Jowett S L, Silk M J, Lee V, Turner S P, Camerlink I
Institute of Genetics and Animal Biotechnology of the Polish Academy of Sciences, Postępu 36a, 05-552 Jastrzębiec, Poland.
Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
Animal. 2025 Aug;19(8):101585. doi: 10.1016/j.animal.2025.101585. Epub 2025 Jun 19.
Affiliation as indicated by proximity has, to date, been used as the principal measure of positive relationships in farm animals. However, intensive housing may present a caveat to using proximity as a representation of affiliation as animals may be forced into proximity by stocking densities. To investigate affiliation patterns, this study examined differences in the expression of proximity and contact behaviours following regrouping in pigs. Animals (61 males and 56 females) were observed across eight groups (14.6 ± 0.69 SD pigs/group). Each group comprised a mix of familiar and unfamiliar finishing pigs (12 weeks old). Video observations occurred for two consecutive days following regrouping. Individuals were continuously observed for social nosing behaviour for 2 h in total, balanced across days. Social network analysis of directed networks provided group-level information including weighted degree centrality and density. Exponential Random Graph Models fitted to these networks were used to consider the underpinning social processes including reciprocity, homophily, and the effect of individual attributes. Groups differed in the expression of behaviours, whilst, at the global level, density was significantly lower (P < 0.001) for the snout-snout (0.68 ± 0.15 SD) than snout-head (0.92 ± 0.04 SD) proximity networks. Statistically significant differences were also shown in the density across the contact networks (P < 0.001) with the lowest cohesion in the snout-snout (0.33 ± 0.14 SD), compared to the snout-head (0.52 ± 0.07 SD), and snout-body (0.66 ± 0.09 SD) contact networks. Familiarity was a predictor of interaction (P = 0.0001) across behaviours. Familiar pigs were nearly twice as likely to assort in the contact networks and three times more likely to assort in the snout-snout and snout-head proximity networks. Sex was not a predictor of snout proximity; however, females received significantly less behaviour than males in the snout-snout (odds ratio (OR): 0.78, P = 0.046), and snout-head (OR: 0.69, P = 0.001) contact networks. Snout proximity behaviours showed significant reciprocity (snout head: OR = 2.56; P = 0.008; snout-snout: OR = 2.80; P = 0.0001). Contact behaviours showed significant reciprocity in the snout-snout (OR = 2.40; P = 0.0001), and snout-head (OR = 1.55; P = 0.004) networks. Our study highlights behavioural nuances, with groups differing in snout proximity and contact patterns, in which reciprocation is normal behaviour, and snout-snout proximity and snout-snout contact are the least observed. Furthermore, it shows the influence of attributes on network structure to inform grouping strategies.
迄今为止，接近程度所表明的从属关系一直被用作衡量农场动物积极关系的主要指标。然而，集约化养殖可能会对将接近程度作为从属关系的一种体现提出警示，因为动物可能会由于饲养密度而被迫接近。为了研究从属模式，本研究考察了猪重新分组后接近行为和接触行为表达的差异。观察了八组动物（61只雄性和56只雌性）（每组14.6±0.69标准差头猪）。每组由熟悉和不熟悉的育肥猪（12周龄）混合组成。重新分组后连续两天进行视频观察。对个体进行总共2小时的社交嗅探行为连续观察，时间在两天内均衡分布。对有向网络进行社会网络分析，提供了包括加权度中心性和密度在内的群体水平信息。拟合这些网络的指数随机图模型用于考虑潜在的社会过程，包括互惠性、同质性以及个体属性的影响。各组在行为表达上存在差异，同时，在总体水平上，口鼻对口鼻（0.68±0.15标准差）接近网络的密度显著低于口鼻对头（0.92±0.04标准差）接近网络（P<0.001）。接触网络的密度也显示出统计学上的显著差异（P<0.001），口鼻对口鼻接触网络（0.33±0.14标准差）的凝聚力最低，相比之下，口鼻对头（0.52±0.07标准差）和口鼻对身体（0.66±0.09标准差）接触网络的凝聚力较高。熟悉程度是各种行为中互动的一个预测因素（P=0.0001）。熟悉的猪在接触网络中分类的可能性几乎是不熟悉猪的两倍，在口鼻对口鼻和口鼻对头接近网络中分类的可能性则是不熟悉猪的三倍。性别不是口鼻接近程度的预测因素；然而，在口鼻对口鼻（优势比（OR）：0.78，P=0.046）和口鼻对头（OR：0.69，P=0.001）接触网络中，雌性接受的行为显著少于雄性。口鼻接近行为显示出显著的互惠性（口鼻对头：OR=2.56；P=0.008；口鼻对口鼻：OR=2.80；P=0.0001）。接触行为在口鼻对口鼻（OR=2.40；P=0.0001）和口鼻对头（OR=1.55；P=0.004）网络中显示出显著的互惠性。我们的研究突出了行为上的细微差别，各组在口鼻接近和接触模式上存在差异，其中互惠是正常行为，而口鼻对口鼻接近和口鼻对口鼻接触是最少观察到的。此外，它还显示了个体属性对网络结构的影响，为分组策略提供参考。
