Waste derived from human activitirs, such as rapeseed placentiform from the extraction of rape oil;fruit faeces from the extraction of fruit juice;chicken excrement from the scall farming of chickens.
And further detective work, including examination of the mice's faeces, revealed higher levels of a strain of Clostridium called OUT-1105 in the fat mice than in the thin ones.
One popular theory is that the wolves which became dogs acted as rubbish-disposal agents for groups of people, by eating their waste, possibly including their faeces.
Most people infected with V. cholerae do not develop any symptoms, although the bacteria are present in their faeces for 1-10 days after infection and are shed back into the environment, potentially infecting other people.
Based on an analysis of the faeces of both vegetarians and meat eaters, Dr Hazen suspects bacteria of several genera, including Clostridium and Fusibacterium.
Geese and other waterfowl do, nevertheless, seem to form a significant part of polar bears' diets, for studies done in the 1960s found a lot of bird remains in the animals' faeces.
They are a threat to the environment because they do not easily biodegrade, and recent research has found them in dust, food, fruit, bottled water and, as a result, animal and human faeces.