Consider a typical garden somewhere in Ireland – or, for that matter, in Britain, France or Massachusetts. Regardless of its exact size, many animals will die there on a daily basis. Most will leave no trace of their existence; within a few days or weeks it will be as if they had never lived. Far from becoming fossils for palaeontologists of the distant future to inspect and interpret, they will leave no clues as to their structure, function, or ecological context.
A good example is the death of an earthworm when a blackbird pecks it out of the top layer of the soil and eats it whole. Not only will the worm’s flesh be completely digested in the alimentary canal of the bird, but earthworms have no hard parts – no teeth, shell or bones – to be egested by the bird and left on the ground for possible fossilization.