Krieger J, Grandy R, Drew MM, Erland S, Stensmyr MC, Harzsch S, & Hansson BS (2012). Giant Robber Crabs Monitored from Space: GPS-Based Telemetric Studies on Christmas Island (Indian Ocean). PloS one, 7 (11) PMID: 23166774

Anybody who knows me will tell you that I have a soft spot in my heart for the hard shell of our fellow crab-man. For all the land-lubbers out there, the crab is a heavily-armored, sideways-running little fellow that specializes in shoveling detritus (= trash) into its adorable little mouth with an often over-sized claw appendage. To me, the main appeal of the crab is its dignified air of feistiness. Unlike most softy animals, crabs do not like to be handled, and if you pick them up they will pinch you with all the hatred they can muster. Crabs also have beautiful brains and, as we shall see, possess a unique brand of crusty intelligence.

There are all sorts of freaky crabs out there, but the most inspiring is the absurdly proportioned giant robber crab that resides on Christmas Island in the South Pacific. These friggin crabs can weigh about 10 lbs, they climb trees, and they rip apart coconuts and devour them like their mike’s and ike’s (sic). This cushy crab lifestyle allows them to live to the ripe age of 60. Some folks in the recently prolific Hansson Lab at the Max Planck Institute for Chemical Ecology somehow convinced somebody to let them go to Christmas Island and study the navigational abilities of giant robber crabs. Their experimental protocol went as follows:

  1. Snatch a robber crab
  2. Glue a GPS tracking device to its carapace
  3. Sit back and watch where it goes via satellite transmission
  4. Snatch the crab again, put in a trash bag, transport it across the island, and release it
  5. See if the crab can get back home

This pape clearly demonstrates that robber crabs live a rambling lifestyle. After spending a few days or weeks in one area, a crab will get the itch to roam, and will pick up and haul his barnacled ass from the inland rainforest to the seashore. After a spell at the shore, he’ll pack up and hitch back into the rainforest. Over time, robber crabs learn preferred routes that they repeatedly traverse throughout their long lives. Most remarkably, if you put a crab in a trash bag and haul it a mile away, it will almost immediately return to the spot where you snatched it.

Aside from the obvious conclusion that robber crabs are dynamic, intelligent beasts, this pape also establishes the robber crab as an important model system for studying what it means to live a deeply fulfilling life. 

Contributed by butthill


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