These crabs are BIG!
VulcanSpirit
Richard & Alison Brunstrom
Fri 31 Aug 2012 18:25
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One of the special animals here on Niue is the
coconut crab, Birgus latro, known locally as uga (pronounced ungah).
These are the biggest land arthropods alive in the world today, and approach the
maximum theoretical size for a land animal with an exoskeleton - over 4kg, with
a spread across their legs of nearly 1m! They are just about the only animal
other than a human that can open a coconut, and we're told by the Niueans that a
big adult can sever your finger if you unwisely let one get into its claws. Here
is one (rather a small one!) feeding on a coconut bait (the locals 'hunt' them
to eat). The crabs are adult at 5-6 years and take 50-60 years to reach full
size, moulting every twelve months.
 Their life cycle is unusual. The adults have a
lung, and will drown in water, but they lay their eggs in the sea at high tides
in November. The eggs hatch immediately and go through several larval stages in
the sea over a few months, eventually metamorphosing into baby marine crabs -
hermit crabs. After a while the small crabs leave the water for ever and become
air-breathing. As they grow they quickly become too big for a shell and dump it.
Their soft body hardens (with chitin & chalk) and they assume their adult
shape.
Coconut crabs have a very well developed sense of
smell, and hunt nocturnally for fruit, coconuts and carrion. They are trapped
using opened coconuts (just a small slit that they can get a claw into, but too
small for a rat to enter) hung on rocks or on trees. Surprisingly the crabs
freeze when illuminated at night, and are thus very easy to catch - in the
daytime if disturbed on the surfae they scurry away very quickly indeed into a
rock crevice or burrow.
Lovely creatures.
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