Crabs uses various
methods to migrate from their homes to other places and
back.
Local topography is a
visible cue which uses polarised light patterns formed due to light
scattering by air borne particles.
The polarised light
patterns shifts in the sky depending on the suns position shifts
,which makes the crabs and other animals find their way
home.
Even they use the
position of the stars during night based on the rotation of the sky
about a fixed point like pole star.
Crabs also sophisticated
math for navigation by calculating the number of strides and the
distance between each stide from home .ie they sum up the
strides.This is done by using a sensor called proprioreceptorson
their legs .