When a pig is trapped in a separate enclosure from its group, other pigs come to its aid, suggesting they may have empathy for each other.
Researchers have previously found that domestic pigs (Sus scrofa domesticus) become stressed when they see others of their kind in a fearful state. at the Research Institute for Farm Animal Biology in Dummerstorf, Germany, and her colleagues wanted to test whether the animals would take action to relieve each other’s distress.
They placed groups of nine or 10 pigs in a pen connected to two smaller compartments. Each compartment was separated from the main pen by a door next to a window. Each door had a latch that could only be opened from the main pen.
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The pigs freely learned to open the doors by using their snouts to nudge the door handles. Then the researchers trapped one pig inside one of the two compartments, while leaving the other compartment empty.
Out of 75 trials, each lasting 20 minutes and with different trapped pigs, a group member in the main pen released the confined hog 85 per cent of the time. On average, it took the pigs 2.2 minutes to open the door leading to the trapped animal. They also opened the door to the empty compartment in 68 per cent of the trials, but less quickly, taking 3.9 minutes on average.
Pigs that showed signs of distress when they were trapped – by screaming, squealing or attempting to escape – were 2.4 times more likely to be rescued and were helped sooner by their pen-mates compared with those that didn’t give such signals.
While the findings suggest that pigs feel empathy for each other, it can’t be ruled out that they were acting selfishly and simply enjoyed solving the puzzle, says at the Swiss Federal Institute of Technology in Zurich, who wasn’t involved in the study.
If they really do help each other based on empathy, this could affect how we perceive pigs and the consumer choices we make, says Goumon.
bioRxiv
