A young margay cat peeks over a step at the Smithsonian Tropical Research Institute station on Barro Colorado, a forested island in the Panama Canal waterway. The island rises from Lake Gatun, which formed in 1907 when the Chagres River was dammed during construction of the canal.

(Text adapted from and photograph shot on assignment for, but not published in, "The Panama Canal Today," February 1978, National Geographic magazine)