What primarily causes decomposition odors from animals?

Decomposition odors from animals are primarily caused by proteinaceous materials. When an animal decomposes, the breakdown of its tissues occurs, which includes proteins. The process involves various microorganisms that contribute to the decomposition and the release of gases and volatile compounds as proteins and other organic materials are metabolized. These compounds often have strong, unpleasant odors associated with decay, which is why protein breakdown is a significant contributor to the smells encountered during decomposition.

The other options represent different substances or compounds that do not predominantly lead to the characteristic odors of animal decomposition. Fatty substances can also contribute to odors during decomposition, but they are not the main source. Fragrant compounds can produce pleasant smells, which is the opposite of what one would associate with decomposition odors. Pesticide residues may have their own distinct odors, but they are not a primary factor in the decomposition process itself. Understanding this process helps those in odor control to target the right sources effectively during remediation.