Replication data for: Redefining dominance calculation: Increased competition flattens the dominance hierarchy in dairy cows

Dominance hierarchies are known for mitigating conflicts and guiding priority of access to limited resources in gregarious animals. The dominance hierarchy of dairy cows is typically constructed using agonistic interactions, usually monitored at the feed bunk right after fresh feed delivery when competition is high resulting in numerous interactions. Yet, the outcome of agonistic interactions under time of high competition time may be more influenced by cows’ high valuation of fresh feed than their intrinsic dominance attributes. Thus, the dominance hierarchy constructed using agonistic interactions under high versus low competition times might differ. The aim of this study was to test how the structure of the dominance hierarchy changes in relation to different levels of competition. We monitored a dynamically changing group of 48 lactating dairy cows over 10 mo with 6 cows exchanged every 16 d, totally 159 cows. We used a validated algorithm to continuously detect the actor and reactor of replacement behaviors as cows competed for feed. We calculated feeder occupancy, the percentage of occupied feed bins, to characterize competition at the moment of each replacement, and created 25 corresponding dominance hierarchies using Elo ratings for occupancy levels ranging from 13% to 100%. With each 10% rise in feeder occupancy, hierarchy steepness fell by 0.02 (R2 = 0.96) and two-way dyads rose by 1.3% (R2 = 0.84). The win rate of the dominant cow within dyads declined with increased feeder occupancy (y = -0.11x -0.21, P < 0.001). Our findings provide evidence that there is noticeable variation in inferred hierarchies based on the competition context, with high competition flattening the hierarchy as subordinate animals succeed more in replacing others in order to gain feed access. This finding underscores that during heightened competition, the valuation of resources impacts agonistic behaviors and the subsequently constructed dominance hierarchy more than the individual's intrinsic dominance attributes. We recommend that researchers avoid using agonistic interactions occurring immediately after fresh feed delivery to establish dominance hierarchies. We also urge researchers to differentiate agonistic interactions based on context when constructing dominance hierarchies to draw inferences on animal behavior, cognition and health.

群居动物的优势等级（dominance hierarchy）系统以缓解群体冲突、规范有限资源的获取优先级而广受认可。奶牛的优势等级通常通过争斗性互动（agonistic interactions）构建，这类互动多在新鲜饲料投放后即刻于饲槽处监测——此时竞争烈度较高，互动频次亦随之攀升。然而，高竞争场景下的争斗性互动结果，受奶牛对新鲜饲料的价值评估影响，或许甚于其自身固有优势等级属性。因此，基于高、低竞争场景下的争斗性互动所构建的优势等级，或存在差异。

本研究旨在探究优势等级结构随竞争水平变化的规律。我们对由48头泌乳奶牛组成的动态群体开展了为期10个月的监测：每16天更换6头奶牛，累计纳入159头受试个体。我们采用经验证的算法，持续识别奶牛在抢食过程中发起替换行为的施动者与受动者。我们通过计算饲槽占用率（feeder occupancy，即已使用饲槽占总饲槽的百分比）来表征单次替换发生时的竞争烈度，并针对13%至100%的饲槽占用水平区间，基于Elo评分（Elo ratings）构建了25组对应的优势等级体系。饲槽占用率每提升10%，优势等级的陡峭程度下降0.02（决定系数R²=0.96），双向互动配对占比上升1.3%（R²=0.84）。配对中优势个体的获胜率随饲槽占用率升高而降低（拟合方程：y = -0.11x - 0.21，P < 0.001）。

本研究结果证实，基于不同竞争场景推导得到的优势等级存在显著差异：高竞争场景下，从属个体更易成功替换同类以获取饲料，进而使等级结构趋于平缓。该结果进一步凸显，在竞争加剧时，个体对资源的价值评估对争斗性行为及后续构建的优势等级的影响，甚于其自身固有优势等级属性。我们建议研究者避免利用新鲜饲料投放后即刻发生的争斗性互动来构建优势等级。同时，我们呼吁研究者在构建优势等级以推导动物行为、认知与健康相关结论时，需根据场景对争斗性互动进行区分。