Cetaceans are mammals that have adapted to aquatic life and live exclusively in the water.
The term Cetacea in biological terms means whale or (originally) large sea animal.
There are three types of marine mammals that compose the cetacean species which include whales, dolphins and porpoises.
Although the term whale can be used to refer to all cetaceans it usually excludes dolphins and porpoises in order to avoid confusion among the three primary species.
Depending on their physical features cetaceans can be broken down further into two primary suborders which are known as the (Odontoceti) toothed whale and (Mysticeti) baleen whale suborders.
Overall there around currently around 90 known species of cetacean recorded so far.
Toothed Whale Cetaceans
As the name suggest cetaceans that are born with teeth are part of the toothed whale suborder, and because they have teeth these marine mammals are considered the active hunters of the two suborders.
In addition to whales the toothed whale suborder also consists of all species of dolphin and porpoise as both of these marine mammals also possess teeth.
Cetaceans that belong to the toothed whale suborder are known to eat prey such as fish, squid, octopus and crustaceans, however there are a few species such as the killer whale and false killer whale that are known to consume larger prey such as sea lions, seabirds, penguins, dolphins and even large whales.
In addition to having teeth toothed whales also possess echolocation which helps them navigate the ocean and search for prey.
The echolocation in these marine mammals is extremely advanced and allows them to determine the size, speed, direction, elevation and density of the objects around them so that they can tell if its food, a predator or an inanimate object.
Toothed whales may also use their echolocation abilities to communicate with other pod members and organize attacks on the prey they are hunting.
In order to communicate with one another toothed whales use high pitched clicks and whistles.
While we do not know much about their communication it is likely that these sounds are used to inform others of local food, coordinate hunting methods, communicate a desire to mate and socialize with other pod members.
When it comes to size toothed whales are typically smaller than baleen whales, with the exception of the sperm whale (the largest of the toothed whale species).
Toothed whale cetaceans can vary in size from 4 ft. Maui’s dolphin all the way up to 67 ft. the sperm whale.
Baleen Whale Cetaceans
Baleen whales are the larger cetaceans and is comprised solely of large whales (there are no dolphins or porpoises on the baleen whale suborder).
Rather than having teeth these marine mammals possess baleen plates and their plates have many fine bristles attached to them which can be visually compared to the bristles of a comb.
Since they aren’t able to attack their prey with teeth they hunt by swimming with their mouth open sucking up water, sediments and small prey such as krill, shrimp, fish and other small aquatic life forms.
Once they’ve captured enough prey they will then expel the water from their mouth with their tongue leaving their prey trapped in their baleen bristles.
This method of hunting is also referred to as filter feeding as their baleen bristles help them filter their prey from the water by acting like a fence that allows water to pass in and out will prevent its prey from escaping.
While these marine mammals are larger than their toothed whale relatives their size does not determine what types of food they will eat.
For example the killer whale (actually a dolphin) has been known to hunt both sharks and whales while the blue whale (the largest living animal and part of the baleen whale suborder) survives on a diet primarily composed of small krill that averages less than 2 inches in size.
While baleen whales tend to consume very small prey that is easily digestible they can consume thousands or even millions of their prey in a single day.
Using the blue whale as an example again these marine mammals survive on much smaller prey than the killer whale however a single adult blue whale may consume up to 40 million krill on any given day.
Cetacean Marine Mammal Characteristics and Features
Several characteristics are apparent among all cetacean species.
Unlike fish cetaceans must breathe air in order to survive and most species cannot stay submerged underwater more than an 90 minutes without coming up for fresh air.
Depending in their suborder cetaceans either have one or two blowhole which they use to breathe.
The smaller toothed whale species are born with a single blowhole instead of two.
While the reason for this is unknown it is believed that one of their blowholes developed into part of their echolocation system in order to help them detect nearby prey, avoid predators and navigate the ocean in dark areas.
All cetaceans are considered conscious breathers which means they are always aware of their need for oxygen and never fall completely asleep because if they did there is a chance they would sink and drown or be attacked by an unsuspecting predator.
When looking at cetaceans from an evolutionary standpoint these marine mammals appear to have originated from land dwelling animals.
The bones found in a cetaceans flippers indicate the previous existence of limbs which their ancestors used to walk and hunt on land before they evolved into completely aquatic animals.
Their spines also show previous signs of their land dwelling origins.
Instead of moving their bodies from left to right to move through the ocean as fish do, the curvature and function of the whales spine appears to be designed more for running as they can be seen arching their backs, and moving their tail and flukes up and down rather than from left to right.
In order to stay warm cetaceans have a thick layer of blubber which helps them insulate heat while in cold/polar environments and helps keeps them warm during feeding seasons which for some species are in the colder regions of the ocean.
During mating season which usually occurs during the colder winter months of the year the cetaceans blubber may be converted into energy as the whales migrate toward the equator.
Some species of whale are known to fast when migrating living completely off of energy stored in their blubber during feeding season.
While all cetaceans have blubber most species are hairless or at least mostly hairless.
Cetaceans that do possess hair lose it shortly after birth, however they may still maintain their hair follicles even after losing their hair.