What organ does a deer lack?

A deer lacks a gallbladder.

The gallbladder is a small digestive organ that stores and concentrates bile made by the liver. Many mammals have one, but true deer, members of the family Cervidae, generally do not. Instead, bile flows from the liver through bile ducts directly into the intestine, where it helps digest fats.

This absence does not prevent deer from processing plant food. Deer are ruminants with a four-chambered stomach, including the rumen, reticulum, omasum, and abomasum. Their main digestive adaptations concern fermenting tough plant material with microorganisms, rather than storing bile in a gallbladder.

The wording can cause confusion because “deer” is sometimes used loosely for animals that are not true deer. Musk deer, for example, belong to a separate family and have a gallbladder. The quiz answer is therefore accurate for ordinary true deer, such as white-tailed deer, mule deer, red deer, and roe deer. Horses, giraffes, and several other mammals also lack this organ.