Reaching reproduction in a large carnivore: Role of early environment and intrinsic traits

To reach reproduction, individuals must survive the juvenile stage, a critical period of low survival rates in large carnivores. Early-life conditions during this stage can have lasting effects on survival, reproductive maturation, growth, physiology, and behaviour. We assessed recruitment probability in Scandinavian wolves, i.e., the probability that a wolf to reaches the reproductive stage and has pups surviving at least five months of age. To unravel human-related and biological factors within the natal territory that could affect recruitment probability, we analysed life-history data from 582 Scandinavian wolves (Canis lupus) identified by DNA as pups or juveniles in their birth territory. Factors considered included main prey density, road density, human density, and proximity to non-breeding zones, as well as sex, inbreeding level and collaring. Among the 582 wolves analysed, 122 produced at least one surviving pup, corresponding to a recruitment probability of 0.21. Recruitment probability was more than twice as high (0.5) for juvenile wolves fitted with GPS collars compared to non-collared individuals (0.22), and was positively correlated with human population density in the natal territory. We found no significant effects of other biologically or human-related predictors. These results suggest that in this large carnivore population, managed below carrying capacity, individual recruitment probability is primarily influenced by human-related factors, potentially reflecting poaching risk.

个体若要实现繁殖，需顺利度过幼年期——这是大型食肉动物中存活率普遍偏低的关键生命阶段。该阶段的早期生活环境，会对个体的存活率、繁殖成熟度、生长发育、生理机能与行为模式产生持久影响。本研究针对斯堪的纳维亚灰狼评估了其繁殖招募概率，即灰狼个体达到繁殖阶段且其幼崽至少存活5个月的概率。为厘清出生领地内可能影响繁殖招募概率的人为与生物相关因素，我们分析了582只斯堪的纳维亚灰狼（Canis lupus）的生命史数据——这些个体均通过DNA鉴定确认为其出生领地内的幼崽或亚成体。本次研究考量的影响因子包括主要猎物密度、道路密度、人口密度、距非繁殖区的距离，以及个体性别、近交水平与项圈佩戴情况。在被分析的582只灰狼中，共有122只成功产下至少1只存活幼崽，繁殖招募概率为0.21。佩戴GPS项圈的亚成体灰狼，其繁殖招募概率（0.5）约为未佩戴项圈个体（0.22）的两倍以上，且与出生领地内的人口密度呈正相关。其余生物或人为相关预测因子未产生显著影响。本研究结果表明，在这一处于承载量以下的受管理大型食肉动物种群中，个体繁殖招募概率主要受人为因素影响，这可能反映了盗猎风险的作用。