Why learn about cetaceans?
“Because we are one of a kind! A long time ago we lived on land and looked like strange hippos! Then our ancestors decided that water would be our future home and so here we are to conquer you with our beauty!”
How we recognize cetaceans:
They are MAMMALS that live in water all their lives, they have developed specific adaptations, reaching dimensions among the largest in the animal kingdom, (the blue whale reaches 33 m and weighs 150 t):
We can immediately distinguish them from fish because they emerge to the surface to breathe.
“We have lungs like you and not gills like fish”
The orientation of the “tail” of cetaceans is very different from that of fish, in fact it is oriented on a horizontal plane with respect to the body.
“We move up and down and not left and right like fish!"
Cetaceans have a rostrum, that is, a more or less accentuated "snout" that seems to have an important role in echolocation. We will see...
They have a very elongated and hydrodynamic body.
They lost their hind limbs, strengthening their tail to the point where it became their means of locomotion.
They have a dorsal fin that is very different from species to species but is easy to spot when they remain on the surface to catch their breath.
"So you can easily recognize us by the shape of our fin!"
They do not have hair but many tactile receptors concentrated in the most sensitive areas such as the head, fins and around the genitals.
They have a large amount of body fat: it limits heat loss, shapes the body and helps with buoyancy.
The skeleton no longer serves as support as in land mammals, which is also why animals have reached enormous dimensions.
“We don’t have to bear our weight like you on earth.”
What do cetaceans eat:
Cetaceans are divided into:
Mysticetes (=whacked cetaceans) feed on plankton, especially krill or small fish. They are the largest living beings in the world.
Mysticeti do not have teeth and feed through baleen, many thick combs (that look like whiskers) specialized in filtering plankton. They have a jagged internal edge (which filters the plankton) and a smooth external edge (which lets the filtered water out).
“They are made of keratin like your nails and hair!”
For greater filtration efficiency, mysticetes are equipped with throat grooves that allow the throat skin to expand enormously and filter large quantities of water.
“A kind of accordion that we open when we swallow water and close when we filter it!”
Odontocetes (=cetaceans with teeth) are active hunters that feed on fish, cephalopods, other mammals.
“You surely know us: we are the killer whales, the dolphins, the sperm whales and many others!”
The life of cetaceans:
The delicate life cycle of cetaceans is their Achilles heel: despite being animals that live a long time, their young are subject to many dangers and above all, the mother gives birth to very few in her lifetime.
Let's see...
They reach sexual maturity around 6-12 years of age with some differences between males and females.
Matings are short-lived, take place belly to belly and are preceded by complex courtship displays and competitions between males.
The gestation period of Mysticetes lasts an average of 12 months, while that of Odontocetes is more variable, depending on the size of the animal.
During birth, the young come out through the tail end so that they don't drown before they are completely out.
As soon as they are born they are able to swim and are helped by their mother to reach the surface for their first breath.
The babies, usually one per litter, are unable to suck milk (they have no lips), so the mother sprays it directly into their mouths. However, the milk is much richer in fat than human milk and much thicker to avoid mixing with salt water.
Weaning occurs after several months but the cubs will remain with their mothers until adulthood.
Some species create very large groups that will remain together for their entire lives.
How to determine the age of a cetacean:
All cetaceans produce earwax, over time this earwax accumulates and creates a sort of plug that is positioned in the auditory canal of the external ear. The plug has black and white layers. The dark layer has been associated with the migratory period in which the cetacean does not feed. By counting the migrations, the age of the cetacean can be traced.
Examples of ages: fin whale 80/90 years, right whale 65 years, sperm whale 70 years.
“Small curiosities to learn more about our world”
Breathing:
Cetaceans breathe through their lungs and expel air through a blowhole equipped with valves that close hermetically when they dive. The blowhole, when it opens on the surface, produces a murmur (given by the exhaled air, heated by the lungs) visible even from a distance and different from species to species. Cetaceans have different apnea times, depending greatly on their habits and diet. Their lungs, on average proportional to the body, have the ability to collapse almost completely as the depth increases. This characteristic allows them to avoid dangerous accumulations of nitrogen in the blood, which could lead to the onset of decompression sickness or nitrogen narcosis, diseases well known to divers.
Communication and echolocation:
Cetaceans emit sound signals in the water both to communicate between individuals and for orientation. They communicate with low frequencies: ultrasound, inaudible to humans (between 30 and 120 kHz).
Echolocation, on the other hand, is typical of odontocetes, it is a transmission of sound impulses through the production of clicks and returning echoes. This received and re-elaborated echo leads to knowledge of the surrounding environment, proving very useful for hunting or identifying any obstacles.
“We hear very well: we perceive the direction of the sound and we recognize it perfectly, unlike you humans underwater!”
Sight
Cetaceans have a flexible lens (unlike terrestrial mammals) and can see both on the surface and under water. Their eyesight seems fair with limited color vision.
The enemies of cetaceans:
Sharks and two species of mammals are the most dangerous enemies. The first species is the orca that, hunting in highly organized and coordinated groups, creates real hunting trips for baby whales and whales in difficulty.
The second is man, the most fearsome of all. Collisions with boats, noise pollution, marine pollution from plastics and waste, entrapment in abandoned fishing nets, captivity and clearly the reckless and useless fishing of these splendid animals are just a few examples.
Not only have they caused the collapse of cetacean populations worldwide but they have destroyed entire families with deep bonds, more than any other being on Earth.
A moment of reflection... Cetaceans experience complex emotions
They have a highly developed brain, whose relative size is comparable to that of anthropomorphic primates, including humans; and like them they have spindle cells or von Economo neurons.
These cells are very large neurons that apparently play a role in empathy and intuition of feelings. They have been found in humpback whales, fin whales, killer whales, sperm whales, in the same brain areas as their human counterparts but in three times greater numbers.
These cells are nothing but a confirmation of their extraordinarily loving and empathetic behaviors: cetaceans are among the most intelligent animals on Earth and among the most sensitive in social relationships.
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