Ability of the pig to distinguish between conspecific urine samples using olfaction

In two female pigs it has been shown using operant conditioning techniques in which the animals pushed panels with their snouts in order to obtain food, that they could distinguish between the oder from urine samples taken from other pigs. In the discrimination task, the pigs faced two panels and a tube adjacent to one of the panels emitted urine odor used as the positive discriminative stimulus while another tube adjacent to the other panel emitted the negative discriminative stimulus consisting of odor from another urine sample. Only presses on the panel associated with the positive stimulus were reinforced on a fixed ratio schedule of 6. Both positive and negative discrimination stimuli were presented simultaneously. After each reinforcement the position of the positive and negative odor stimuli was varied according to the Gellerman series. When fully trained, the pigs made very few responses on the incorrect panel.