Plastic trap takes heavy toll as crabs seek shelter Australia
A study published in May told of a harrowing trip to Australia’s Cocos (Keeling) Islands two years before, when researchers recalled seeing beaches that were ‘‘drowning in plastic’’ – an estimated 414 million pieces of it.
But Jennifer Lavers and her research team now say they made another startling observation while digging through copious amounts of litter on that 2017 trip.
Many of the bottles, cans and containers were not empty. Scores of hermit crabs, mostly dead, were trapped inside.
The scientists say plastic debris has caused the deaths of more than half a million hermit crabs on the Cocos Islands and the similarly remote Henderson Island in the South Pacific.
‘‘The question was, is Cocos unique, or is this a more widespread problem that could be happening anywhere?’’ said Lavers, a researcher with the University of Tasmania’s Institute for Marine and Antarctic Studies.
The researchers estimate that 570,000 crabs have been killed on the Cocos Islands, which comprise 27 islands, and another 61,000 on Henderson Island.
Hermit crabs are not born with a shell, and spend much of their lives seeking one that needs to be replaced as they grow. When a crab dies, it emits a chemical signal to let others know that a potential shell has become available.
A hermit crab that dies after trying to make a home out of plastic sets off an insidious chain reaction – the smell attracts another that dies, and so on, generating an ultra-strong signal that leads even more of the crabs to an almost-certain demise.
It is unclear how the losses have affected the overall hermit crab population.
Previous reports suggested that the hermit crab population on the Cocos Islands was declining, Lavers said, potentially compromising a marine ecosystem that relies on the crabs to fertilise soil, disperse seeds and eat detritus.