Last weekend marked World Oceans Day, a day dedicated to celebrating the beauty and bounty that our oceans provide, and raising awareness of the importance of protecting them. Here at ARKive, we’ve been inspired by the watery realm, and thought we’d honour our fellow mammals by submerging ourselves in the wonderful world of whales and dolphins.
An instantly recognisable species, the humpback whale is named for the distinctive ‘hump’ formed by its back as it prepares to dive. Its long flippers, another characteristic feature, can grow up to five metres in length, and contribute to this vocal cetacean’s scientific name, Megaptera novaeangliae, which means ‘big-winged New Englander’.
Orcas are easily distinguishable by their striking black and white markings and their imposing, triangular dorsal fin. Interestingly, these fascinating marine mammals have a rather misleading alternative name – killer whales. While they are certainly efficient predators, they are not whales and are, in fact, the largest members of the dolphin family. Orcas usually hunt in pods, although individuals from some populations are known to deliberately beach themselves in order to snatch sea lions resting on the beach before wriggling back to sea with their prey.
The charismatic dusky dolphin is a highly social species, sometimes being found in pods of over 1,000 individuals and frequently associating with other cetacean species. This beautiful marine mammal is said to be one of the most acrobatic of all dolphins, often making energetic leaps out of the water and performing impressive tumbles in the air.
There’s no mistaking the unique narwhal, a species famed for the hugely elongated tooth or ‘tusk’ which protrudes from its upper lip. The longest of these incredible appendages was recorded at over 2.5 metres in length, and the males use these bodily weapons in jousting bouts. The narwhal is found throughout the waters of the Arctic, as well as in the northern Atlantic Ocean, and it tends to stay close to pack ice.
Quite possibly the most famous of all cetaceans, the bottlenose dolphin is much-loved by many. This extremely intelligent species is highly social, and uses a wide range of clicks and whistles to communicate with other members of its pod. Like some other species of cetacean, the bottlenose dolphin seeks out prey using echolocation, and individuals in a pod will work together as a team to round up schools of fish into tight balls upon which the dolphins can feed. When not chasing prey or performing impressive leaps, dolphins are able to rest one side of their brain at a time. This allows them to sleep while remaining conscious enough to surface and breathe.
The strange-looking sperm whale can be forgiven for having such a bulbous head, given that it has the largest and heaviest brain of any living animal! And its record-breaking statistics don’t stop there – capable of diving for up to two hours at a time, the sperm whale can dive to depths of 3,000 metres, making it the deepest-diving mammal. The largest of the toothed whales, the sperm whale is famed in literature as Herman Melville’s Moby Dick, but sadly it is classified as Vulnerable on the IUCN Red List, primarily as a result of historic and present-day hunting.
A somewhat unusual-looking mammal, Risso’s dolphin can be identified by its long, pointed flippers, bulbous, beakless head, and the conspicuous scars present all over its body. These markings are thought to be caused by bites from other individuals of its kind during playing or fighting, but some scars could be the result of squid bites.
Although it is also known as the white whale, the beluga whale is actually born with dark grey to bluish- or brownish-grey colouration, only achieving the striking white hue as it matures. It is one of just a few cetaceans with a flexible neck, and it is capable of pursing its lips to suck up prey. The beluga whale is sometimes referred to as the sea canary because of the high-pitched twittering noises it produces.
On the brink
The baiji, or Yangtze River dolphin, is a very shy and graceful freshwater dolphin species with a very long, narrow, slightly upturned beak and small eyes placed high on the face. Sadly, it is thought that the Critically Endangered baiji could actually now be extinct. In 1999, only four individuals of its kind were observed, and an intensive search of its range in 2006 resulted in none being seen. The major threats to the baiji are considered to be illegal fishing using electricity, and being caught as bycatch in fishing nets.
We couldn’t possibly finish this round-up of ten incredible cetaceans without including the biggest of them all – the blue whale! The biggest animal to have ever lived, the blue whale has a heart the size of a small car and is capable of eating more than 4 tonnes of krill per day during the summer months. Whereas some cetacean species communicate using a series of high-pitched clicks and whistles, the blue whale produces a variety of low-frequency sounds, which may also serve the purpose of sensing the environment and detecting prey.
Is your favourite whale or dolphin not featured here? Then why not comment below to let us know what it is and why you love it!
If you’re looking for a fun challenge, check out ARKive’s ocean-themed scavenger hunt – there may well be a few cetaceans hidden in there!
Find out more about whale and dolphin conservation:
Kathryn Pintus, ARKive Text Author