Data from: Let’s stay together? Intrinsic and extrinsic factors involved in pair bond dissolution in a recolonizing wolf population

For socially monogamous species, breeder bond dissolution has important consequences for population dynamics, but the extent to which extrinsic or intrinsic population factors causes pair dissolution remain poorly understood, especially among carnivores.
Using an extensive life-history data set, a survival analysis and competing risks framework, we examined the fate of 153 different wolf (Canis lupus) pairs in the recolonizing Scandinavian wolf population, during 14 winters of snow tracking and DNA monitoring.
Wolf pair dissolution was generally linked to a mortality event and was strongly affected by extrinsic (i.e. anthropogenic) causes. No divorce was observed, and among the pair dissolution where causes have been identified, death of one or both wolves was always involved. Median time from pair formation to pair dissolution was three consecutive winters (i.e. approximately 2 years). Pair dissolution was mostly human-related, primarily caused by legal control actions (36·7%), verified poaching (9·2%) and traffic-related causes (2·1%). Intrinsic factors, such as disease and age, accounted for only 7·7% of pair dissolutions. The remaining 44·3% of dissolution events were from unknown causes, but we argue that a large portion could be explained by an additional source of human-caused mortality, cryptic poaching.
Extrinsic population factors, such as variables describing the geographical location of the pair, had a stronger effect on risk of pair dissolution compared to anthropogenic landscape characteristics. Population intrinsic factors, such as the inbreeding coefficient of the male pair member, had a negative effect on pair bond duration. The mechanism behind this result remains unknown, but might be explained by lower survival of inbred males or more complex inbreeding effects mediated by behaviour.
Our study provides quantitative estimates of breeder bond duration in a social carnivore and highlights the effect of extrinsic (i.e. anthropogenic) and intrinsic factors (i.e. inbreeding) involved in wolf pair bond duration. Unlike the effects of intrinsic and extrinsic factors that are commonly reported on individual survival or population growth, here we provide quantitative estimates of their potential effect on the social unit of the population, the wolf pair.

对于社会一夫一妻制（socially monogamous）物种而言，繁殖配偶关系解体对种群动态具有重要影响，但外在或内在种群因素在多大程度上引发配偶对解体，目前仍知之甚少，针对食肉动物类群的相关研究尤为匮乏。
本研究依托大规模生活史数据集（life-history data set），结合生存分析（survival analysis）与竞争风险框架（competing risks framework），对历时14个冬季的雪地追踪与DNA监测数据展开分析，考察了种群重建中的斯堪的纳维亚灰狼（Canis lupus）种群中153个独立灰狼配偶对的存续结局。
灰狼配偶对的解体通常与死亡事件相关，且显著受外在（即人为）因素影响。本研究未观察到主动离异现象，在已明确解体原因的案例中，均涉及一方或双方灰狼的死亡。从配偶形成到解体的中位时长为连续3个冬季（约合2年）。配偶对解体大多与人类活动相关，主要诱因为合法管控捕杀（36.7%）、经核实的偷猎（9.2%）以及交通事故相关致死（2.1%）。内在因素如疾病与年龄仅解释了7.7%的配偶解体事件。剩余44.3%的解体事件原因不明，但我们认为其中很大一部分可归因于另一类人为致死源——隐蔽偷猎（cryptic poaching）。
外在种群因素（如描述配偶对地理位置的变量）对配偶解体风险的影响，要强于人为景观特征。种群内在因素如雄性配偶个体的近交系数（inbreeding coefficient），对配偶关系存续时长具有负向影响。该结果背后的机制尚不清楚，但可能源于近交雄性的存活率更低，或是由行为介导的更为复杂的近交效应。
本研究为社会食肉动物的繁殖配偶关系存续时长提供了量化估计，并阐明了外在（即人为）与内在（即近交）因素对灰狼配偶关系存续时长的作用。与以往常见的针对个体存活或种群增长的内在、外在因素效应研究不同，本研究针对种群的社会单元——灰狼配偶对，量化评估了这些因素的潜在影响。