The Animals of the Great Barrier Reef

Meet the corals, kraits, and dugongs that live here and help maintain the reef

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. These animals include fish, corals, mollusks, echinoderms, sea snakes, marine turtles, sponges, whales, dolphins, seabirds, and shorebirds. Here are details on this diverse array of fauna:

Hard Coral

Heron Island Underwater Collection
Colin Baker / Getty Images

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 coral reefs, growing in various aggregations including mounds, plates, and branches. As coral colonies die, new ones grow atop the limestone skeletons of their predecessors, creating the reef's three-dimensional architecture.

Sponges

Heron Island Underwater Collection
Colin Baker / Getty Images

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

Starfish and Sea Cucumbers

Lodestone Reef, Great Barrier Reef, Australia
Joao Inacio / Getty Images

The Great Barrier Reef's 600 or so species of echinoderms—the order 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 drastic declines 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.

Mollusks

Maxima clam (Tridacna maxima), Great Barrier Reef, Queensland
Michael Szonyi / Getty Images

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

Fish

Clownfish in anemone on the Great Barrier Reef
Kevin Boutwell / Getty Images

The more than 1,500 species of fish inhabiting the Great Barrier Reef range from tiny gobies and larger bony fishes, such as tuskfish and potato cods, up to massive cartilaginous fish such as 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

Green Turtle Swimming Over Coral
Vicki Smith / Getty Images

Seven species of sea turtles frequent the Great Barrier Reef: the green turtle, loggerhead turtle, hawksbill turtle, flatback turtle, Pacific ridley turtle, and 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 these turtles, like many animals of the reef, are currently classified as either vulnerable or endangered.

Sea Snakes

Olive Sea Snake
Brandi Mueller / Getty Images

About 30 million years ago, a population of terrestrial Australian snakes ventured hesitantly toward the sea. Today, about 15 sea snakes are 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 absorb a small amount of oxygen from water and have specialized glands that excrete excess salt. All sea snake species are venomous but are much less of a threat to humans than terrestrial species such as cobras and copperheads.

Birds

Roseate Tern with baby under its wing Lady Elliot
Darrell Gulin / Getty Images

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

Dolphins and Whales

Curious adult dwarf minke whale (Balaenoptera acutorostrata), underwater near Ribbon 10 Reef, Great Barrier Reef, Queensland, Australia, Pacific
Michael Nolan / 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 while others swim to this region to give birth and raise young, Others simply pass through during their annual migrations. The most spectacular and entertaining cetacean of the Great Barrier Reef is the humpbacked whale; lucky visitors can catch glimpses of the five-ton dwarf minke whale and the bottlenose dolphin, which likes to travel in groups.

Dugongs

Dugong
Brandi Mueller / Getty Images

Dugongs, which might be the source of the mermaid myth, are often thought to be closely related to dolphins and whales, but 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, upwards of 50,000 dugongs are believed to be in the vicinity of Australia, an encouraging upturn in numbers for this still-endangered sirenian.