Luangwa River, Zambia, July 20, 2008—Open wide! Hippos fight in a watering hole along the Luangwa River—home to the world's largest population of the low-slung, big-bellied plant-eaters.

Hippos—which are listed as vulnerable by the International Union for the Conservation of Nature—rely on fresh water for their survival. This puts them in tightening competition with humans, who need the water to irrigate crops.

The Wildlife Conservation Society recently launched a project to train wildlife poachers in alternative activities, from carpentry to beekeeping, in hopes of reducing hippo-human conflicts.