Pigs adjust their foraging preference depending on who they are foraging with
We investigated whether pigs can learn to deceive an exploiting dominant in a competitive foraging task. Subordinate pigs were trained to forage for two differently-sized food baits hidden in two of 12 buckets in an arena. The first arena visit was a 'search visit' to locate both baits. The second visit was for 'relocation' with the same two buckets baited. Repeated search and relocation visits turned subjects into informed foragers (I-pigs) that knew in relocation visits where the baits were. One of the I-pigs' heavier pen-mates was turned into a non-informed forager ('NI-pig'): she always received only one bait, in a different location each visit. Another heavy pen-mate returned to the same baited bucket each visit (non-follower, 'NF-pig'). After training, seven I-pigs were paired with either their NI or NF-mate during relocation visits ('I-NI tests', 'I-NF tests'), or tested alone ('I-alone tests'). I-pigs completed 48-72 I-NI tests, 15 I-NF and 20 I-alone tests. Replicated-Goodness-of-Fit Tests revealed a preference for retrieving the large bait first in I-NF and I-alone, but not in I-NI tests (I-NF:Gpooled=5.81, df=1, p<0.05; I-alone:Gpooled=6.49, df=1, p<0.05; I-NI:Gpooled=0.63, df=1, p>0.01). I-pigs, then, lost their bias for retrieving the large bait first when with their exploiters, but did not clearly switch to first retrieving the small one as predicted. A possible explanation is that, against expectation, retrieving the small bait first in I-NI tests led to a foraging advantage in only two I-pigs (measured as the combined time each I-pig spent at the two baited buckets; analysis across pigs by GLM with the following factors: pig (df=6, F=1.77, p>0.05), bait located first (df=1, F=0.58, p>0.05), pig*bait located first (df=6, F=2.92, p<0.01)). In conclusion, pigs adjusted their foraging strategy to who they foraged with, but did not learn to deceive possibly because no advantage was gained from so doing.