Oceans are the planet’s blue wilderness and like their greener, terrestrial counterparts, are constructed of intricate food webs and myriad unique species of varying sizes, shapes and colours. The colour of water and the refraction of light render marine ecosystems visually enchanting, especially when experienced from below the surface through a scuba mask. Like land-based ecosystems, the top of the marine foodchain is occupied by megafauna, the likes of dolphins, whales, dugongs, sharks and sea lions. These species are unique, beautiful, graceful, playful or mysterious so there is little wonder they capture our imaginations. Marine birdlife and marine reptiles (like sea turtles or marine iguanas) also have an uncanny charisma thanks to comical physical traits and often outrageous breeding behaviours.
Marine megafauna
AND OTHER AMAZING CREATURES FROM THE BIG BLUE
Giants of the deep
DISCOVER THE MARINE WORLD
SIGHTINGS
PHOTO GALLERY
INFORMATION
A pod of dolphins or whales
At a glance
LONGEST
LEATHERBACK TURTLES CAN MIGRATE 16,000 KMPA
HEAVIEST
Blue whales can weigh 200 tons
CALVES
Dolphin calves stay with mom for 7 yrs
GENDER REVEAL
TURTLE HATCHLINGS' SEX IS DETERMINED BY TEMPERATURE
LONGEVITY
CORALS ARE THE LONGEST LIVING ANIMALS (4000 YR-OLD SPP)
STRANGE DIETS
ENORMOUS WHALES ARE SUSTAINED BY MINISCULE ZOOPLANTON
Get to know marine megafauna
Did you know?
Dolphins sleep with half a brain
In a process known as “unihemispheric slow-wave sleep,” dolphins sleep by shutting off one hemisphere of their brains at a time, while closing the eye on the opposite side
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in order to continue monitoring what’s going on around them and to regulate their breathing while they snooze.
Dolphins can have hundreds of teeth
However, they mostly swallow their food whole and do not actually chew even though they are carnivorous eating fish, squid, octopus, crustaceans etc.
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Teeth are primarily used in defence or to grip objects. Dolphins are extremely intelligent and live in complex societies that use complex communication. They often work together to catch prey by encircling it and forcing fish into a small, dense ball and then taking turns to swim through the baitball to pick off the trapped prey. Some species force their prey into shallow water and then attack. Dolphins have a stomach for storing food and another one for digesting it.
Dolphins swim super fast
Clocking speeds of up to 40 kmph (or 25 mph) when they’re in pursuit of prey or fun, dolphins can swim extremely rapidly using their tails (or flukes) to trust them forward.
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Their normal swimming speed is about 12 kmph (or 8 mph). The tail or fluke is very flexible with dolphins being able to control that flexibility somehow, to generate the force that pushes them forward or up and out of the water. Most dolphins can stay underwater for around 10 minutes, but some species even up to 15 minutes. They breathe through a blowhole, covered by a muscular flap when they go under the surface, preventing water from entering into their lungs.
Some whales are actually dolphins
Obvious from their black and white colouring and large size, orcas are actually dolphins and not whales. Often known as killer whales, they are the biggest members
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of the dolphin family and found across the world. Like the other members of their family, they are very intelligent and able to communicate in complex ways, coordinating with each other to hunt their prey.
Calves suckle milk from their mothers
Female dolphins have inverted nipples which come out with stimulation by the baby, milk ejecting into the baby’s mouth, while it holds its mouth and/or tongue around the nipple.
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Dolphins usually only just one calf that remains with them for the first seven years of life, the kind of long-term family bond only really typical for mammals like elephants, or primates. To maintain their communal society, dolphins are very social and altruistic, helping the injured to reach the surface to breathe, for example. They are also known to help other animals and even humans in need.
There are dolphins in the Amazon River
Also known as the “Boto”, Amazon dolphins are one of more than 40 species of dolphin found on earth and they usually have pink skin, which flushes redder at times.
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They live in smaller groups than marine dolphins but are one of the larger dolphin species and they are also more agile than other species. Vertebrae in the neck aren’t fused enabling them to twist their heads 180 degrees and to navigate underwater obstacles like tree trunks and rocks.
Did you know?
Turtles maintain marine ecosystems
Grazing on seagrass beds and sea sponges on coral reefs, turtles prevent overgrowth and thus improve current flows and nitrogen production.
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This then promotes the healthy cultivation of marine flora and fauna. Some turtles also eat jellyfish and crustaceans thereby controlling those population numbers. They also provide sustenance for barnacles, algae, and small organisms that cling to their shells. All these positive feedback loops and nutrient cycling are vital for marine habitat. The migratory habits of turtles also see them transporting nitrogen, phosphorus, and potassium from the sea to the beaches they nest on.
Turtles live a very long time
While it is difficult to document the exact age of of sea turtles, scientists have discovered that turtles have a similar life span to people.
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Marine turtles can take as many two to three decades to mature and are actively reproductive for at least another decade. The most consistent estimates show that some species of turtle live for 70 to 80 years.
Turtles migrate many miles
Turtles migrate long distances during their lives, moving from high seas to nesting beaches and back. Leatherbacks, for example, can travel 16,000 km (10,000 mi) or more annually.
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Loggerheads have been recorded covering about 13,000 km (8,000 mi). Green turtles and olive ridleys are more sedentary, staying close to home and completing much shorter migrations. While it is difficult to calculate the exact number of sea turtles left in the wild, scientists estimate thereto be around 6.5 million so most species are listed as endangered or critically endangered and the number of individuals remaining varies significantly.
Sand temperature determines gender
The temperature of the sand in which turtle eggs are laid determines the hatchlings’ sex with cooler incubation temperatures producing males and warmer, females.
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The eggs of marine turtles care laid in a nest the female digs in the sand on the beach with their rear flippers. She lays 100 to 125 eggs at a time, and may nest multiple times over several months. If temperatures fluctuation during the two-month incubationa mix of male and female turtles is likely, otherwise, depending on prevailing weather conditions, the depth at which the eggs lie will govern the sex.
Sea turtles don’t retract into shells
The shell is part of a turtle’s skeleton, adapted from the ribs and covered in tough skin and they cannot retract their paddle-shaped flippers and head into their shells like tortoises.
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While their shells do provide protection from enemies and the elements, the fact that they cannot fully retract makes them vulnerable to predators such as tiger sharks and killer whales (and land predators).
Did you know?
Whales are the opera singers of the sea
Whales’ songs are long, patterned sequences of sounds which are not genetically hard-wired like mating calls of other animals but rather they are complex compilations learned from other whales.
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Whales are social, air breathing mammals, they feed their babies with their own milk, and they take extraordinarily good care of their young, teaching them life skills. Blue whales, fin whales, bowhead whales, minke whales, sperm whales and humpback whales all sing. Humpback whale songs have even appeared in the album charts.
Whales are divided into two groups
There are two types of whales; the baleen whales (with 14 species) and the toothed whales (with 76 species). The main difference between the two are the food they eat and how they eat.
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Baleen whales have baleen plates, or filtering sheets which strain out small organisms like krill and plankton and algae from the ocean. Toothed whales have teeth and prey on fish, squid and other larger marine animals. Humpback whales in the southern hemisphere can go without food for nearly 8 months fasting in order to allow them to allocate all of their energy to migration and reproduction. These huge whales hunt and feed aggressively during the summer months, eating up to 1350 kg per day, and then during the winter, they use their “blubber” reserves while migrating and mating.
A whale’s tail is its fingerprint
No two whale tails are alike rather, every whale’s tail is unique and an individual is identifiable by the patterns and grooves on the undersides of its tail.
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Characteristics like slits, grooves, and brown algae spots gained over time through wear and tear are not replicable.
Whales can leap right out of the water
Enormous as they are, whales can lift their entire bodies completely out of the water in a jump known as “breaching”. Both whales and dolphins do this.
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Humpback whales are the most acrobatic of all the larger species. When they launch their 40 ton bodies out of the water, it is nothing short of spectacular. Whales breach to communicate to others in their pod (the splash from the jump can be heard a long distance away underwater). It can also signal excitement, dominance, mating intentions, warnings, or changes in direction. They also orientate to the coastline during migration through the process of breaching.
Whales can’t breathe underwater
Cetaceans, like whales and dolphins, have lungs for breathing air and they can’t breathe underwater. The blowhole on the tops of their heads is used for breathing.
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Despite their inability to breathe underwater, whales and dolphins are both able to hold their breath for long periods. The longest recorded dive by a whale was 137 minutes long. Baleen and toothed whales differ in the number of blowholes they have – baleen whales have two, while toothed whales only have one.
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