For the BBC Two series 'Wonders of the Monsoon' the team recorded extraordinary new behaviour of the worlds largest crab - the robber crab, hunting amongst the millions of migrating land crabs on Christmas island, 2000 kms of the west coast of Australia. Although the significance of this footage seems to have been overlooked, it does reveal for the first time that the robber crab, believed to be mostly vegetarian, also has a taste for meat.
Robber crabs powerful pincers that are adapted for opening coconuts, and they have been observed feeding on carrion, but the new footage reveals robber crabs actively predating by pouncing, and using their pincers to puncture the red crabs shell before opening it up to eat the soft parts.
Robber crab sizing up a smaller Christmas Island crab
The moment of attack
Robber crab punctures the shell of the Christmas Island crab before tearing it apart to eat
The Christmas Island crab migration is triggered by the monsoon rains. 45 million red crabs migrate en masse from the forest to the sea to spawn. It’s a flowing river of glistening red crabs - one of the worlds most amazing natural spectacles.
Christmas Island crab photobomb
It may be that the robber crabs hunting streak is tuned into this seasonal migration. This is when the christmas island crabs are loaded with nutrient rich eggs stored in their bodies. Feasting on this rich food may be a huge boost for the robber crabs in preparation for developing their own spawn. It was a lucky find for the crew when they eventually found a scene of carnage, and the robber crabs waiting in ambush.