Elkhorn Slough Seal & Kayak

A harbor seal glides up to the bow of a kayak in Elkhorn Slough, the tidal estuary that cuts inland from Moss Landing on Monterey Bay. Its spotted head and whiskered face are turned squarely toward the red hull, body trailing behind in the flat gray water, with wisps of green eelgrass drifting on the surface around it. Harbor seals here are famously curious about boats, often surfacing within a paddle's length before slipping under again.

That spotted coat is worth a second look. The pattern is unique to each animal and stable across years, which makes a face like this one identifiable. A neural network trained on 1,752 photographs of 408 seals picked out individuals correctly on its first guess 88 percent of the time, and later work using a catalogue of 672 seals traced the same animals returning to the same haul-out sites year after year. The seal approaching this kayak has a home mudbank somewhere in the estuary, and in principle a name in a database.