Crown-of-thorns starfish stay up all night to overindulge

In a new study, researchers have observed that crown-of-thorns starfish can actually find their way home after a long night of feasting on corals. The research suggests that healthy tropical reefs with an abundance of Acropora corals encourage the overindulgent behavior of crown-of-thorns starfish. 

The study is the first of its kind to show that  crown-of-thorns starfish have the ability to find their way home, but only when their surrounding community is well-stocked with corals. 

The experts documented this behavior on the Great Barrier Reef, where the starfish were seen emerging from their shelters in the afternoon, feeding on coral throughout the night, and returning home at dawn.

Study lead author Dr. Scott Ling is a senior lecturer at the Institute for Marine and Antarctic Studies at the University of Tasmania.

“The crown-of-thorns starfish often partied all night, slept-in and only those with a well-stocked larder found their way home – so it’s very much a teenager model of behavior,” said Dr. Ling.

“Their preferred prey is Acropora corals,” said study co-author Professor Morgan Pratchett from the ARC Centre of Excellence for Coral Reef Studies. “When populations of Acropora dropped, the starfish didn’t return home. Their behavior is directly linked to the local abundance of Acropora.”

Acropora corals have served as an important reef-building species for the past two million years. These fast-growing corals are the building blocks of reefs across the world.

The study findings indicate that healthy reefs with a high cover of Acropora corals are the target of crown-of-thorns aggregations and outbreaks. The starfish are known for preying on large swaths of coral reefs, and these outbreaks have caused widespread and sustained coral loss throughout the Indo-Pacific region.

Using time-lapse photography, the researchers tracked the movements of 58 starfish in the northern and southern Great Barrier Reef during an outbreak in 2015. When Acropora corals were unavailable, the starfish were typically homeless and roamed up to 20 meters per day.

“Unlike sea urchins that can switch diet once they overgraze kelp forests, results of the time-lapse monitoring indicate that the starfish will consume available Acropora and ultimately eat themselves out of house and home before dispersing in search of new feeding grounds,” said Dr. Ling.

Previous crown-of-thorns outbreaks were documented on the Great Barrier Reef in 1962, 1979, 1993, and 2009. The combined threat of mass-bleaching and crown-of-thorns outbreaks could have catastrophic consequences for coral reefs.

“By better understanding the behavior of these starfish we can help prevent and control their outbreaks, which will help alleviate the pressures on coral reefs,” said Professor Pratchett.

The study is published in the journal Proceedings of the Royal Society B

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By Chrissy Sexton, Earth.com Staff Writer