Dominance relationships between collared peccaries Pecari tajacu (Cetartiodactyla: Tayassuidae) in intensive breeding system

•We analyse dominance in collared peccary with Elo-rating and modified I&SI.•Top-ranking individuals are always adult females.•Some groups present a linear hierarchy, other do not.•Agonistic interactions do not increase after removing parents and introducing males. The collared peccary (Pecari tajacu) is a species with great potential for breeding in captivity since it adapts well to a variety of foods, has a high breeding capacity and there is an existing market for its meat and leather, which is of excellent quality. However, it is necessary to understand its social structure, when maintained in intensive breeding, to adequately manage groups and limit potential aggressions to the stockman. Four family units (dam, sire and descendants) were monitored (phase 1); females descendants were subsequently relocated into four new experimental social groups (phase 2). In these experimental groups, the female descendants were grouped with adult males, without the presence of the parents. Interactions were filmed three times per week, during two months, for each treatment (phase 1=family units and phase 2=experimental groups). A matrix of aggressive and submissive behaviors was developed and the dominance relations were evaluated with the Elo-rating method. A stability index of rank orders, the steepness and the degree of linearity were calculated to analyse the hierarchy in each family unit and experimental group. The parents remained on the highest hierarchical levels in three of the four family units and female descendants occupied the highest hierarchical levels in experimental groups. A linear hierarchy composed of adults of both genders was found in two family units and a mono-sexual linear hierarchy with females at the highest-ranking positions was evidenced in two experimental groups. Hierarchy was stable (all stability indexes values≥0.94), while steepness was variable among family units and experimental groups (range: 0.23–0.84). The ranking-position of a female descendant in a family unit was not a good predictor of her ranking position in experimental units. Male descendants received significantly less friendly behaviors than female descendants did (p=0.01), dams (p