On Thursday at noon, I ditch the San Francisco courthouse where I work as a Spanish interpreter and high-tail it home to swap my conservative suit for breeches and dusty paddock boots. I arm myself with allergy pills, nasal spray and a puff from an asthma inhaler. Patches on my windbreaker and baseball cap identify me as a National Park Service volunteer.
I take the Golden Gate Bridge out of the city. Just across the bridge await the Marin Headlands, a swooping series of promontories and wind-swept hills fronting the Pacific. Only a few minutes from the booming city, this wild space is home to bobcats, coyotes, red-tailed hawks, herons, rabbits, snakes and the occasional mountain lion. A mile down a fire road stands the corrugated-metal barn that houses the four horses of the Mounted Patrol.