Crown-of-thorns starfish

Crown-of-thorns starfish (COTS for short) feed on coral. These spiky marine creatures occur naturally on reefs in the Indo Pacific region, including the Great Barrier Reef.

Crown-of-thorns starfish

In normal numbers on healthy coral reefs, COTS are an important part of the ecosystem. They tend to eat the faster growing corals which gives the slower growing species a chance to catch up, enhancing the coral diversity of our reefs.

However, when the coral-eating starfish appear in outbreak proportions, the impact on coral reefs can be disastrous.

A 2012 study by the Australian Institute of Marine Science revealed that crown-of-thorns starfish and tropical cyclones were the two leading causes of coral cover loss on the Great Barrier Reef over the previous 27 years.


Acanthaster solaris (Scientific name)

Nocturnal by nature, they can move at speeds of up to 20 metres an hour.


COTS prey on nearly all corals, and can eat their way through 10 square metres of it a year.

The COTS spikes or spines contain toxins that are poisonous to both humans and marine creatures.

It’s the world’s second largest starfish, reaching up to 1m!


They eat their coral prey by extruding their stomachs out from their bodies, covering the corals.

Like most starfish, if it loses one of its arms, a COTS can regrow a new one in around six months.

An adult Crown of Thorns Starfish can live up to 9 months without eating!

If 15 Crown of Thorns Starfish are found in a one hectare area, it’s called an outbreak.

Natural predators include the giant triton snail, titan trigger fish, starry pufferfish, humphead maori wrasse, yellow margin trigger fish, harlequin shrimp and lined worm.

Factors that influence outbreaks of COTS include excess nutrients from run-off in the ocean and overfishing or removal of the natural predators of COTS.

#What we're doing

COTS Control

COTS Control

Controlling COTS numbers through the Reef Trust Partnership.