Many San Franciscans are drawn to the outer limits of human experience, and others are just born on the greener side of that fence :)
In addition a huge number of pets, the city hosts a flock of wild parrots (Parrots of Telegraph Hill), a herd of buffalo in Golden Gate park. California Gray Whales swim down and up the coast in their annual Alaska <-> Mexico commute. The bay itself is home to many seals, sea lions, gulls and other creatures.
Golden Gate Park, Fort Funston, Crissy Field, and Dolores Park are very popular dog spots - although there are *many* others.