Hundreds of
crown-of-thorns starfish found on a beach in southern Japan in January
stranded themselves because they were starving, say researchers.
More than 800 were discovered on a 300m stretch of sand on
Ishigaki island.
The starfish population "outbreak" was first identified in
2009, when masses of juveniles were seen feeding on the island's outer
coral reef.
The coral-eating starfish then took three years to move onto
the beach where they perished.
The reason for the starfish
population boom is not clear, but the strange behaviour has shown marine
scientists what can happen when these slow-moving creatures completely
deplete their food source.
"The shortage of food, corals, is a probable cause of the
stranding," said Go Suzuki from the Fisheries Research Agency, who
witnessed the phenomenon from his research station.
In a paper, published
in the journal Coral Reefs, Mr Suzuki and colleagues described how
an area once covered with up to 60% coral was reduced to 1% by the
voracious starfish.
The marine scientists described how the starfish gradually
moved closer to the beach, possibly in search of more coral to feed on.
Mr Suzuki suggested that the current may have helped the
starfish along their doomed path, pushing the animals towards the shore.
Noting that they died on the beach, rather than in the water,
the team concluded that when the starving starfish were eventually
washed up they were too weak to return to the sea.
source : http://www.bbc.co.uk/nature/18294729
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