The Animals of the Great Barrier Reef

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The largest coral reef in the world, the Great Barrier Reef off the northeastern coast of Australia consists of more than 2,900 coral reefs, 600 continental islands, 300 coral cays and thousands of animal species, making it one of the world's most complex ecosystems. The animals that call the Great Barrier Reef home include fish, corals, mollusks, echinoderms, sea snakes, marine turtles, sponges, whales and dolphins, and seabirds and shorebirds. On the following slides, we explore this diverse array of fauna in more detail. 

Hard Coral

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The Great Barrier Reef is home to about 360 species of hard coral, including bottlebrush coral, bubble coral, brain coral, mushroom coral, staghorn coral, tabletop coral and needle coral. Also known as stony corals, hard corals congregate in shallow tropical waters and help build the structure of coral reefs, growing in various types of aggregations, including mounds, plates, and branches. As previous coral colonies die, new ones grow on top of the limestone skeletons of their predecessors, creating the reef's three-dimensional architecture.  


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Although they're not quite as visible as other animals, the 5,000 or so species of sponges along the Great Barrier Reef perform an essential ecological function: they occupy a position near the base of the food chain, providing nutrients for more complex animals, and some species help to recycle calcium carbonate from dying corals, thus paving the way for new generations and maintaining the reef's overall health (the calcium carbonate thus freed also winds up being incorporated into the bodies of mollusks and diatoms).

Starfish and Sea Cucumbers

The crown-of-thorns starfish. Getty Images

The Great Barrier Reef's 600 or so species of echinoderms—the order of animals that includes starfish, sea stars and sea cucumbers—are mostly good citizens, constituting an essential link in the food chain and helping maintain the reef's overall ecology. The exception is the crown-of-thorns starfish, which feeds on the soft tissues of corals and can cause a drastic decline in coral populations if left unchecked; the only reliable remedy is maintaining populations of the crown-of-thorn's natural predators, including the giant triton snail and the starry puffer fish.


The Giant Clam. Getty Images

Mollusks are a widely divergent order of animals, including species as different in appearance and behavior as clams, oysters and cuttlefish. As far as marine biologists can tell, there are at least 5,000 and possibly as many as 10,000 species of mollusks inhabiting the Great Barrier Reef, the most visible of which is the giant clam, which can weigh as much as 500 pounds. This ecosystem is also notable for its zig-zag oysters, octopuses and squids, cowries (which were once used as money by Australia's indigenous human tribes), bivalves and sea slugs.


A clownfish of the Great Barrier Reef. Getty Images

The more than 1,500 species of fish inhabiting the Great Barrier Reef range in size from tiny gobies, to larger bony fishes (such as tuskfish and potato cods), all the way to massive cartilaginous fish like manta rays, tiger sharks and whale sharks. Damselfish, wrasses and tuskfish are among the most abundant fish on the reef; there are also blennies, butterfly fish, triggerfish, cowfish, pufferfish, angelfish, anemone fish, coral trout, seahorses, sea perch, sole, scorpion fish, hawkfish and surgeonfish.       

Sea Turtles

A hawksbill turtle. Getty Images

Seven species of sea turtle are known to frequent the Great Barrier Reef: the green turtle, the loggerhead turtle, the hawksbill turtle, the flatback turtle, the Pacific ridley turtle and (less frequently) the leatherback turtle. Green, loggerhead and hawksbill turtles nest on coral cays, while flatback turtles prefer continental islands and the green and leatherback turtles reside on mainland Australia, only occasionally foraging as far out as the Great Barrier Reef. All of these turtles, like many animals of the reef, are currently classified as either vulnerable or endangered.

Sea Snakes

A banded sea snake. Getty Images

About 30 million years ago, a population of terrestrial Australian snakes ventured hesitantly toward the sea. Today, there are about 15 sea snakes endemic to the Great Barrier Reef, including the large olive sea snake and the banded sea krait. Like all reptiles, sea snakes are equipped with lungs, but they can also absorb a small amount of oxygen from water, and possess specialized glands that excrete excess salt. All sea snake species are venomous, but present much less of a threat to humans compared to terrestrial species like cobras and copperheads.


A reef egret. Getty Images

Wherever there are fish and molluscs, you can be sure to find pelagic birds, which nest on nearby islands or the Australian coastline and venture out to the Great Barrier Reef for their frequent meals. On Heron Island alone, you can find birds as diverse (and as allusively named) as the bar-shouldered dove, the black-faced cuckoo shrike, the capricorn silver eye, the buff-banded rail, the sacred kingfisher, the silver gull, the eastern reef egret, and the white-bellied sea eagle, all of which rely on the nearby reef for their daily nutritional requirements.

Dolphins and Whales

The dwarf minke whale. Getty Images

The relatively warm waters of the Great Barrier Reef make it a favored destination for about 30 species of dolphins and whales, some of which ply these waters virtually year-round, some of which swim to this region to give birth and raise young, and some of which simply pass through during their annual migrations. The most spectacular (and most entertaining) cetacean of the Great Barrier Reef is the humpbacked whale; lucky visitors can also catch glimpses of the five-ton dwarf minke whale and the bottlenose dolphin, which likes to travel in groups.


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Dugongs—which may or may not be the source of the mermaid myth—are often thought to be closely related to dolphins and whales, but in fact, they share a "last common ancestor" with modern elephants. These large, vaguely comical-looking mammals are strictly herbivorous, feeding on the numerous aquatic plants of the Great Barrier Reef, and are hunted by sharks and saltwater crocodiles (which venture into this region only occasionally but with bloody consequences). Today, there are believed to be upwards of 50,000 dugongs in the vicinity of Australia, an encouraging upturn in numbers for this still-endangered sirenian.