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Invited review: Social dominance in dairy cattle: A critical review with guidelines for future research

Open AccessPublished:December 29, 2022DOI:https://doi.org/10.3168/jds.2022-22534

      ABSTRACT

      Cattle are gregarious animals able to form social relationships. Dominance is one of the most widely studied social behaviors of dairy cattle, especially cows confined indoors. However, much of the past dairy cattle research has used an unstandardized approach, differing in definitions and conceptual understanding of dominance, as well as their methods of data collection and dominance calculation. The first of the 3 aims of this review is to evaluate how dominance relates to the social behavior of housed dairy cows. Cows engage in agonistic interactions to establish and reinforce dominance relationships. An individual's dominance is influenced by intrinsic characteristics, such as personality, and extrinsic factors, including group composition. When competing for resources, agonistic interactions can also be influenced by individual motivational differences, such as hunger, which may diminish the role of dominance in regulating competition. Our second aim is to critically review methods used to assess dominance in cows. This includes discussions on the effect of time and location of data collection on measured values as well as the viability and limitations of some dominance calculation methods. We propose that different methodologies lend themselves to different types of research questions. For example, the use of data stream-based methods that consider the sequence of interactions are useful for estimating how dominance fluctuates with changing conditions and can be used in a dynamically changing group. In contrast, matrix-based methods that aggregate social interactions may be best for identifying the social position of individuals and understanding how social characteristics influence the attributes of a stable hierarchy. Our third aim is to discuss the future of dominance research. We use a flowchart to illustrate guidelines for a more standardized approach to measuring dominance in cattle. We also identify areas in need of further conceptual clarification, suggest practical applications of dominance when managing dairy cattle, and discuss some limitations of dominance research.

      Key words

      INTRODUCTION

      A dominance relationship can be described as a “pattern of repeated, agonistic interactions between two individuals, characterized by a consistent outcome in favor of the same dyad member and a default yielding response of its opponent rather than escalation” (
      • Schjelderup-Ebbe T.
      Beitrage zur sozialpsychologie des haushuns (trans. M Schleidt, WM Schleidt).
      ;
      • Drews C.
      The concept and definition of dominance in animal behavior.
      ). Dominance differs between species and societies, being influenced by differences in fitness costs and benefits associated with social position (
      • Goymann W.
      • Wingfield J.C.
      Allostatic load, social status, and stress hormones: The costs of social status matter.
      ) and species-specific social conventions (reviewed in
      • Strauss E.D.
      • Shizuka D.
      The dynamics of dominance: Open questions, challenges, and solutions.
      ). For instance, non-nepotistic (e.g., ruminant) and kinship-based (e.g., many Old World nonhuman primate species) societies involve different means of attaining social position (e.g.,
      • Kawai M.
      On the rank system in a natural group of Japanese monkey (I).
      ;
      • Clutton-Brock T.H.
      • Albon S.D.
      • Gibson R.M.
      • Guinness F.E.
      The logical stag: Adaptive aspects of fighting in red deer (Cervus elaphus L).
      ;
      • Holekamp K.E.
      • Smale L.
      Dominance acquisition during mammalian social development: The “inheritance” of maternal rank.
      ). This review discusses dominance in non-nepotistic societies, focusing on confined dairy cattle.
      Dominance in cattle was first discussed by
      • Woodbury A.M.
      Changing the “hook-order” in cows.
      who introduced the terms hook order and bunt order to describe the social hierarchy arising from agonistic interactions of horned and dehorned cattle, respectively.
      • Woodbury A.M.
      Changing the “hook-order” in cows.
      noted that when the horns were removed, the qualities of the boss cow shifted from horn-facilitated characteristics to ones of strength and tenacity. The first systematic exploration of dominance in cattle was undertaken by
      • Schein M.W.
      • Fohrman M.H.
      Social dominance relationships in a herd of dairy cattle.
      , who compiled the outcomes of agonistic interactions on pasture into a winner-loser matrix, noting that the resulting distribution reflected a pattern more likely to represent dominance than chance alone. Dominance of confined cattle was first investigated by
      • Beilharz R.G.
      • Mylrea P.J.
      ; involving dairy heifers) and further described by
      • Dickson D.P.
      • Wieckert D.A.
      • Barr G.R.
      Social relationship of dairy cows in a feed lot.
      ; involving lactating cows); both groups of researchers developed an ethogram for capturing agonistic behaviors of confined cattle. Much of the research on dominance in dairy cattle, in line with typical housing practices, has since been conducted on confined groups composed only of females.
      Differences in how scholars conceptualize and operationalize dominance has led to spirited debate. For instance,
      • Beilharz R.G.
      • Zeeb K.
      Social dominance in dairy cattle.
      critiques of the mathematical approaches and discussions regarding the relationship between aggression and dominance in previous research (including work by
      • Syme C.J.
      Competitive orders as measures of social dominance.
      and
      • Friend T.H.
      • Polan C.E.
      Competitive order as a measure of social dominance in dairy cattle.
      ) were in turn systematically critiqued by
      • Syme G.J.
      • Syme L.A.
      Social dominance—A straw man revisited?: Some comments on the paper by Beilharz and Zeeb.
      . This discussion continued into the early 1990s, with additional contributions by
      • Kondo S.
      • Hurnik J.F.
      Stabilization of social hierarchy in dairy cows.
      and
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      , who noted that social stability and agonistic relationships are influenced by factors including social mixing, stocking density, and housing design. Approximately 2 decades later,
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ,
      • Val-Laillet D.
      • Veira D.M.
      • von Keyserlingk M.A.G.
      Short communication: Dominance in free-stall-housed dairy cattle is dependent upon resource.
      ) summarized many of the conceptual conundrums present in past research, and showed how different methodologies for calculating dominance can lead to different outcomes. More recently,
      • Foris B.
      • Thompson A.J.
      • von Keyserlingk M.A.G.
      • Melzer N.
      • Weary D.M.
      Automatic detection of feeding and drinking related agonistic behavior and dominance in dairy cows.
      ,
      • Foris B.
      • Lecorps B.
      • Krahn J.
      • Weary D.M.
      • von Keyserlingk M.A.G.
      The effects of cow dominance on the use of a mechanical brush.
      ) revisited the discussion of dominance in cattle, calling for practical solutions to overcome issues concerning data collection and calculation methods, but many questions remain unanswered (
      • Strauss E.D.
      • Curley J.P.
      • Shizuka D.
      • Hobson E.A.
      The centennial of the pecking order: Current state and future prospects for the study of dominance hierarchies.
      ).
      This review has 3 aims: first, to investigate contemporary understanding of the concept of dominance in dairy cattle, focusing primarily on cattle kept in confined housing systems; second, to critically review methods commonly used to assess dominance in cattle; and third, to discuss future directions for dominance research, including ways of measuring dominance, the need for further conceptual clarification, and ways of applying the measures and concepts to improve cattle management and welfare.
      Because no human or animal subjects were used, this analysis did not require approval by an Institutional Animal Care and Use Committee or Institutional Review Board.

      THE CONCEPT OF DOMINANCE

      Dominance is generally accepted to be multidimensional and can be considered on 3 levels (
      • Langbein J.
      • Puppe B.
      Analysing dominance relationships by sociometric methods—A plea for a more standardised and precise approach in farm animals.
      ): (1) the asymmetric agonistic relationship between a pair of animals (dyad); (2) the overall network of dyadic-dominance relationships between individuals within a group (dominance hierarchy;
      • Chase I.D.
      • Seitz K.
      Self-structuring properties of dominance hierarchies. A new perspective.
      ); and (3) the experience of the individual within the dominance structure (
      • Drews C.
      The concept and definition of dominance in animal behavior.
      ;
      • Chase I.D.
      • Tovey C.
      • Spangler-Martin D.
      • Manfredonia M.
      Individual differences versus social dynamics in the formation of animal dominance hierarchies.
      ).

      Dyadic Level

      Dyadic relationships can be classified as one-way (one animal always dominates the other) or 2-way (both animals dominate the other on at least one occasion, with varying degrees of asymmetry;
      • Hand J.L.
      Resolution of social conflicts: Dominance, egalitarianism, spheres of dominance, and game theory.
      ;
      • Drews C.
      The concept and definition of dominance in animal behavior.
      ;
      • Chase I.D.
      • Tovey C.
      • Spangler-Martin D.
      • Manfredonia M.
      Individual differences versus social dynamics in the formation of animal dominance hierarchies.
      ;
      • Langbein J.
      • Puppe B.
      Analysing dominance relationships by sociometric methods—A plea for a more standardised and precise approach in farm animals.
      ). Similar to other ungulates (e.g., goats), cattle appear to establish and reinforce dominance relationships through ritualistic (
      • Bryant J.
      The social environment: Behavior and stress in housed livestock.
      ) low-cost agonistic behaviors (
      • Barroso F.G.
      • Alados C.L.
      • Boza J.
      Social hierarchy in the domestic goat: Effect on food habits and production.
      ;
      • Langbein J.
      • Puppe B.
      Analysing dominance relationships by sociometric methods—A plea for a more standardised and precise approach in farm animals.
      ), transitioning from physical to nonphysical (i.e., threat behaviors) as relationships become established (
      • Kondo S.
      • Hurnik J.F.
      Stabilization of social hierarchy in dairy cows.
      ). In cattle, dyadic relationships are expected to be stable with time (
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ;
      • Foris B.
      • Thompson A.J.
      • von Keyserlingk M.A.G.
      • Melzer N.
      • Weary D.M.
      Automatic detection of feeding and drinking related agonistic behavior and dominance in dairy cows.
      ). Affiliative behaviors may also play a role in reinforcing dominance relationships by improving familiarization between individuals, creating positive social bonds that encourage resource sharing (
      • Puppe B.
      Effects of familiarity and relatedness on agonistic pair relationships in newly mixed domestic pigs.
      ;
      • Górecki M.T.
      • Sochacka J.
      • Kaźmierczak S.
      Dominance hierarchy, milking order, and neighbour preference in domestic goats.
      ) and result in preferential interaction partners (
      • Gutmann A.K.
      • Špinka M.
      • Winckler C.
      Long-term familiarity creates preferred social partners in dairy cows.
      ).

      Hierarchy (Group) Level

      Hierarchies are an emergent property of dyadic-dominance relationships (
      • Schjelderup-Ebbe T.
      Beitrage zur sozialpsychologie des haushuns (trans. M Schleidt, WM Schleidt).
      ). Dominance establishment and reinforcement within a hierarchy are influenced by self-organizing social dynamics such as bystander effects (i.e., third-party observation of interactions between groupmates) that can cause the relationships that form within a group to differ from those same relationships when the dyad is isolated (
      • Oliveira R.F.
      • Lopes M.
      • Carneiro L.A.
      • Cana'rio A.V.M.
      Watching fights raises fish hormone levels.
      ;
      • Chase I.D.
      • Tovey C.
      • Spangler-Martin D.
      • Manfredonia M.
      Individual differences versus social dynamics in the formation of animal dominance hierarchies.
      ). The hierarchies that form in groups of cattle are expected to be stable within a given social environment (
      • Chase I.D.
      • Tovey C.
      • Spangler-Martin D.
      • Manfredonia M.
      Individual differences versus social dynamics in the formation of animal dominance hierarchies.
      ;
      • Estevez I.
      • Andersen I.L.
      • Nævdal E.
      Group size, density, and social dynamics in farm animals.
      ). However, compared with groups on pasture, when cattle are confined indoors, hierarchies appear to be less linear (i.e., lower proportion of transitive of relationships;
      • O'Connell J.
      • Giller P.S.
      • Meaney W.
      A comparison of dairy cattle behavioural patterns at pasture and during confinement.
      ;
      • Chase I.D.
      • Tovey C.
      • Spangler-Martin D.
      • Manfredonia M.
      Individual differences versus social dynamics in the formation of animal dominance hierarchies.
      ;
      • Šárová R.
      • Špinka M.
      • Stěhulová I.
      • Ceacero F.
      • Šimečková M.
      • Kotrba R.
      Pay respect to the elders: Age, more than body mass, determines dominance in female beef cattle.
      ) with lower steepness (i.e., smaller dominance differences between individuals;
      • Reinhardt C.
      • Reinhardt A.
      • Reinhardt V.
      Social behaviour and reproductive performance in semi-wild Scottish Highland cattle.
      ;
      • de Vries H.
      • Stevens J.M.G.
      • Vervaecke H.
      Measuring and testing the steepness of dominance hierarchies.
      ;
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ). Although it is unknown how animals perceive dominance within their hierarchy (
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ), social position has been suggested to be associated with the patterns of agonistic behavior (
      • Hobson E.A.
      • Mønster D.
      • DeDeo S.
      Aggression heuristics underlie animal dominance hierarchies and provide evidence of group-level social information.
      ;
      • Strauss E.D.
      • Shizuka D.
      The dynamics of dominance: Open questions, challenges, and solutions.
      ). For instance, cattle are suggested to more frequently engage in patterns of close-competition (i.e., smaller rank differences between individuals in agonistic interactions;
      • Reinhardt V.
      • Reinhardt A.
      Dynamics of social hierarchy in a dairy herd.
      ;
      • Kondo S.
      • Hurnik J.F.
      Stabilization of social hierarchy in dairy cows.
      ) than bullying (i.e., greater rank difference between individuals in agonistic interactions; Hobson et al., 2021;
      • Strauss E.D.
      • Shizuka D.
      The dynamics of dominance: Open questions, challenges, and solutions.
      ). Socio-positive bonds such as friendship may encourage resource sharing in which case dyadic agonistic interactions may generally be mutual and less aggressive, leading to overall small differences in dominance. We encourage further research to investigate both affiliative and agonistic bonds in groups of cattle with varying levels of familiarity to disentangle these effects.

      Individual Level

      An individual's dominance is a representation of their experience within the hierarchy and is generally described in 1 of 2 ways: an individually determined cardinal dominance score, or an ordinal rank that denotes the animal's position within the hierarchy relative to others (
      • Strauss E.D.
      • Holekamp K.E.
      Inferring longitudinal hierarchies: Framework and methods for studying the dynamics of dominance.
      ). Both representations provide an estimation of an individual's dominance strength (
      • Albers P.C.H.
      • De Vries H.
      Elo-rating as a tool in the sequential estimation of dominance strengths.
      ). In the absence of knowledge of a group's social dynamics, or dominance scores, ordinal ranking risks sacrificing information about factors, such as the hierarchy distribution (
      • Langbein J.
      • Puppe B.
      Analysing dominance relationships by sociometric methods—A plea for a more standardised and precise approach in farm animals.
      ). Dominance scores offer particular benefits as they can be used to determine ranks, whereas ranks cannot be used to determine scores; thus, ranks and scores provide different and complimentary information. When used together, ranks and scores likely offer a more complete interpretation of social dynamics and individual experience than either method alone. Individual-level dominance is often expected to be temporally stable and consistent across varying circumstances (
      • Réale D.
      • Reader S.M.
      • Sol D.
      • McDougall P.T.
      • Dingemanse N.J.
      Integrating animal temperament within ecology and evolution.
      ); a phenomenon that is viewed by some as a personality trait (e.g.,
      • Finkemeier M.A.
      • Langbein J.
      • Puppe B.
      Personality research in mammalian farm animals: Concepts, measures, and relationship to welfare.
      ) similar to the big five personality traits in animals: exploration, sociability, boldness, aggressiveness, and activity (see
      • John O.P.
      The “Big Five” factor taxonomy: Dimensions of personality in the natural language and in questionnaires.
      ;
      • Costa Jr., P.T.
      • McCrae R.R.
      The five-factor model of personality and its relevance to personality disorders.
      , for reviews).

      FACTORS THAT INFLUENCE DOMINANCE

      Dominance can be described as a dynamic social outcome (
      • Syme G.J.
      • Syme L.A.
      Social dominance—A straw man revisited?: Some comments on the paper by Beilharz and Zeeb.
      ;
      • Tibbetts E.A.
      • Pardo-Sanchez J.
      • Weise C.
      The establishment and maintenance of dominance hierarchies.
      ), influenced by multiple factors, including those that are intrinsic (e.g., personality traits), and extrinsic (e.g., past experiences;
      • Landau H.G.
      On dominance relations and the structure of animal societies: I. Effect of inherent characteristics.
      ;
      • Dugatkin L.A.
      Winner and loser effects and the structure of dominance hierarchies.
      ). Confounding factors such as motivation may, however, diminish the role of dominance in maintaining social order (
      • Beilharz R.G.
      • Zeeb K.
      Social dominance in dairy cattle.
      ;
      • Goymann W.
      • Wingfield J.C.
      Allostatic load, social status, and stress hormones: The costs of social status matter.
      ).

      Intrinsic Factors

      Although dominance can only be expressed in a social environment, it includes individual characteristics independent of group dynamics and competitive context (
      • Drews C.
      The concept and definition of dominance in animal behavior.
      ). Coined as the prior attributes hypothesis,
      • Chase I.D.
      • Tovey C.
      • Spangler-Martin D.
      • Manfredonia M.
      Individual differences versus social dynamics in the formation of animal dominance hierarchies.
      suggested that dominance relationships and hierarchies form on the basis of pre-existing attributes that determine an individual's dominance ability (i.e., resource holding potential;
      • Parker G.A.
      Assessment strategy and the evolution of fighting behavior.
      ;
      • Dugatkin L.A.
      Winner and loser effects and the structure of dominance hierarchies.
      ). These attributes are species-dependent and, in cattle, may include physical (e.g., size;
      • Phillips C.J.C.
      • Rind M.I.
      The effects of social dominance on the production and behavior of grazing dairy cows offered forage supplements.
      ) and temporal (e.g., age;
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ) characteristics, as well as nonphysical components, such as behavior and personality (e.g., aggression, boldness, sociability;
      • Réale D.
      • Reader S.M.
      • Sol D.
      • McDougall P.T.
      • Dingemanse N.J.
      Integrating animal temperament within ecology and evolution.
      ;
      • de Sousa K.T.
      • Machado Filho L.C.P.
      • Bica G.S.
      • Deniz M.
      • Hötzel M.J.
      Degree of affinity among dairy heifers affects access to feed supplementation.
      ).

      Extrinsic Factors

      Past experiences can influence dominance in the form of winner and loser effects (
      • Landau H.G.
      On dominance relations and the structure of animal societies: I. Effect of inherent characteristics.
      ;
      • Dugatkin L.A.
      Winner and loser effects and the structure of dominance hierarchies.
      ). Reinforcement learning can alter an animal's perceived probability of success in an agonistic interaction (
      • Landau H.G.
      On dominance relations and the structure of animal societies: I. Effect of inherent characteristics.
      ;
      • Dugatkin L.A.
      Winner and loser effects and the structure of dominance hierarchies.
      ); an animal that succeeds/fails in obtaining a reward (e.g., resource access) following engagement in agonistic behavior is more/less likely to engage in those behaviors in the future (
      • Landau H.G.
      On dominance relations and the structure of animal societies: I. Effect of inherent characteristics.
      ;
      • Dugatkin L.A.
      Winner and loser effects and the structure of dominance hierarchies.
      ; e.g., chickens,
      • Newberry R.
      • Cloutier S.
      Recent social experience, body weight, and initial patterns of attack predict the social status attained by unfamiliar hens in a new group.
      ; pigs,
      • Oldham L.
      • Camerlink I.
      • Arnott G.
      • Doeschl-Wilson A.
      • Farish M.
      • Turner S.P.
      Winner–loser effects overrule aggressiveness during the early stages of contests between pigs.
      ). Winner and loser effects likely also affect a cow's success in future agonistic interactions (e.g.,
      • Kondo S.
      • Hurnik J.F.
      Stabilization of social hierarchy in dairy cows.
      ), but experimental work is needed to test this prediction.
      Dominance may also change based on social context (
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ;
      • Drews C.
      The concept and definition of dominance in animal behavior.
      ). When social environment factors (e.g., group composition and size) change, different traits, strategies (e.g.,
      • Foris B.
      • von Keyserlingk M.A.G.
      • Weary D.M.
      Competition strategies of metritic and healthy transition cows.
      ), and experiences may cause animals to become more or less dominant based on the social strategies of others within the environment (e.g., game theory;
      • Maynard Smith J.
      The theory of games and the evolution of animal conflicts.
      ;
      • Hand J.L.
      Resolution of social conflicts: Dominance, egalitarianism, spheres of dominance, and game theory.
      ;
      • Tibbetts E.A.
      • Pardo-Sanchez J.
      • Weise C.
      The establishment and maintenance of dominance hierarchies.
      ). For example, removing the most dominant or most aggressive animal in a group may alter the dominance hierarchy (e.g., cichlid fish,
      • Chase I.D.
      • Tovey C.
      • Spangler-Martin D.
      • Manfredonia M.
      Individual differences versus social dynamics in the formation of animal dominance hierarchies.
      ) and individual experiences of the animals remaining in the group (e.g., cows,
      • Woodbury A.M.
      Changing the “hook-order” in cows.
      ). Similarly, increased group size can cause individual recognition of other group members to become more difficult and reduce the frequency of interactions between individuals (
      • Pagel M.
      • Dawkins M.S.
      Peck orders and group size in laying hens: ‘Futures contracts’ for non-aggression.
      ), leading to situations where dominance relationships are either absent or only weakly established (e.g.,
      • Estevez I.
      • Newberry R.
      • Rayna L.
      Broiler chickens: A tolerant social system?.
      ,
      • Estevez I.
      • Keeling L.J.
      • Newberry R.C.
      Decreasing aggression with increasing group size in young domestic fowl.
      ). Even though the effect of group size on individual recognition and dominance in cattle has been discussed (e.g.,
      • Fraser A.F.
      • Broom D.M.
      Farm Animal Behaviour and Welfare.
      ;
      • Grant R.J.
      • Albright J.L.
      Effect of animal grouping on feeding behavior and intake of dairy cattle.
      ), it has not been experimentally investigated.

      Confounding Factors

      Engagement in agonistic interactions appear to follow the predictions of state-dependent cost-benefit analysis that consider potential costs to the animal of engaging in the interaction (e.g., energetic expense, potential injury) as well as the potential benefits (e.g., resource access;
      • Goymann W.
      • Wingfield J.C.
      Allostatic load, social status, and stress hormones: The costs of social status matter.
      ). Variation in motivation (or other state-dependent factors) among individuals in the group can alter the value of resources. Individuals with increased motivation for a resource may become more competitively successful, potentially resulting in agonistic interactions contrary to established dominance relationships (
      • Beilharz R.G.
      • Zeeb K.
      Social dominance in dairy cattle.
      ;
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ). Changes in motivation can occur on different temporal scales and to different magnitudes. These changes are likely most common in agonistic interactions for access to resources that are limited or change in quality with time, such as fresh feed (
      • DeVries T.J.
      • Von Keyserlingk M.A.G.
      • Beauchemin K.A.
      Frequency of feed delivery affects the behavior of lactating dairy cows.
      ;
      • Miller-Cushon E.K.
      • DeVries T.J.
      Feed sorting in dairy cattle: Causes, consequences, and management.
      ;
      • McConnachie E.
      • Smid A.M.C.
      • Thompson A.J.
      • Weary D.M.
      • Gaworski M.A.
      • von Keyserlingk M.A.G.
      Cows are highly motivated to access a grooming substrate.
      ). Similarly, as competition for available resources increases (due to limited resource quantity or quality, increased stocking density, or increased need) there is an increase in the number of agonistic interactions between cows at the resource (feed bunk,
      • Krawczel P.D.
      • Klaiber L.B.
      • Butzler R.E.
      • Klaiber L.M.
      • Dann H.M.
      • Mooney C.S.
      • Grant R.J.
      Short-term increases in stocking density affect the lying and social behavior, but not the productivity, of lactating Holstein dairy cows.
      ; lying stalls,
      • Fregonesi J.A.
      • Tucker C.B.
      • Weary D.M.
      Overstocking reduces lying time in dairy cows.
      ; drinker,
      • Coimbra P.A.D.
      • Machado Filho L.C.P.
      • Hötzel M.J.
      Effects of social dominance, water trough location, and shade availability on drinking behavior of cows on pasture.
      ). Increased competition may reflect changes in motivation that potentially disrupt social stability and reduce the role of the dominance hierarchy at regulating agonistic interactions (
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ). The effects of these motivational factors on the outcomes of dyadic agonistic relationships remain largely unexplored in cattle (e.g.,
      • Tennessen T.
      • Gonyou H.W.
      Comparing social dominance for different traits in cattle. The 61st annual feeders' day report.
      ;
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ).

      INTERACTIONS USED IN DOMINANCE CALCULATIONS

      The most common form of dominance assessment relies only on agonistic behaviors that begin with a physical altercation and end with a clear winner or loser (e.g.,
      • Schein M.W.
      • Fohrman M.H.
      Social dominance relationships in a herd of dairy cattle.
      ;
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ). However, dominance relationships can be more nuanced (
      • Hand J.L.
      Resolution of social conflicts: Dominance, egalitarianism, spheres of dominance, and game theory.
      ), potentially including nonphysical factors such as avoidance (
      • Kondo S.
      • Hurnik J.F.
      Stabilization of social hierarchy in dairy cows.
      ), inhibitory controlling behaviors (
      • Beilharz R.G.
      • Zeeb K.
      Social dominance in dairy cattle.
      ), and affiliative interactions (
      • Val-Laillet D.
      • Guesdon V.
      • von Keyserlingk M.A.G.
      • de Passillé A.M.
      • Rushen J.
      Allogrooming in cattle: Relationships between social preferences, feeding displacements, and social dominance.
      ;
      • Creel S.
      • Dantzer B.
      • Goymann W.
      • Rubenstein D.R.
      The ecology of stress: Effects of the social environment.
      ;
      • de Sousa K.T.
      • Machado Filho L.C.P.
      • Bica G.S.
      • Deniz M.
      • Hötzel M.J.
      Degree of affinity among dairy heifers affects access to feed supplementation.
      ). Some of these behaviors may be difficult for researchers to observe and measure (e.g.,
      • Boissy A.
      • Terlouw C.
      • Le Neindre P.
      Presence of cues from stressed conspecifics increases reactivity to aversive events in cattle: Evidence for the existence of alarm substances in urine.
      ). Whether these behaviors are important in dominance relationships in cattle remains unknown and is a topic worthy of future research.
      Agonistic interactions between cows differ in type (
      • Dickson D.P.
      • Wieckert D.A.
      • Barr G.R.
      Social relationship of dairy cows in a feed lot.
      ) and severity. These interactions potentially represent different aspects of dominance (e.g., relationship establishing vs. reinforcing;
      • Kondo S.
      • Hurnik J.F.
      Stabilization of social hierarchy in dairy cows.
      ) and may also be unrelated to dominance (e.g., indiscriminate social competition). The varied dominance-value of different types of interactions, and the factors that may influence these differences, has not been systematically considered in cattle dominance research.
      In intensive dairy cattle systems, most agonistic interactions occur at the feeding area (i.e., feed bunk;
      • Val-Laillet D.
      • Veira D.M.
      • von Keyserlingk M.A.G.
      Short communication: Dominance in free-stall-housed dairy cattle is dependent upon resource.
      ;
      • Foris B.
      • Thompson A.J.
      • von Keyserlingk M.A.G.
      • Melzer N.
      • Weary D.M.
      Automatic detection of feeding and drinking related agonistic behavior and dominance in dairy cows.
      ), with the highest frequency in the hours after fresh-feed delivery (
      • DeVries T.J.
      • von Keyserlingk M.A.G.
      • Weary D.M.
      Effect of feeding space on the inter-cow distance, aggression, and feeding behavior of free-stall housed lactating dairy cows.
      ). The agonistic interactions at the feed bunk seem to capture much of the variation between individuals when used for dominance calculations (
      • Foris B.
      • Thompson A.J.
      • von Keyserlingk M.A.G.
      • Melzer N.
      • Weary D.M.
      Automatic detection of feeding and drinking related agonistic behavior and dominance in dairy cows.
      ). However, feed-related interactions account for the vast majority of all interactions (e.g., 88%;
      • Val-Laillet D.
      • Veira D.M.
      • von Keyserlingk M.A.G.
      Short communication: Dominance in free-stall-housed dairy cattle is dependent upon resource.
      ), possibly overshadowing any differences in the relationships associated with other resources. Differences in motivation may result in differing relationships between individuals by location (
      • Hand J.L.
      Resolution of social conflicts: Dominance, egalitarianism, spheres of dominance, and game theory.
      ;
      • Nogues E.
      • Lecorps B.
      • Weary D.M.
      • von Keyserlingk M.A.G.
      Individual variability in response to social stress in dairy heifers.
      ). Even though studies have compared dominance across resources, many were based on data sets that differ in quality and comprehensiveness (e.g.,
      • Phillips C.J.C.
      Cattle Behavior.
      ;
      • Val-Laillet D.
      • Veira D.M.
      • von Keyserlingk M.A.G.
      Short communication: Dominance in free-stall-housed dairy cattle is dependent upon resource.
      ), limiting the strength of the conclusions.
      Resource-dependent motivational fluctuations may also be temporally disparate and, therefore, when data are collected may affect which relationships are observed and to what degree confounding factors contribute. Agonistic interactions for dominance calculations have been primarily measured in 1 of 2 ways: (1) single or repeat measures of the same time periods (e.g., the hours after fresh-feed delivery;
      • DeVries T.J.
      • von Keyserlingk M.A.G.
      • Weary D.M.
      Effect of feeding space on the inter-cow distance, aggression, and feeding behavior of free-stall housed lactating dairy cows.
      ), such that only certain periods of the day are represented, or (2) single or repeated bouts of observation for ≥24 h (e.g.,
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ;
      • Foris B.
      • Lecorps B.
      • Krahn J.
      • Weary D.M.
      • von Keyserlingk M.A.G.
      The effects of cow dominance on the use of a mechanical brush.
      ) or staggered observational times, such that all (or most) periods of the day are represented (e.g.,
      • Galindo F.
      • Broom D.M.
      The relationships between social behavior of dairy cows and the occurrence of lameness in three herds.
      ). Temporal differences in dairy cow behavior are well documented (e.g.,
      • DeVries T.J.
      • von Keyserlingk M.A.G.
      Feed stalls affect the social and feeding behavior of lactating dairy cows.
      ), and can be due to both context and time-dependent factors (e.g., hours after fresh-feed delivery;
      • DeVries T.J.
      • von Keyserlingk M.A.G.
      • Weary D.M.
      Effect of feeding space on the inter-cow distance, aggression, and feeding behavior of free-stall housed lactating dairy cows.
      ;
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ). Measurements during these time periods may emphasize behavioral differences that reflect changes in motivation (e.g., satiation), limiting inferences from these studies. Conducting observations for dominance calculation throughout the day at multiple resources compared with a single resource (e.g., feed bunk) may reduce some potential biases, but further research is required to substantiate this claim. How time in relation to resource availability (e.g., changes in competition) affects dominance has not been experimentally explored in cattle.

      CALCULATION METHODS

      Multiple methods have been used for calculating dominance in dairy cattle. Most methods rely on winner-loser matrices (or actor-reactor matrices) of agonistic interactions (e.g.,
      • Schein M.W.
      • Fohrman M.H.
      Social dominance relationships in a herd of dairy cattle.
      ;
      • Kondo S.
      • Hurnik J.F.
      Stabilization of social hierarchy in dairy cows.
      ) that do not enable dominance to be calculated continuously in groups that vary in size or composition (
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ). We limit our discussion to methods that provide individuals with a cardinal score rather than a rank. In the section that follows, we discuss the strengths and limitations of 4 of the most commonly used methods for quantifying dominance in cattle, as well as 2 methods newer to cattle research.

      Commonly Used Methods

      One widely used method that has been proposed as a dominance index (e.g.,
      • Tilson R.L.
      • Sweeny K.A.
      • Binczik G.A.
      • Reindl N.J.
      Buddies and bullies: Social structure of a bachelor group of Przewalski horses.
      ;
      • Galindo F.
      • Broom D.M.
      The relationships between social behavior of dairy cows and the occurrence of lameness in three herds.
      ) calculates an individual's score as the proportion of successes in all agonistic interactions (for equation, see Table 1). However, dominance is a relationship between 2 individuals and the identity of the participants in each interaction matters (
      • Mendl M.
      • Zanella A.J.
      • Broom D.M.
      Physiological and reproductive correlates of behavioral strategies in female domestic pigs.
      ;
      • Drews C.
      The concept and definition of dominance in animal behavior.
      ). Therefore, although this index may be significantly correlated with other methods in some circumstances (e.g.,
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ), it might be most appropriately deemed an agonistic success index rather than dominance.
      Table 1Methods intended to calculate dominance from agonistic interactions
      For each method, we outline equations and advantages and disadvantages when used to measure dominance. We include some examples from the cattle literature where the methods were used. This table was adapted from Hubbard et al. (2021a).
      Calculation methodAdvantages and disadvantages in dominance calculationExample
      Agonistic success index (
      • Tilson R.L.
      • Sweeny K.A.
      • Binczik G.A.
      • Reindl N.J.
      Buddies and bullies: Social structure of a bachelor group of Przewalski horses.
      ) =no.oftimestheindividualdisplacedanycowno.oftimestheindividualdisplacedanycow+no.oftimestheindividualhasbeendisplaced
      Advantages: can be used to reflect agonistic success when it is not possible to distinguish between individuals. Can be used continuously in groups of varying size and composition. Disadvantage: does not consider the identities of both individuals or dyadic relationships and, therefore, is not a true measure of dominance. More likely to be influenced by aggressiveness than other methods.
      • Galindo F.
      • Broom D.M.
      The relationships between social behavior of dairy cows and the occurrence of lameness in three herds.
      ;
      • Huzzey J.M.
      • DeVries T.J.
      • Valois P.
      • von Keyserlingk M.A.G.
      Stocking density and feed barrier design affect the feeding and social behavior of dairy cattle.
      Lamprecht index (
      • Beilharz R.G.
      • Mylrea P.J.
      ;
      • Sambraus H.H.
      Beobachtungen und Oberlegungen zur Sozialordnung yon Rindern.
      ;
      • Lamprecht J.
      Structure and causation of the dominance hierarchy in a flock of bar-headed geese (Anser indicus).
      ) =no.ofcowsanindividualdominatedno.ofcowsthatanindividualdominated+no.ofcowsthatanindividualwasdominatedby (“Dominated” indicates that the focal cow won more than they lost against an individual.)
      Advantages: becomes increasingly robust to chance with more information. Determines dominance relationship by proportional comparison. Disadvantages: risks overestimating the importance of single interactions or the asymmetricity of dyadic relationships. Cannot calculate dominance when group composition changes.
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ;
      • de Freslon I.
      • Peralta J.M.
      • Strappini A.C.
      • Monti G.
      Understanding allogrooming through a dynamic social network approach: An example in a group of dairy cows.
      Kondo–Hurnik index (
      • Kondo S.
      • Hurnik J.F.
      Stabilization of social hierarchy in dairy cows.
      ) =j=1nno.ofdisplacementswonno.displacementslostbycowiagainstj|no.ofdisplacementswonno.displacementslostbycowiagainstj| (i.e., summed total for all interaction partners j for focal cow i)
      Advantage: becomes increasingly robust to chance with more information. Disadvantages: risks overestimating the importance of single interactions or the asymmetry of dyadic relationships. Not calculated as a proportion or normalized to group size. Cannot calculate dominance in a group of changing composition.
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ;
      • Bica G.S.
      • Pinheiro Machado Filho L.C.
      • Teixeira D.L.
      • de Sousa K.T.
      • Hötzel M.J.
      Time of grain supplementation and social dominance modify feeding behavior of heifers in rotational grazing systems.
      Mendl index (
      • Mendl M.
      • Zanella A.J.
      • Broom D.M.
      Physiological and reproductive correlates of behavioral strategies in female domestic pigs.
      ) =no.ofcowsthatanindividualisabletodisplaceno.ofcowsthatanindividualisabletodisplace+no.ofcowsthatareabletodisplacetheindividual×100
      Advantage: determines dominance relationship by proportional comparison. Disadvantages: risks overestimating the importance of single interactions or the asymmetricity of dyadic relationships. Cannot calculate dominance in a group of changing composition. Less robust to chance with more information.
      • DeVries T.J.
      • von Keyserlingk M.A.G.
      • Weary D.M.
      Effect of feeding space on the inter-cow distance, aggression, and feeding behavior of free-stall housed lactating dairy cows.
      , 2006)
      Normalized David's score (
      • David H.A.
      Ranking from unbalanced paired-comparison data.
      ;
      • Gammell M.P.
      • de Vries H.
      • Jennings D.J.
      • Carlin C.M.
      • Hayden T.J.
      David's score: A more appropriate dominance ranking method than Clutton-Brock et al.'s index.
      ;
      • de Vries H.
      • Stevens J.M.G.
      • Vervaecke H.
      Measuring and testing the steepness of dominance hierarchies.
      ;
      • Strauss E.D.
      • Holekamp K.E.
      Inferring longitudinal hierarchies: Framework and methods for studying the dynamics of dominance.
      ) =DS+N(N1)/DS+N(N1)22N, where N = group size; DS = (w + w2) − (l + l2); w = the sum of all Dij for cow i; l = the sum of all Dji values for cow j; w2 = w weighted by the w of interaction partners; l2is l weighted by the l of interaction partners. Dij=PijPij0.5nij+1=Pijproportionofwinsobservedproportionofwinsexpectedprobabilityofproportionofwinsobserved Dji = 1 − Dij; Pij = the proportion of interactions won by cow i against j; nij = the number of interactions between i and j.
      Advantages: contains a weighting factor to limit the influence of bullying on dominance measures. Becomes increasingly robust to chance with more information. Disadvantages: cannot calculate dominance in a group of changing composition.
      • Foris B.
      • Thompson A.J.
      • von Keyserlingk M.A.G.
      • Melzer N.
      • Weary D.M.
      Automatic detection of feeding and drinking related agonistic behavior and dominance in dairy cows.
      ,
      • Foris B.
      • Zebunke M.
      • Langbein J.
      • Melzer N.
      Comprehensive analysis of affiliative and agonistic social networks in lactating dairy cattle groups.
      )
      Elo-rating (
      • Elo A.E.
      The Rating of Chess Players, Past and Present.
      ;
      • Albers P.C.H.
      • De Vries H.
      Elo-rating as a tool in the sequential estimation of dominance strengths.
      ;
      • Neumann C.
      • Duboscq J.
      • Dubuc C.
      • Ginting A.
      • Irwan A.M.
      • Agil M.
      • Widdig A.
      • Engelhardt A.
      Assessing dominance hierarchies: Validation and advantages of progressive evaluation with Elo-rating.
      ) WinnerRatingnew = WinnerRatingold + (1 − p) × k, LoserRatingnew = LoserRatingold − (1 − p) × k, where p is the expectation that the winner would replace the loser (see
      • Neumann C.
      • Duboscq J.
      • Dubuc C.
      • Ginting A.
      • Irwan A.M.
      • Agil M.
      • Widdig A.
      • Engelhardt A.
      Assessing dominance hierarchies: Validation and advantages of progressive evaluation with Elo-rating.
      ), and k is the alterable interaction constant.
      Advantages: contains a weighting factor to limit the influence of bullying on dominance measures. Temporal bias for observing how dominance changes with time. Alterable interaction constant can be used to change the value of different types of interactions at the researcher's discretion. Can be used continuously in groups of varying size and composition. Disadvantages: does not determine dominance using the outcomes of dyadic relationships, so the results may be skewed if an actor repeatedly defeats the same reactor in multiple interactions.
      • Foris B.
      • Lecorps B.
      • Krahn J.
      • Weary D.M.
      • von Keyserlingk M.A.G.
      The effects of cow dominance on the use of a mechanical brush.
      Randomized Elo-rating (
      • Elo A.E.
      The Rating of Chess Players, Past and Present.
      ;
      • Albers P.C.H.
      • De Vries H.
      Elo-rating as a tool in the sequential estimation of dominance strengths.
      ;
      • Neumann C.
      • Duboscq J.
      • Dubuc C.
      • Ginting A.
      • Irwan A.M.
      • Agil M.
      • Widdig A.
      • Engelhardt A.
      Assessing dominance hierarchies: Validation and advantages of progressive evaluation with Elo-rating.
      ;
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ) Same formula as above Elo-rating, but with order of interactions randomized instead of in temporal sequence.
      Advantages: contains a weighting factor to limit the influence of bullying on dominance measures. Increasingly robust to chance with more information. Alterable interaction constant can be used to change the value of different types of interactions at the researcher's discretion. Can be used continuously in groups of varying size and composition. Disadvantages: does not determine dominance using the outcomes of dyadic relationships, so the results may be skewed if an actor repeatedly defeats the same reactor in multiple interactions.This method has not yet been used in cows.
      1 For each method, we outline equations and advantages and disadvantages when used to measure dominance. We include some examples from the cattle literature where the methods were used. This table was adapted from
      • Hubbard A.J.
      • Foster M.J.
      • Daigle C.L.
      Social dominance in beef cattle—A scoping review.
      .
      Three other indices commonly used in cows all rely on actor-reactor matrices and account for identities of both individuals involved: the Lamprecht index, the Kondo–Hurnik index, and the Mendl index (for equations, see Table 1). These methods interpret dominance as a function of success in dyadic agonistic relationships. However, by retaining only binary information at the dyadic level (i.e., dominated or not), these methods neglect information about the individual's experience. Thus, these measures may overestimate the importance of single interactions or the degree of asymmetry of dyadic relationships (
      • Gammell M.P.
      • de Vries H.
      • Jennings D.J.
      • Carlin C.M.
      • Hayden T.J.
      David's score: A more appropriate dominance ranking method than Clutton-Brock et al.'s index.
      ;
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ;
      • Neumann C.
      • McDonald D.B.
      • Shizuka D.
      Dominance ranks, dominance ratings, and linear hierarchies: A critique.
      ).

      Newer Methods

      The normalized David's score (
      • David H.A.
      Ranking from unbalanced paired-comparison data.
      ,
      • David H.A.
      The Method of Paired Comparisons.
      ;
      • de Vries H.
      • Stevens J.M.G.
      • Vervaecke H.
      Measuring and testing the steepness of dominance hierarchies.
      ) and Elo-rating (
      • Elo A.E.
      The Rating of Chess Players, Past and Present.
      ;
      • Neumann C.
      • Duboscq J.
      • Dubuc C.
      • Ginting A.
      • Irwan A.M.
      • Agil M.
      • Widdig A.
      • Engelhardt A.
      Assessing dominance hierarchies: Validation and advantages of progressive evaluation with Elo-rating.
      ) use different approaches but do overcome some of the limitations associated with the more commonly used indices described above. Both have been found to represent dominance reliably under varying circumstances (as validated using simulated data sets,
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ).

      Normalized David's Score.

      The normalized David's score (
      • David H.A.
      Ranking from unbalanced paired-comparison data.
      ,
      • David H.A.
      The Method of Paired Comparisons.
      ;
      • de Vries H.
      • Stevens J.M.G.
      • Vervaecke H.
      Measuring and testing the steepness of dominance hierarchies.
      ), a matrix-based method, has been used in many species (e.g., dogs,
      • van der Borg J.A.
      • Schilder M.B.
      • Vinke C.M.
      • De Vries H.
      Dominance in domestic dogs: A quantitative analysis of its behavioural measures.
      ; macaques,
      • Balasubramaniam K.N.
      • Berman C.M.
      • De Marco A.
      • Dittmar K.
      • Majolo B.
      • Ogawa H.
      • Thierry B.
      • De Vries H.
      Consistency of dominance rank order: A comparison of David's scores with I&SI and Bayesian methods in macaques.
      ; dairy cows,
      • Foris B.
      • Thompson A.J.
      • von Keyserlingk M.A.G.
      • Melzer N.
      • Weary D.M.
      Automatic detection of feeding and drinking related agonistic behavior and dominance in dairy cows.
      ,
      • Foris B.
      • Zebunke M.
      • Langbein J.
      • Melzer N.
      Comprehensive analysis of affiliative and agonistic social networks in lactating dairy cattle groups.
      ). To calculate dominance, each individual is given a weighting value based on the summed total of their agonistic success against each individual. The normalized David's score is then calculated by subtracting the unweighted and a weighted sum of an individual's proportion of losses to the sum of wins and losses from the unweighted and a weighted sum of their proportion of wins for each dyad (
      • de Vries H.
      • Stevens J.M.G.
      • Vervaecke H.
      Measuring and testing the steepness of dominance hierarchies.
      ). The normalized David's score corrects for the likelihood that the interaction occurred by chance (a function of the number of interactions between the 2 animals), and is normalized to the number of animals in the group (Table 1; for further description, see
      • de Vries H.
      • Stevens J.M.G.
      • Vervaecke H.
      Measuring and testing the steepness of dominance hierarchies.
      ). This method retains more information about the individual experience than the methods described above and can also be modified to include prior knowledge about dominance status (i.e., “informed David's score”;
      • Strauss E.D.
      • Holekamp K.E.
      Inferring longitudinal hierarchies: Framework and methods for studying the dynamics of dominance.
      ). The normalized David's score becomes increasingly robust to variation as the number of interactions increase, creating a measure of dominance that is robust to temporal variation (
      • de Vries H.
      • Stevens J.M.G.
      • Vervaecke H.
      Measuring and testing the steepness of dominance hierarchies.
      ;
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ). The normalized David's score is recommended when seeking to calculate a stable and robust value of dominance for each individual in situations where there are few changes over time.

      Elo-Rating.

      The Elo-rating was initially developed as a way of rating chess players (
      • Elo A.E.
      The Rating of Chess Players, Past and Present.
      ) and has recently been applied to animals, including nonhuman primates (
      • Woods J.M.
      • Ross S.R.
      • Cronin K.A.
      The social rank of zoo-housed Japanese macaques is a predictor of visitor-directed aggression.
      ), garden birds (
      • Francis M.L.
      • Plummer K.E.
      • Lythgoe B.A.
      • Macallan C.
      • Currie T.E.
      • Blount J.D.
      Effects of supplementary feeding on interspecific dominance hierarchies in garden birds.
      ), pigs (
      • Tong X.
      • Shen C.
      • Chen R.
      • Gao S.
      • Liu X.
      • Schinckel A.P.
      • Zhou B.
      Reestablishment of social hierarchies in weaned pigs after mixing.
      ), and dairy cows (
      • Foris B.
      • Lecorps B.
      • Krahn J.
      • Weary D.M.
      • von Keyserlingk M.A.G.
      The effects of cow dominance on the use of a mechanical brush.
      ). This method initially assigns all individuals the same score or different scores if there is prior knowledge about dominance status (i.e., Informed Elo;
      • Strauss E.D.
      • Holekamp K.E.
      Inferring longitudinal hierarchies: Framework and methods for studying the dynamics of dominance.
      ). After each agonistic interaction, this score is updated as a function of an individual's probability of winning (based on score differences between the individuals) multiplied by a constant, k (for further description, see
      • Albers P.C.H.
      • De Vries H.
      Elo-rating as a tool in the sequential estimation of dominance strengths.
      ). Importantly, this method does not determine dominance relationships at the dyadic level and, therefore, does not align with the widely-accepted dominance definition in
      • Drews C.
      The concept and definition of dominance in animal behavior.
      . This may result in a greater influence from some factors on Elo-rating than on dyadic-level methods, such as an actor defeating the same reactor many times in a group. However, by using the temporal sequence of interactions (in contrast to matrix-based methods), Elo-rating can be used to estimate dominance in a group of changing size and composition (Table 1;
      • Albers P.C.H.
      • De Vries H.
      Elo-rating as a tool in the sequential estimation of dominance strengths.
      ;
      • Neumann C.
      • Duboscq J.
      • Dubuc C.
      • Ginting A.
      • Irwan A.M.
      • Agil M.
      • Widdig A.
      • Engelhardt A.
      Assessing dominance hierarchies: Validation and advantages of progressive evaluation with Elo-rating.
      ), where other methods cannot be used. The Elo-rating retains more information about the individual experience than the commonly used methods described above and is sensitive to temporal variation (
      • Neumann C.
      • Duboscq J.
      • Dubuc C.
      • Ginting A.
      • Irwan A.M.
      • Agil M.
      • Widdig A.
      • Engelhardt A.
      Assessing dominance hierarchies: Validation and advantages of progressive evaluation with Elo-rating.
      ;
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ), enabling it to change quickly in relation to changes in an individual's social experience. A randomized Elo-rating (

      Neumann, C., and L. Kulik. 2014. EloRating: Animal dominance hierarchies by Elo rating. R Package Version 0.43.

      ;
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ; Table 1) is calculated using the same method as the Elo-rating but with the sequence of interactions randomly ordered (i.e., not chronological). As this latter method does not have the temporal sensitivity of Elo-rating, it estimates dominance with similar robustness to variation as the normalized David's score, while still being usable for a group of changing size and composition (for examples, see
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ;
      • Beltrão P.
      • Silva P.A.
      • Soares M.C.
      • Cardoso G.C.
      • Trigo S.
      Testosterone treatment produces sex-dependent effects in social dominance.
      ).

      CRITIQUES OF SHORT-TERM SAMPLING METHODS

      In cattle research, most studies have observed agonistic interactions either live or with video (e.g.,
      • Galindo F.
      • Broom D.M.
      The relationships between social behavior of dairy cows and the occurrence of lameness in three herds.
      ;
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ). These methods are time-consuming, and thus have resulted in measurements that are usually limited to short periods of time (a few hours), often with long intervals (days to weeks) between reassessments (e.g.,
      • Galindo F.
      • Broom D.M.
      The relationships between social behavior of dairy cows and the occurrence of lameness in three herds.
      ;
      • DeVries T.J.
      • von Keyserlingk M.A.G.
      • Weary D.M.
      Effect of feeding space on the inter-cow distance, aggression, and feeding behavior of free-stall housed lactating dairy cows.
      ), assuming some stability in dominance across measurements (e.g.,
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ;
      • Galindo F.
      • Broom D.M.
      The relationships between social behavior of dairy cows and the occurrence of lameness in three herds.
      ). Dyadic-dominance relationships are expected to be stable (e.g.,
      • Wierenga H.K.
      Social dominance in dairy cattle and the influences of housing and management.
      ); however, the outcomes of these relationships do not necessarily encapsulate all aspects of the individual experience or dominance hierarchy (
      • Chase I.D.
      • Tovey C.
      • Spangler-Martin D.
      • Manfredonia M.
      Individual differences versus social dynamics in the formation of animal dominance hierarchies.
      ), and dominance can be influenced by temporal or environmental factors (
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ;
      • Tibbetts E.A.
      • Pardo-Sanchez J.
      • Weise C.
      The establishment and maintenance of dominance hierarchies.
      ). Future research should seek to validate how an individual's dominance changes with time. The assumption of stability may be especially problematic when animals are kept in a dynamic social environment (e.g., changing group composition), which is common practice in dairy-farming systems. Currently, little is known regarding the effect of cattle group characteristics, such as size and composition, on calculation method performance. However, larger groups may yield less steep dominance hierarchies (e.g.,
      • Balasubramaniam K.N.
      • Berman C.M.
      • Ogawa H.
      • Li J.
      Using biological markets principles to examine patterns of grooming exchange in Macaca thibetana..
      ), conditions expected to decrease the reliability of dominance calculation methods, or require even larger data sets (
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ). Large group sizes may also result in a greater proportion of unknown or poorly established dominance relationships (
      • Pagel M.
      • Dawkins M.S.
      Peck orders and group size in laying hens: ‘Futures contracts’ for non-aggression.
      ;
      • Estevez I.
      • Newberry R.
      • Rayna L.
      Broiler chickens: A tolerant social system?.
      ,
      • Estevez I.
      • Keeling L.J.
      • Newberry R.C.
      Decreasing aggression with increasing group size in young domestic fowl.
      ), potentially influencing the performance of calculation methods (
      • Saccà T.
      • Gort G.
      • van de Waal E.
      • Hemelrijk C.K.
      Reducing the bias due to unknown relationships in measuring the steepness of a dominance hierarchy.
      ); further research is required in this regard.
      Problems associated with studies based on relatively few observations were highlighted by
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      . These authors simulated data sets of agonistic interactions for individuals with assigned dominance ranks and then compared the performance (e.g., rank correlation, repeatability) of dominance calculation methods across different scenarios with varying hierarchy steepness and interaction propensities. The authors concluded that a minimum of 10 (and ideally 20) times the number of interactions as the number of animals in the group were required to reliably assess dominance when at least moderate underlying hierarchy steepness can be assumed. Unfortunately, many of the studies cited above did not collect sufficient observations to meet this minimum threshold, suggesting that their conclusions should be viewed with caution. One way to facilitate the collection of larger data sets is to record agonistic interactions automatically using data from electronic feed and water bins (
      • Huzzey J.M.
      • Weary D.M.
      • Tiau B.Y.F.
      • von Keyserlingk M.A.G.
      Short communication: Automatic detection of social competition using an electronic feeding system.
      ;
      • Foris B.
      • Thompson A.J.
      • von Keyserlingk M.A.G.
      • Melzer N.
      • Weary D.M.
      Automatic detection of feeding and drinking related agonistic behavior and dominance in dairy cows.
      ;
      • McDonald P.V.
      • von Keyserlingk M.A.G.
      • Weary D.M.
      Hot weather increases competition between dairy cows at the drinker.
      ). Although, this approach also facilitates longitudinal assessments, automatic measurements of agonistic interactions at a resource can be influenced by variation in internal states (e.g., hunger), and include limitations based on assumptions (e.g., dominance being resource independent) and uncertainties during validation that should be considered and communicated transparently (e.g.,
      • Foris B.
      • Thompson A.J.
      • von Keyserlingk M.A.G.
      • Melzer N.
      • Weary D.M.
      Automatic detection of feeding and drinking related agonistic behavior and dominance in dairy cows.
      ,
      • Foris B.
      • Lecorps B.
      • Krahn J.
      • Weary D.M.
      • von Keyserlingk M.A.G.
      The effects of cow dominance on the use of a mechanical brush.
      ).

      DISCUSSION

      Guidelines for Assessing Dominance

      To aid future researchers interested in studying dominance among dairy cattle, we have provided a flowchart that outlines requirements and suggestions for measuring cattle dominance (Figure 1). This 5-step approach begins by considering the research question. Second, we outline that data collection for dominance requires that both individuals engaging in an agonistic interaction (actor and reactor) must be identified by the researcher (
      • Mendl M.
      • Zanella A.J.
      • Broom D.M.
      Physiological and reproductive correlates of behavioral strategies in female domestic pigs.
      ;
      • Drews C.
      The concept and definition of dominance in animal behavior.
      ). Third, to reliably determine dominance requires a minimum of 10 to 20 times the number of interactions as there are animals in the group assessed (
      • Sánchez-Tójar A.
      • Schroeder J.
      • Farine D.R.
      A practical guide for inferring reliable dominance hierarchies and estimating their uncertainty.
      ). If these data are not available (and more data collection is not possible), we suggest communicating the individual's score as their index value (e.g., cow A had a normalized David's score of 20), and acknowledging that the amounts of data were insufficient to determine dominance. Fourth, consider confounding factors (e.g., motivation to access a resource) that may influence measures of dominance. In this regard, further empirical research is required to determine how and whether dominance is manifested differently at different resources, levels of competition, and times of day. Finally, when calculating dominance, we encourage researchers to use methods that have been assessed for reliability and are appropriate for the intended research question. Even though the Lamprecht index, the Kondo–Hurnik index, and the Mendl index are viable methods for calculating dominance, the normalized David's score requires the same input information (i.e., an interaction matrix) and accounts for more sources of variability, likely making it the more reliable method for determining dominance in a consistent group. If the group varies in size or composition, dominance can be estimated using the temporally robust randomized Elo-rating, or temporally sensitive Elo-rating.
      Figure thumbnail gr1
      Figure 1A flowchart of guidelines for measuring dominance in cattle. This is intended as a living document that should evolve with findings from future research.

      Cattle as a Model

      All dominance relationships are governed by the same fundamental principles as animals weigh costs and benefits of social interactions with reference to internal states (e.g., hunger) and external stimuli (e.g., groupmates), although costs and benefits vary by species and context (
      • Goymann W.
      • Wingfield J.C.
      Allostatic load, social status, and stress hormones: The costs of social status matter.
      ). Although cross-species and cross-context behavioral comparisons should be made with caution (
      • Greenland S.
      • Senn S.J.
      • Rothman K.J.
      • Carlin J.B.
      • Poole C.
      • Goodman S.N.
      • Altman D.G.
      Statistical tests, P values, confidence intervals, and power: A guide to misinterpretations.
      ), studying captive cattle offers some advantages compared with free-roaming and wild populations for investigating the concept of dominance. For instance, conducting social experiments is more accessible with captive animals, especially those in production systems (such as dairy cows) that regularly experience social and environmental changes during standard on-farm management practices (
      • NFACC (National Farm Animal Care Council)
      Code of Practice for the Care and Handling of Dairy Cattle.
      ; reviewed in
      • Hubbard A.J.
      • Foster M.J.
      • Daigle C.L.
      Impact of social mixing on beef and dairy cattle—A scoping review.
      ). This may be useful to develop or test ethological theories, such as those relating to transitive inference (an individual inferring their likelihood of success in an unknown interaction based on observed interactions between groupmates;
      • Hobson E.A.
      • DeDeo S.
      Social feedback and the emergence of rank in animal society.
      ), winner and loser effects (
      • Landau H.G.
      On dominance relations and the structure of animal societies: I. Effect of inherent characteristics.
      ), and the relationship between dominance and cognition (e.g.,
      • Milewski T.M.
      • Lee W.
      • Champagne F.A.
      • Curley J.P.
      Behavioral and physiological plasticity in social hierarchies.
      ). However, the effect of common dairy cattle management practices, such as sexual segregation, on social behavior is not clearly understood and should be considered when using dairy cattle as a model for social behavior research.

      Some Practical Applications of Dominance

      Measuring dominance may be valuable for understanding and mitigating some welfare concerns for group-housed cattle; however, methods of determining dominance may differ as to when they are best applied. For instance, temporally sensitive methods (e.g., Elo-rating) are likely ideal for observing how hierarchies develop after mixing or environmental change. Conversely, temporally robust methods (e.g., normalized David's score) may be best for determining how individual characteristics influence the attributes of a stable hierarchy. Further, recent work has highlighted the importance of the social environment and individual experience for welfare in animals (e.g.,
      • Winckler C.
      Assessing animal welfare at the farm level: Do we care sufficiently about the individual?.
      ); changes in social behavior have been suggested to coincide with welfare concerns in dairy cows (e.g.,
      • Neave H.W.
      • Lomb J.
      • Weary D.M.
      • LeBlanc S.J.
      • Huzzey J.M.
      • von Keyserlingk M.A.G.
      Behavioral changes before metritis diagnosis in dairy cows.
      ;
      • Foris B.
      • von Keyserlingk M.A.G.
      • Weary D.M.
      Competition strategies of metritic and healthy transition cows.
      ). Dominance is expected to be stable (
      • Finkemeier M.A.
      • Langbein J.
      • Puppe B.
      Personality research in mammalian farm animals: Concepts, measures, and relationship to welfare.
      ); therefore, longitudinal and temporally sensitive methods for monitoring changes in dominance may be useful for the early identification of compromised welfare. Moreover, subordinate cows may be particularly vulnerable (
      • Estevez I.
      • Andersen I.L.
      • Nævdal E.
      Group size, density, and social dynamics in farm animals.
      ;
      • Foris B.
      • Lecorps B.
      • Krahn J.
      • Weary D.M.
      • von Keyserlingk M.A.G.
      The effects of cow dominance on the use of a mechanical brush.
      ), as they regularly receive agonistic interactions and may be frequently unable to access resources at optimal times or locations (e.g.,
      • Val-Laillet D.
      • Passillé A.M.
      • Rushen J.
      • von Keyserlingk M.A.G.
      The concept of social dominance and the social distribution of feeding-related displacements between cows.
      ). Temporally robust methods of calculating dominance are likely best for identifying cows that are consistently subordinate, enabling better monitoring and more timely intervention in welfare concerns.

      Some Limitations of Dominance

      Dominance does not encapsulate an individual's entire social experience and is limited when determined using only agonistic interactions. For example, dominance relationships may vary in their association with affiliative behaviors (e.g.,
      • Foris B.
      • Zebunke M.
      • Langbein J.
      • Melzer N.
      Comprehensive analysis of affiliative and agonistic social networks in lactating dairy cattle groups.
      ), leadership (e.g.,
      • Papageorgiou D.
      • Farine D.R.
      Shared decision-making allows subordinates to lead when dominants monopolize resources.
      ), familiarity (e.g.,
      • Gutmann A.K.
      • Špinka M.
      • Winckler C.
      Long-term familiarity creates preferred social partners in dairy cows.
      ), social leverage (i.e., control of resources not achievable by force;
      • Lewis R.J.
      Aggression, rank, and power: Why hens (and other animals) do not always peck according to their strength.
      ), and personality traits (e.g.,
      • Réale D.
      • Reader S.M.
      • Sol D.
      • McDougall P.T.
      • Dingemanse N.J.
      Integrating animal temperament within ecology and evolution.
      ). Subjectivity may be present when identifying the intention or outcome of behaviors (e.g., affiliative or agonistic, win or loss;
      • Wemelsfelder F.
      The scientific validity of subjective concepts in models of animal welfare.
      ), which may limit the reliability of measurements for dominance calculations. Moreover, estimating dominance often includes the categorization of continuous information. These categorizations occur when collecting data (e.g., definition of agonistic interaction), calculating scores, ranking, and assigning rank or dyad-associated titles (e.g., dominant or subordinate). Each categorization increases overall measurement uncertainty (
      • van Walraven C.
      • Hart R.G.
      Leave 'em alone—Why continuous variables should be analyzed as such.
      ), increasing the risk of generating unreliable dominance estimates that poorly represent the social dynamics.

      CONCLUSIONS

      Dominance is an aspect of the social experience of cattle, the effect of which is likely to vary depending upon social and environmental context. The methods used to determine dominance have implications for how dominance is represented. Following a standardized approach for estimating dominance in cattle may be beneficial for future research.

      ACKNOWLEDGMENTS

      This research has been funded, in part, by a Natural Science and Engineering Research Council (NSERC; Ottawa, ON, Canada) Discovery Grant RGPIN-2021-02848 awarded to MvK. JK was funded by a NSERC postgraduate masters scholarship. General funding for the UBC Animal Welfare program comes from the NSERC Industrial Research Chair awarded to MvK and DMW with industry contributions from Dairy Farmers of Canada (Ottawa, ON, Canada), Alberta Milk (Edmonton, AB, Canada), Saputo (Montreal, QC, Canada), British Columbia Dairy Association (Burnaby, BC, Canada), Merck (Kirkland, QC, Canada), British Columbia Cattle Industry Development Fund (Kamloops, BC, Canada), Boehringer Ingelheim (Burlington, ON, Canada), Semex Alliance (Guelph, ON, Canada), Lactanet (Sainte-Anne-de-Bellevue, QC, Canada), Dairy Farmers of Manitoba (Winnipeg, MB, Canada), and SaskMilk (Regina, SK, Canada). We thank Sky Sheng (University of British Columbia, Vancouver, Canada) and Claire Lloyd (Vancouver, Canada) for helpful comments on an earlier draft of this paper. The authors have not stated any conflicts of interest.

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