Sea lions suddenly abandon Pier 39

[Ericpittenger]

After maintaining a constant presence for many years, all of the sea lions have mysteriously left Pier 39 in San Francisco.  Scientists are baffled - it's unknown where they went or why.
 
http://news.yahoo.com/video/sanfranciscocbs5-15751300/sea-lions-mysteriously-disappear-from-pier-39-17346489
 
In this news video, it's said that during summer, many of the sea lions head south to mate, while some always stay behind.  But in winter they congregate at Pier 39.  A month ago they were there in record numbers, now they're suddenly gone.
 
IMHO, when animals suddenly leave an area, it's usually because they sense some impending danger.

[Yowbarb]

That's scary when animals have a mass exodus -
I wouldn't want to be living there now.
Yowbarb

[Carlg]

I read somewhere that there was a large school of sardines or anchovies and that these are favorite foods of sea lions.  So let