Association networks and social temporal dynamics in ewes and lambs

Abstract Sheep are highly social domesticated animals that evolved to live in large and structured groups. As in other group-living species, individuals differ in the level of association they have with others, and these associations often result in lasting and stable social bonds. However, there are substantial gaps in our knowledge of the temporal social dynamics in sheep, and how their social bonds vary in relation to environmental changes. Here, we aimed to assess the social relationships between ewes and lambs, collecting dyadic associations data of 41 ewes and 55 lambs through the use of proximity loggers on a commercial farm. We computed association indices between each pair of animals to estimate the proportion of time any two individuals associated. We first generated an aggregated network of the whole 13-day observation period, and we compared the values of association indices between different types of dyads (i.e., lamb-mother, lamb-ewe non-mother, lambs littermates, lambs non-littermates, ewe-ewe). We generated aggregated contact networks on a daily scale to compare the ego-networks of individuals obtained in successive time windows to determine how stable social associations were over time. As would be expected, the highest values of association indices were found in dyads formed by dams and lambs (0.17 ± 0.11) and by lambs of the same litter (0.32 ± 0.09). Both single-born and twin-born lambs showed high association values with their dams (single-born: 0.24 ± 0.11; twin-born: 0.1 ± 0.05), although twin-born lambs had stronger associations with their littermates compared with those with their mothers (p-value