A note on visual, olfactory and spatial cue use in foraging behavior of pigs: indirectly assessing cognitive abilities

Abstract

The micro pig’s ( Sus scrofa) ability to use visual, olfactory and spatial cues to locate a food resource in a novel environment was investigated. In Experiment 1, four castrated male pigs were trained to identify a food resource—one of two plastic flower-pots placed within a 12.8 m×6.7 m arena. Correct pots differed only in color from incorrect pots. During the first 10 trials, the location of the correct pot was constant, and pigs were allowed to search until the correct pot was displaced. Pigs were then presented 10 single-choice trials with constant location, repeated until each pig made 8 of 10 correct choices. Next, pigs were given 10 single-choice trials with location of correct pot randomized, to determine whether they would follow visual cues (color) or return to previously correct locations (i.e. rely on learned spatial cues). Trials were then conducted with 4, 6, 8 and 10 pots. In random location trials, pigs performed above chance ( P<0.005). Experiment 2 was designed to assess performance with olfactory cues. Discriminative stimuli were food extract odors. Pigs were required to select pots containing a specific odor. Trials used 2, 4, 6, 8 or 10 pots. In all, except two-pot trials, pigs performed above chance on random location trials ( P<0.005). We propose that when multiple cues are available, pigs can use vision and olfaction to navigate, rather than relying solely on spatial memory.