As a hermit crab grows its shell becomes a tighter fit so eventually the crabs need to move into a bigger one, leading to an amazing exchange. Taken from Life Story. Subscribe to BBC Earth: http://www.youtube.com/subscription_center?add_user=BBCEarth BBC Earth YouTube Channel: http://www.youtube.com/BBCEarth BBC Earth Facebook http://www.facebook.com/bbcearth (ex-UK only) BBC Earth Twitter http://www.twitter.com/bbcearth Visit http://www.bbc.com/earth/world for all the latest animal news and