Páez-Rosas Diego, Villegas-Amtmann Stella, Costa Daniel
Universidad San Francisco de Quito (USFQ) and Galapagos Science Center, Galápagos, Ecuador.
Dirección Parque Nacional Galápagos, Unidad Técnica Operativa San Cristóbal, Galápagos, Ecuador.
PLoS One. 2017 Oct 23;12(10):e0185165. doi: 10.1371/journal.pone.0185165. eCollection 2017.
The trophic behavior of marine predators varies according to the level of competition to which they are exposed. In general, populations that inhabit lower productivity systems face a strong intraspecific competition, which contributes to the development of different foraging strategies to maximize nutritional efficiency. Given the high trophic flexibility of Zalophus wollebaeki, this species is considered appropriate for the analysis of such behavior. Furthermore, this trophic flexibility has allowed them to persist in a seemingly marginal ecosystem. In this study, we used a comparative analysis of variables (diet and dive behavior) related to Z. wollebaeki trophic niche plasticity to better understand their foraging ecology, using techniques such scat analysis, satellite telemetry and complementarily an isotopic analysis. Scat analysis revealed intra-population variation in their diet, represented by prey from different environments (epipelagic and benthic). These results are supported by the animals' locations at sea and diving profiles. Global Positioning System (GPS) and time-depth recorder (TDR) records showed the existence of two groups, with differing feeding areas and diving behavior. Also the δ15N values showed differences in the trophic level at which the species fed. These results constitute a relevant finding in the evolutionary behavior of the species, showing that Z. wollebaeki has developed a high degree of foraging flexibility, thus increasing its survival rate in an ecosystem that is highly demanding in terms of resource availability.
海洋捕食者的营养行为会根据它们所面临的竞争程度而有所不同。一般来说，栖息在生产力较低系统中的种群面临着激烈的种内竞争，这促使它们发展出不同的觅食策略，以最大限度地提高营养效率。鉴于北海狗（Zalophus wollebaeki）具有高度的营养灵活性，该物种被认为适合用于分析此类行为。此外，这种营养灵活性使它们能够在一个看似边缘的生态系统中生存下来。在本研究中，我们对与北海狗营养生态位可塑性相关的变量（饮食和潜水行为）进行了比较分析，以更好地了解它们的觅食生态学，采用了粪便分析、卫星遥测等技术，并辅以同位素分析。粪便分析揭示了其种群内部饮食的差异，表现为来自不同环境（上层和底层）的猎物。这些结果得到了动物在海上的位置和潜水剖面的支持。全球定位系统（GPS）和时间深度记录仪（TDR）记录显示存在两组，它们的觅食区域和潜水行为不同。此外，δ15N值也显示了该物种觅食营养级的差异。这些结果是该物种进化行为中的一项重要发现，表明北海狗已经发展出高度的觅食灵活性，从而在一个对资源可用性要求很高的生态系统中提高了其存活率。
