A fecal plug is the hardened mass that forms in an American black bear’s colon during hibernation.
While denning, the bear’s metabolism and digestive activity slow dramatically. It normally does not eat, drink, urinate, or defecate for months, so material remaining in the intestine gradually loses fluid as the intestinal walls absorb it. The result is a dense, hardened mass known as a fecal plug, also called a tappen.
The plug can contain undigested food, shed intestinal cells, bedding material, and small particles such as soil or rocks. Dried pieces of callused skin from the bear’s footpads may also contribute, because bears sometimes lick or chew their feet during late hibernation.
A common misconception is that bears deliberately eat large quantities of indigestible vegetation to create the plug. The mass forms mainly because intestinal contents remain in place during prolonged fasting and dehydration. After emerging in spring, the bear expels it, often near the den entrance.