THE ABILITY OF MINIATURE PIGS TO DISCRIMINATE BETWEEN A STRANGER AND THEIR FAMILIAR HANDLER

This study examined the ability of miniature pigs to discriminate betw een a stranger and their accustomed handler. Five 8-week-old Gottingen line miniature pigs were used for two experiments. They interacted da ily with their handler in a pen daily for 5 weeks before and 4 weeks d uring the experiments. During this interaction, the pigs were gently t ouched, talked to in a quiet soft voice, and fed raisins as a reward w henever they approached the handler. They were then trained to receive the reward from the handler in a Y-maze installed in an experimental room. In Experiment 1, each pig was subjected each day to a series of 20 trials. In each trial, the pig was given the opportunity to choose the handler or stranger, who occupied positions assigned at random in each trial at the ends of the two arms of the maze. A choice of the ha ndler in each trial was rewarded with raisins dispensed by the handler . The criterion for successful discrimination was that the pig made at least 15 correct choices in 20 trials (75% correct choice rate: P < 0 .05). All the pigs exceeded the criterion within four sessions and the refore were able to discriminate between the handler and the stranger. However, two pigs exhibited stimulus generalization toward the experi menters in the early sessions. In Experiment 2, the voice, odor and si ght of the handler and the stranger were obscured in various combinati ons. The seven treatments were nonobstruction of visual (V), auditory (A), olfactory (O), visual and auditory (VA), visual and olfactory (VO ), auditory and olfactory (AO) and obstructions of all (NO) cues, resp ectively. There were no pigs which achieved successful discrimination in all the treatments, and there were individual variations in their p erformance. In conclusion, the pigs could discriminate between a stran ger and their familiar handler with all three cues, but obstruction of visual, auditory and/or olfactory cues affected their discrimination. It seems that olfactory cues alone were of little importance. (C) 199 8 Elsevier Science B.V.