03/08/2013 10:01 pm ET Updated May 08, 2013

'Sutro Sam,' San Francisco River Otter, Finds A New Home (PHOTOS)

An adorable river otter who had been making his home in the water by San Francisco's Sutro Bath ruins since last fall finally decided it's time to move on -- much to the chagrin of his doting fans.

The sweet-faced sea creature, nicknamed "Sutro Sam," has captivated sightseers and stunned scientists, who claim he's the first river otter to appear in San Francisco in decades.

Conservationists remain uncertain as to why Sam wound up in the big city. While the species once thrived here, development and pollution rendered them virtually nonexistent, and according to the River Otter Ecology Project, the last sighting before Sam occurred nearly a half-century ago.

"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," Megan Isadore, the project's director of outreach and education, told The Associated Press.

Isadore said Sam may have migrated to San Francisco from Marin County, where her organization has been studying another group of river otters.

And where he's wandered off to also remains a mystery. Isadore told the San Francisco Examiner that he hasn't been spotted since February 23, and since it's the beginning mating season, he may have left in search of a female companion.

“He moved on because of a lack of food or because his hormones were kicking in," she said to the San Francisco Chronicle. “I think people will miss him, but it is wonderful that he was there and that a lot of people in San Francisco got to see him."

Sam might have swum back to join his counterparts up in Marin. Or, as SFist points out, he probably just moved to Oakland with everybody else.

Take a look at some photos of Sutro Sam below:

Sutro Sam