Pattern of Social Interactions after Group Integration: A Possibility to Keep Stallions in Group

Abstract

Horses are often kept in individual stables, rather than in outdoor groups, despite such housing system fulfilling many of their welfare needs, such as the access to social partners. Keeping domestic stallions in outdoor groups would mimic bachelor bands that are found in the wild. Unfortunately, the high level of aggression that unfamiliar stallions display when they first encounter each other discourages owners from keeping them in groups. However, this level of aggression is likely to be particularly important only during group integration, when the dominance hierarchy is being established, whereas relatively low aggression rates have been observed among stable feral bachelor bands. We investigated the possibility of housing breeding stallions owned by the Swiss National Stud in groups on a large pasture (5 stallions in 2009 and 8 stallions in 2010). We studied the pattern of agonistic, ritual and affiliative interactions after group integration (17–23 days), and the factors influencing these interactions (time after group integration, dominance rank, age or experience of group housing). We found that stallions displayed generally more ritual than agonistic and than affiliative interactions. The frequency of agonistic and ritual interactions decreased quickly within the first three to four days. The frequency of affiliative interactions increased slowly with time before decreasing after 9–14 days. A stable hierarchy could be measured after 2–3 months. The highest-ranking males had less ritual interactions than the lowest-ranking. Males had also less agonistic, ritual and affiliative interactions if they had already been housed in a group the previous year. Therefore, we found that breeding stallions could be housed together on a large pasture, because the frequency of agonistic interactions decreased quickly and remained at a minimal level from the fourth day following group integration. This housing system could potentially increase horse welfare and reduce labour associated with horse management.

Perception of emotional valence in horse whinnies

“…Horses also had their head high for a longer period of time during playbacks of unfamiliar compared to familiar whinnies, which could indicate negative emotion (but see above). Encounters between unfamiliar horses can elicit aggressive interactions while the hierarchy is being established [ 49 , 58 ]. The higher arousal elicited by unfamiliar compared to familiar whinnies might thus result from anticipation of such potential aggressive encounter.…”

Vocal expression of emotional valence in Przewalski’s horses (Equus przewalskii)

“…By contrast, negative emotions result from encounters with punishing stimuli that threaten fitness, and they result in avoidance behaviour 2 . Accordingly, we considered anticipation for food and affiliative interactions as positive contexts 5 , 42 – 45 . By contrast, social separation and agonistic interactions were considered as negative contexts 42 , 43 , 46 .…”

“…Accordingly, we considered anticipation for food and affiliative interactions as positive contexts 5 , 42 – 45 . By contrast, social separation and agonistic interactions were considered as negative contexts 42 , 43 , 46 . For the two types of interactions (affiliative and agonistic interactions), we analysed the calls produced from the moment one animal was approaching another (or for 10 s before the interaction if the approach took longer) until 10 s after the interaction ended.…”

Behaviour of horses in a judgment bias test associated with positive or negative reinforcement

“…According to this equation, a horse would obtain a general score of 300 if it always scored 3 for one behaviour, a general score of 200 if it always scores 2, and a general score of 100 if it always scores 1 (range = 100-300; for the example above, the general score would be (4.3 × 1) + (2.1 × 2) + (93.6 × 3) = 289.4). Higher scores for body tension (more motivation), for attitude towards trainer (more contact with the trainer) and for ear position (ears more forward) thus suggested a more often positive emotional state, while higher scores for head level (head higher) suggested a more often negative emotional state (Briefer Freymond et al, 2013;McDonnell and Haviland, 1995;Rietmann et al, 2004;Visser et al, 2009).…”