A small animal, such as a mouse, smells for about a week after death. A larger animal, such as a raccoon, smells bad for more than a month after death. The smell remains until the body completely decomposes down to dry bones.
The process of decomposition after death begins with intestinal bacteria starting to break down the internal organs. Insects lay eggs on the body, and maggots begin to feed, often as soon as 24 hours after death. After about three days, the body begins to bloat and emit fluids and foul-smelling gases. Maggots consume the bulk of the body during the next few days or weeks. The body continues to emit a strong odor during this phase of decomposition. Eventually, only bones, cartilage and dry skin are left behind.