Tourists flock to Fisherman's Wharf each year for the seafood, the wax museum and the stunning views of San Francisco Bay. But for many, the stars of the show are the California sea lions, the flippered and seemingly friendly fish-eaters that lounge and play by the water's edge.
Now, a series of human-sea lion confrontations has officials rethinking their relationship with the area's most visible wildlife attraction. And experts say sea lions are not as cute and cuddly as they seem.
In the most frightening of the recent episodes, a single rogue sea lion bit 14 swimmers this month and chased 10 more out of the water at San Francisco's Aquatic Park, a sheltered lagoon that adjoins the bay.
Some scientists theorized the animal's unusually aggressive behavior resulted from being poisoned after eating fish contaminated by a toxic algae bloom. But wildlife experts say even healthy sea lions are best left alone.
In Southern California in June, a sea lion charged several people on Manhattan Beach, then bit a man before swimming away. And in Berkeley, a woman was hospitalized in the spring after a sea lion took a chunk out of her leg.
Last year, a group of sea lions took over a Newport Beach marina and sunk a vintage 15m yacht. And a lifeguard in Santa Barbara was bitten three times while swimming off El Capitan State Beach.
Sea lions, which can reach 450kg, will typically bite only if they feel threatened or cornered. And they are more likely to flee people than fight them if they can find an escape route. Researchers have described the most recent attacks, where some swimmers were chased through open water, as abnormal behavior.
Still, with a population numbering about 200,000 and growing, the seals and their onshore human neighbors are increasingly likely to meet. And the encounters will not always be friendly.
Sea lions accustomed to the easy pickings of seafood scraps in popular fishing areas can become aggressive toward people if they fear that food source could disappear -- a likely factor in the Berkeley attack, said Jim Oswald, a spokesman for the Marine Mammal Center just across the Golden Gate Bridge from San Francisco.
A food shortage off the Southern California coast could be driving more hungry sea lions than usual to San Francisco Bay, said Lynn Cullivan, a spokesman for San Francisco Maritime National Historical Park.
Humans could also be exacerbating aggression in sea lions in a more damaging way.
Toxic ocean algae blooms fed by agricultural runoff and other pollution can lead to the poisoning of marine mammals by a chemical called domoic acid, which is known to cause brain damage. The Marine Mammal Center, which describes itself as the largest rehabilitation center of its kind in the world, treated more than 200 sea lions for domoic acid poisoning last year.
Veterinarians at the center believe the brain damage caused by the poison could have led to the marauding animal's erratic behavior in Aquatic Park, Oswald said, though they cannot be sure without examining the animal directly.