Between the 1940s and 1970s, manufacturing plants dumped toxic PCBs (polychlorinated biphenyls) into the Hudson River.

Over the last 40 years, cliff swallows have increasingly built their mud nests on concrete highway overpasses.

A population of finches living on an isolated island exhibits natural genetic variation in beak depth.

For decades, trophy hunters have specifically targeted bighorn sheep rams with the largest, most impressive horns.

The Bajau people of Southeast Asia have lived almost exclusively on the ocean for thousands of years, relying on deep free-diving for food.

Snowshoe hares naturally molt from brown summer fur to white winter fur for camouflage.