Nagel Rebecca, Stainfield Claire, Fox-Clarke Cameron, Toscani Camille, Forcada Jaume, Hoffman Joseph I
Department of Animal Behaviour, Bielefeld University, 33501 Bielefeld, Germany.
British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET, UK.
Proc Biol Sci. 2021 Mar 31;288(1947):20202882. doi: 10.1098/rspb.2020.2882. Epub 2021 Mar 24.
Allee effects play an important role in the dynamics of many populations and can increase the risk of local extinction. However, some authors have questioned the weight of evidence for Allee effects in wild populations. We therefore exploited a natural experiment provided by two adjacent breeding colonies of contrasting density to investigate the potential for Allee effects in an Antarctic fur seal () population that is declining in response to climate change-induced reductions in food availability. Biometric time-series data were collected from 25 pups per colony during two consecutive breeding seasons, the first of which was among the worst on record in terms of breeding female numbers, pup birth weights and foraging trip durations. In previous decades when population densities were higher, pup mortality was consistently negatively density dependent, with rates of trauma and starvation scaling positively with density. However, we found the opposite, with higher pup mortality at low density and the majority of deaths attributable to predation. In parallel, body condition was depressed at low density, particularly in the poor-quality season. Our findings shed light on Allee effects in wild populations and highlight a potential emerging role of predators in the ongoing decline of a pinniped species.
阿利效应在许多种群动态中起着重要作用，并会增加局部灭绝的风险。然而，一些作者质疑野生种群中阿利效应的证据权重。因此，我们利用了由两个密度不同的相邻繁殖群体提供的自然实验，来研究南极毛皮海狮种群中阿利效应的可能性，该种群正因气候变化导致食物供应减少而数量下降。在连续两个繁殖季节中，从每个群体的25只幼崽身上收集生物特征时间序列数据，其中第一个繁殖季节是有记录以来繁殖雌性数量、幼崽出生体重和觅食行程持续时间最差的季节之一。在过去几十年种群密度较高时，幼崽死亡率一直呈负密度依赖，创伤和饥饿发生率与密度呈正相关。然而，我们发现了相反的情况，低密度时幼崽死亡率更高，且大多数死亡归因于捕食。同时，低密度时身体状况较差，尤其是在质量较差的季节。我们的研究结果揭示了野生种群中的阿利效应，并突出了捕食者在鳍足类物种持续衰退中可能出现的新作用。
