Aggression and group size in domesticated pigs, Sus scrofa: ‘when the winner takes it all and the loser is standing small’

JOURNAL:  Animal Behaviour
AUTHORS: I.L.Andersen, E.Nævdal, M.Bakken, K.E.Bøe
SUMMARY: We developed a theoretical model that describes how aggression among unacquainted pigs is a function of group size. As the number of potential competitors increases, more individuals will benefit from not getting involved in costly fights. To verify predictions from this model, we compared aggression among unacquainted, weaned pigs in three group sizes (6, 12 and 24 pigs). There were significantly more fights per individual in groups of six and 12 pigs than in groups of 24 pigs, and the proportion of pigs not participating in fights was significantly higher in the largest group. We conclude that pigs are able to alter their behaviour according to how the actual competitive situation changes with group size.
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CULTURAL REFERENCE:  "The Winner Takes It All" is a song recorded by the Swedish pop group ABBA. It is a ballad in the key of F-sharp major, reflecting the end of a romance. 

Scientific paper

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