The systematic collection of scientific data that enables a wildlife impact assessment is an essential part of an oiled wildlife response.An oil spill that happens in or near the areas where marine wildlife is concentrated is likely to affect a considerable number of animals. It is important to be able to tell how many animals, or which proportion of a population may have been killed by the pollution. A reliable scientific assessment can only be made if the right data have been systematically collected since the very beginning of the event. This includes the systematic and frequent monitoring of beaches and other parts of the coast line to look for carcasses or live animals that have washed ashore, and carrying out at sea experiments (drift block experiments that mimic the behaviour of the carcass of an animal that dies at sea), to assess the proportion of all impacted animals that die at sea and therefore will not be collected on a beach.A wildlife impact assessment should include a scientific analysis of the carcasses that have been collected. Total numbers, numbers per species, age distribution per species and, if possible, biometric analysis to determine proportional impact per geographic sub populations are all important data that can be produced if activities are carried out according to standard protocols.