Effect of increased floor space on aggressive behaviour in male turkeys ( Meleagris gallopavo)

Abstract

Under commercial rearing conditions, domestic turkeys are often aggressive towards “pen-mates”, and this may lead to serious injuries or even death. We hypothesized that restricted space, as a consequence of high stocking density, might prevent the attacked bird from retreating from its opponent to avoid serious consequences from an encounter. This study examines the aggressive response in 10 groups of five familiar turkey toms, comparing behaviour to an unfamiliar conspecific that is introduced to two pens of different sizes. Groups were tested both in a small (2 m × 3 m) and in a large (6 m × 13 m) pen for 30 min. Aggressive interactions and distances between the newly introduced bird and test-group members, and additionally distances among test-group members, were recorded. In the small pen we observed significantly more aggressive pecks and threats to the introduced bird. In the large pen introduced birds kept a greater distance from the group than in the small pen. However, they did not make use of all of the available floor space in the large pen. The mean number of fights and chases per test was no different between the two pens. We conclude that the aggressive response of the group was reduced with an increase in floor space. To summarise, the present study shows that in small groups of turkeys, an increase in floor space reduces the number of aggressive pecks and threats aimed at an introduced unfamiliar conspecific. Additionally, we found evidence that there might be a critical distance below which retreating from an opponent is not successful in avoiding aggressive encounters.