Baylis A M M, Orben R A, Arnould J P Y, Peters K, Knox T, Costa D P, Staniland I J
Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Warrnambool, 3280, Australia.
South Atlantic Environmental Research Institute, Stanley, FIQQ1ZZ, Falkland Islands.
Oecologia. 2015 Dec;179(4):1053-65. doi: 10.1007/s00442-015-3421-4. Epub 2015 Sep 1.
Despite global declines in the abundance of marine predators, knowledge of foraging ecology, necessary to predict the ecological consequences of large changes in marine predator abundance, remains enigmatic for many species. Given that populations suffering severe declines are of conservation concern, we examined the foraging ecology of southern sea lions (SSL) (Otaria flavescens)-one of the least studied otariids (fur seal and sea lions)-which have declined by over 90% at the Falkland Islands since the 1930s. Using a combination of biologging devices and stable isotope analysis of vibrissae, we redress major gaps in the knowledge of SSL ecology and quantify patterns of individual specialization. Specifically, we revealed two discrete foraging strategies, these being inshore (coastal) and offshore (outer Patagonian Shelf). The majority of adult female SSL (72% or n = 21 of 29 SSL) foraged offshore. Adult female SSL that foraged offshore travelled further (92 ± 20 vs. 10 ± 4 km) and dived deeper (75 ± 23 vs. 21 ± 8 m) when compared to those that foraged inshore. Stable isotope analysis revealed long-term fidelity (years) to these discrete foraging habitats. In addition, we found further specialization within the offshore group, with adult female SSL separated into two clusters on the basis of benthic or mixed (benthic and pelagic) dive behavior (benthic dive proportion was 76 ± 9 vs. 51 ± 8%, respectively). We suggest that foraging specialization in depleted populations such as SSL breeding at the Falkland Islands, are influenced by foraging site fidelity, and could be independent of intraspecific competition. Finally, the behavioral differences we describe are crucial to understanding population-level dynamics, impediments to population recovery, and threats to population persistence.
尽管全球海洋食肉动物的数量在下降，但对于许多物种来说，预测海洋食肉动物数量大幅变化的生态后果所必需的觅食生态学知识仍然是个谜。鉴于遭受严重数量下降的种群受到保护关注，我们研究了南海狮（Otaria flavescens）的觅食生态学，南海狮是研究最少的海狗科动物（海狗和海狮）之一，自20世纪30年代以来，其数量在福克兰群岛下降了90%以上。我们结合使用生物记录设备和触须的稳定同位素分析，弥补了南海狮生态学知识的主要空白，并量化了个体专业化模式。具体来说，我们揭示了两种不同的觅食策略，即近岸（沿海）和离岸（巴塔哥尼亚大陆架外缘）。大多数成年雌性南海狮（72%，即29只南海狮中的21只）在离岸处觅食。与在近岸觅食的成年雌性南海狮相比，在离岸处觅食的成年雌性南海狮游动得更远（分别为92±20公里和10±4公里），潜水更深（分别为75±23米和21±8米）。稳定同位素分析显示，它们对这些不同的觅食栖息地具有长期（数年）忠诚度。此外，我们发现离岸群体内部存在进一步的专业化，成年雌性南海狮根据底栖或混合（底栖和中上层）潜水行为分为两个集群（底栖潜水比例分别为76±9%和51±8%）。我们认为，在福克兰群岛繁殖的南海狮等数量减少的种群中的觅食专业化受到觅食地点忠诚度的影响，并且可能与种内竞争无关。最后，我们描述的行为差异对于理解种群水平的动态、种群恢复的障碍以及种群持续存在的威胁至关重要。
