SAN FRANCISCO - A rapt crowd followed a trail of bubbles that zipped over the surface of a seaside pond in the ruins of a 19th century bath in San Francisco.
San Francisco's newest star - the first river otter seen in the city in decades - surfaced its whiskery head furtively, a mouth full of sea grass. The crowd oohed as large waves pounded rocks just offshore, a briny smell and chill in the air.
The otter ducked back under water and took the sea grass underneath a concrete remnant of the historic baths, where the animal was building a nest.
"We came here to see the baths and this was just a bonus," said Eliza Durkin, who brought her son Jonathan to the site for a school project on historic places.
Beyond tourists, the otter has mystified and delighted conservationists, who are piecing together clues to figure out how he got there. The furry creature was first spotted by birdwatchers in September and has since settled into the City by the Bay.
River otters once thrived in the San Francisco Bay area, but development, hunting and environmental pollution in the 19th and 20th centuries has taken its toll on the once thriving local population.
The critters are a living barometer of water quality - if it's bad they cannot thrive. But new populations being seen north and east of San Francisco are giving hope to conservationists that years of environmental regulations and new technologies are making a difference.
"The fact that this otter is in San Francisco and doing so well in other regions of the Bay Area, it's a good message that there's hope for the watershed," said Megan Isadore, director of outreach and education for the River Otter Ecology Project, a group that studies otter populations further north and in the bay.
The group said until now it had no evidence the creatures had returned to San Francisco, and the last sighting was nearly a half-century ago as best they can tell.
The otter is nicknamed "Sutro Sam" after the old baths, which were named after former San Francisco Mayor Adolph Sutro, who built the building which at the time was an engineering marvel.