The calls of Orca whales in the Pacific are getting longer, so they can be heard by other whales over the noise of heavy boat traffic. Orcas only do this when engine noise reaches a critical level.
Paul Rincon writes in bbcnews.com that ironically, much of the boat noise that bothers them comes from whale-watching tourists. No difference was found in the length of their calls over the 1977-81 and 1989-92 period, but there was a 10-15% increase in the length of calls made by the Orcas during the 2001-03 period. Their numbers have dropped, so they also have to make their calls longer in order to reach each other. Background noise could eventually be the end of them, since they need to communicate and cooperate in order to find food.