey are swallowed whole.

Baleen whales, or Mysticetes, include many of the whales we see in the Gulf of Maine, such as humpback, fin, minke and right whales.  Baleen whales have hundreds of fringed plates called baleen that hang from their upper jaw.  The plates lie next to each other, about ¼ inch apart, and are smooth on the outside, with stiff hairs on the inside.  The hairs of each plate overlap those of adjacent plates, forming a mesh-like strainer around the whale’s mouth.  Another name for baleen is “whalebone”, but it is not really bone at all.  It is made of keratin, the same material as your fingernails and hair.  Baleen was a highly desired commodity in past centuries for its many uses, such as in corsets, hoop skirts, brushes, buggy whips, lampshades and umbrellas.

Baleen whales feed by taking in large amounts of water containing thousands of small fish or crustaceans. They use their tongue and lower jaw to force the water out past the baleen plates.  This enables the whale to get rid of the salt water, which it cannot drink, while keeping its food on the inside of the baleen plates so it can be swallowed whole.  The crustaceans and fish that whales eat are full of protein, but since they are so tiny, a large cetacean, such as the fin whale (60-70’ long), must eat several tons of them a day to get its necessary nutrients.

Insulation

Unlike most mammals, whales do not have a coat of fur to keep them warm. Instead, they have a thick layer of insulating fat, called blubber, which lies between their skin and muscles. The thickness and distribution of blubber in a whale’s body varies among species, but the blubber layer in some whales can be up to 20 inches (50cm) thick.

One of the main reasons whales were hunted in the 17^th-19^th centuries was for their blubber.  This fat was boiled down to make oil that was used for lamps, to heat homes, for lubrication and even for cooking. Today, whales are hunted primarily for their meat, which is sold in local markets. The blubber is sometimes sold as a form of jerky, and in some rare cases, can be used as a low cost fuel.

Hearing

Whales compensate for a poor sense of smell and uncertain underwater visibility by having excellent hearing.  Whales do not have external ears, but they have tiny ear openings located behind each eye.  Unlike us, a whale can tell the direction of sound underwater.  Hearing plays a strong role in social dynamics of baleen and toothed whales, both of which communicate using sound.  Baleen whales probably use hearing alone to locate prey since they do not echolocate.   In all whales, eyesight probably does not play a large role in prey location, due to the variability of underwater visibility.

Diving

Most whales dive for a few minutes at a time, but some species can stay underwater for more than an hour!  Because species differ in size and lung capacity, diving times and patterns also vary between species. All whales have higher concentrations of hemoglobin and myoglobin in their blood and muscle tissues than do land mammals. These proteins bind and store oxygen throughout the whale’s body to allow it to stay underwater for longer times than land mammals could.

Behavior

There are several behaviors that whale observers may see: 

Breaching – a spectacular activity that occurs when a cetacean launches itself into the air and falls back into the water, either on its belly, back or side.  This may be the only time a whale watcher gets the opportunity to see a whale’s entire body.  Cetaceans may breach several times in a row, and when one animal breaches, others may follow.

Although there are several possible explanations for breaching, its cause is still something of a mystery.  It may be a sign of aggression or agitation, a courtship display, male competition for females, a form of acoustic signaling to other whales, a way to herd food or dislodge parasites, a way to clear the whale’s blowhole during rough water, or it may simply be for fun.  In fact, a combination of several factors may lead to breaching.

Lobtailing – when the whale slaps its tail flukes on the water, while most of its body is still underwater.  This is similar to “tail-breaching”, in which a whale throws the rear portion of its body out of the water and slaps it sideways onto the surface or on top of another whale.  This tail-breaching behavior may be a form of aggression in some species.

Lobtailing has also been recently documented as part of a feeding behavior, in which a humpback whale slaps its tail on the water to stun a school of fish, then dives under the school and engulfs the fish on its way back up.  This behavior is unique to Atlantic humpbacks and originated in the early 1980’s by a single female. It has since spread to a large portion of the population. 

Fluking – when a cetacean begins a dive, it lifts its tail in the air as its body angles down into the water.  This thrust of the tail helps the whale dive at a steeper angle so that it can go deeper more quickly.

 Sounding – when a cetacean dives with just a steep arch of its back and without showing its flukes.  Fin whales often “sound” when they dive, while humpback whales usually “fluke”.

Flipper-slapping – Also known as flipper-flopping or pectoral-slapping, this activity occurs when a whale rolls over at the water surface and slaps its flippers onto the water, creating a splash.  Humpback whales perform a variation of this by lying on their backs and waving both flippers in the air before slapping them both onto the surface of the water (this known as a “belly-up flipper-slap”!).

Even though whales and humans are both mammals and share many similarities, there are significant differences due to the challenges of living underwater.  A whale must keep itself warm in the cold ocean, compensate for the huge water pressure when it dives, and it must be able to reach the surface to breathe regularly.