These days its rare to find humans living far from other animals, even those that spend a large portion of their lives in the sea.  Sometimes, like with the Galapagos sea lions on San Cristobal island, they are very close neighbours.  

So far the sea lions seem fairly happy with their two-legged neighbours, but bubbling beneath the relationship is something more insidious.  

Disease.

A study by Dr Paddy Brock of the Zoological Society of London has shown that the sea lions in the bustling island of San Cristobal are more likely to have reduced immunity and body condition than their counterparts on the rat/mice/dog/cat/human free island of Santa Fe.  

This reduction is a problem because the "sea lions [in San Cristobal] come into close contact with domestic animals, where the bay in which the sea lions live is home to more than two hundred vessels and is contaminated with faecal coliform bacteria by sewage from the town water system".