Beachcombing

Sail to the Galapagos Islands, where Charles Darwin made his most famous discoveries, and you'll likely be met on the lava rocks near the water's edge by two stalwart creatures: the marine iguana and the sally lightfoot crab. Both species use their pointed claws not to hunt but to keep hold of the craggy shore. The crabs usually scavenge for leftovers, and the iguanas dive into the cold, current-prone Pacific for seaweed.

Photographer Tui De Roy caught the sally lightfoot pictured here as it gleaned a snack by picking dead skin off the iguana's head. Having come ashore to warm up after grazing, the reptile seemed unfazed, even pleased, by the exfoliation treatment. And the crab, no doubt, enjoyed its well-salted meal: marine iguanas expunge their excess salt in a spray of nasal rheum that often ends up encrusting their spiky crowns.

De Roy encountered the pair on Espanola, the oldest and most southerly island in the Galapagos. In true Darwinian form, the marine iguanas on Espanola are far more colorful than the same species on other islands in the chain. Recent studies have shown that these iguanas have an unusual adaptive trait: their skeletons can shrink when times are tough and regrow in times of plenty. Darwin, who described them as "disgusting" and "clumsy," may have been too dismissive when he clambered onto their turf.

Photograph by Tui De Roy

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