There are four stages of decomposition associated with a whale fall. These stages vary in duration and overlap with one other with the size of the carcass, water depth, and other environmental variables, such as tidal flow. Large, intact whale falls appear to pass through the four decomposition stages, while the stages on smaller or partial carcasses may be truncated. Smaller cetaceans, such as porpoises and dolphins, do not undergo the same ecological succession stages due to their small size and lower lipid content. Researchers believe the presence of Osedax worms may also be a contributing factor in the observed successional differences.