Why did the sea lions on Pier 39 disappear?

Last week, just as in December 2009, the sea lions were out lazing in the sun and posing for photos one day - and then, without notice, they disappeared. On one hand, it's not unusual for the sea lions around Fisherman's Wharf to leave their docks, particularly at this time of year, said marine scientists. [. read more

Sea lions are migratory mammals, and tend to migrate to other places to breed. They usually migrate from Pier 39 in July to Channel Islands, and then return in August. read more

After going missing for several weeks, the famed sea lions that make their home on San Francisco’s Pier 39 have returned. read more

Sea lions are migratory mammals, and tend to migrate to other places to breed. They usually migrate from Pier 39 in July to Channel Islands, and then return in August. Everyone was confounded when they disappeared in Dec 2009 but they returned in a few months. So don't worry - they will be back. read more

At one point San Francisco's Pier 39 was home to more than 1,700 sea lions, but overnight the mammals have all slipped off. read more