The Secret Existence of Cetaceans

To celebrate the World Ocean Day, we are displaying a series of colouring pages available altogether in a downloadable format.

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The Secret Existence of Cetaceans

Discover the different cetacean species through colouring and writing down their names and curious facts. Use your creativity to learn faster! Illustrations by Aja Trebec in collaboration with Entire Ocean © Aja Trebec, June 2021


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Sperm whale

Physeter macrocephalus

Sperm whales have the largest bony head among the whale species that holds an immense frontal echolocation organ. In order to avoid the constant pressure of swimming, sperm whales sleep vertically for approximately 15 minutes. By doing it more times, this behaviour is thought to cover around 7% of their day.

Pilot whale

Globicephala macrorhynchus

Pilot whales swim together in large social groups called pods. Age and sex of individuals within the pod are variable. However, adult females prevail over males. Interestingly and quite unusual is the fact that adult males do not abandon their natal pod nor mate. This altruistic behaviour is believed to support the survival of a relative or other individual, and thus, enhances the propagation of shared genes.

Baleen of Bowhead whale

Balaena mysticetus

The bowhead whale has a filter-feeding system called ballen. In fact, its baleen is the longest among the rest of baleen whales. By letting a high amount of water into the mouth, the bowhead whale then closes the baleen and compresses the water out, trapping small animals such as krill. Baleen is made of keratin, a fibrous structural protein, that is found also in our hair, nail and skin.

Ventral groove blubber of a Humpback whale

Megaptera novaeangliae

The stretchy tissue that runs from the snout to the umbilicus of a humpback whale is called the ventral groove blubber. When the animal is feeding, it lowers its jaw and swims quickly, which causes the blubber to expand and enclose an enormous volume of water that may be bigger than the whale itself.

Whale barnacles

Barnacles are small sessile organisms related to crabs and lobsters, that tend to attach to baleen whales, and therefore, establish a commensal relationship. The barnacles benefit from the whale by obtaining support and food that they filter while the whale is in motion. The whale, on the other hand, neither benefits nor gets harmed.

Southern right whale dolphin

Lissodelphis peronii

The southern right whale dolphin is perhaps one of the most mysterious dolphin species we know. This energetic swimmer is characterised by the lack of a dorsal fin and distinctive colours, having a black back and a white belly. Although it prefers to swim in the depths of the sub-Antarctic region, it sometimes travels in pods of about 100 animals resembling a herd of penguins.


Monodon monoceros

Having no dorsal fin, the narwhal prevents the heat loss, which allows it to swim under ice sheets of the Arctic regions. Another morphological feature typical of males is the presence of a tusk that is a sensory organ with numerous nerve endings. Apart from using it for feeding, males communicate information through the act of rubbing one tusk against the other.

Irrawaddy dolphin

Orcaella brevirostris

The irrawaddy dolphin is euryhaline, meaning that it can tolerate a wide range of salinity, and can thus transition from coastal marine environments towards freshwater environments. This species inhabits waters of Papua New Guinea, the Philippines and the Bay of Bengal, sticking within a limited group of individuals, in which it shows quite a social behaviour. Together with its mates, they encircle fish and cephalopods by spitting water up to 1,5m away.

Risso’s dolphin

Grampus griseus

Reaching up to 4m in length, the risso’s dolphin is more closely related to false killer and pilot whales, than to other species of dolphins. With age, this species appears to become an expertised warrior, because its body becomes progressively scarred from social interactions with their prey and other whales.

Killer whale

Orcinus orca

Sometimes called the wolves of the sea, these enormous top predators are not whales, rather they are the biggest oceanic dolphins in the world. Surprisingly, orcas share some pretty interesting facts with humans. One of them is that distinctive genes among different orca clans correspond to distinctive culture, like social behaviours and different languages. They are the most widespread mammals after humans, found from the Arctic to the Antarctic.

The social structure of killer whales

Orcinus orca

Killer whales live in pods, in which they remain from their birth on. For this reason, older females go through menopause in order to avoid sharing too many genes with the rest of the pod members. This is also why older females focus more on guiding and teaching their children, grandchildren and great-grandchildren.

Bottlenose dolphin

Tursiops spp.

These conscious breathers have a particular way of taking naps. While they control what is going on in the environment and their breathing functions with one half of their brain, the other half is shut in order to sleep. So even though they appear very active, resurfacing about every 7 minutes, they actually rest for approximately 2 hours and then change the brain’s hemisphere, to rest some more, which is called cat-napping.

Rough-toothed dolphin

Steno bredanensis

Unlike any other dolphin species that has a rounded head featured by a melon, the rough-toothed dolphin has a more pointed head and snout. Its skin is mainly silver with occasional paler spots mainly distributed on the ventral part of the body. This species stays in the deeper warm waters where it chases squid, octopus and fish with its jaggedly ridged choppers.

Fin whale

Balaenoptera physalus

Reaching up to 24 meters in length, the fin whale is the second largest whale species in the world and the largest found in the Mediterranean Sea. It eats up to 1,8 tons of food per day which helps it maintain its energy demands. The fin whale also has an incredibly long life because it can live between 80 to 90 years.

Common dolphin

Delphis sp.

Although distinguished in long- and short-beaked species, the common dolphin is widely distributed around the world’s oceans. It is an active species, an impeccable swimmer that swishes through the water 60 km/h and is commonly seen performing aerial acrobatics around boats and even baleen whales. This swimming behaviour is called bow riding and. In addition, the common dolphin lives in aggregations of thousands of individuals of the same species, and sometimes, it associates to other dolphin species (e.g. pilot whales).

Common short-beaked dolphins have been observed to engage in oral sex, thus suggesting that they, just like chimpanzees and humans, get involved in sexual activities for pleasure.

Beluga whale

Delphinapterus leucas

The beluga whale lives in the Arctic and sub-Arctic regions and is closely related to the narwhal. This “white dolphin without a wing” is an extremely sociable whale species that can change its face expression thanks to a flexible melon found in the head. It can modify the shape of the melon and consequently create different sound effects, such as clicks, whistles, squeals and chirps. This is also why people have been referring to this species as the canary of the sea.

Commerson’s dolphin

Cephalorhynchus commersonii

The smallest cetaceans in the world are the Commerson’s dolphins. Females are usually a bit bigger than males and they only reach up to 1,6 meters in length. Individuals of this species have their anterior and posterior part coloured in black, whereas the middle is white. They are found swimming in groups of two to three hundreds, thus implying that they are a social species of dolphins. Also because they are sometimes seen interacting with humans in a friendly and playful way.

Blue whale

Balaenoptera musculus

Almost 30 meters in length, the blue whale is the biggest animal of the world’s oceans. Its massiveness comes from eating up to 36 tonnes per day of small organisms called krill. Normally, the blue whale swims alone or in pairs, forming a strong attachment.

Even though it cannot be heard by the human ear, the blue whale emits a series of strong frequency pulses and moans, communicating up to 1600 km away.