Once, at the National Zoo in Washington, D.C., I watched an orangutan vomit on the glass wall of its enclosure. I was standing next to a group of schoolchildren, and they laughed in response. Then the primate stuck out its tongue, pressed it to the glass, and dragged it through the vomit. The children screamed. We moved to the next exhibit, where this same group and I watched a gorilla stick its finger first into its anus, and then into its mouth. As one can probably guess, the schoolkids went berserk.

This happened a few years ago, but it wasn’t until I recently attended a meeting on zoo animal obesity that I learned these separate-but-equally-unappealing behaviors have scientific names: regurgitation and reingestion, and coprophagy, respectively. The conference was the Crissey Zoological Nutrition Symposium, held at North Carolina State… More…