Probably started when old cargo ships were swarmed with rats eating the supplies and spreading diseases. I have read about several people sailing around the wo

Probably started when old cargo ships were swarmed with rats eating the supplies and spreading diseases. I have read about several people sailing around the world though that have kept cats aboard in more recent times. Robin Lee Graham (http://en.wikipedia.org/wiki/Robin_Lee_Graham http://en.wikipedia.org/wiki/Robin_Lee_Graham) had several during his voyages, his book Dove is excellent by the way for anyone interested in sailing and exploration.