Max Planck Institute for Ornithology, Vogelwarte Radolfzell, Radolfzell, Germany.
PLoS One. 2013 Jul 2;8(7):e67714. doi: 10.1371/journal.pone.0067714. Print 2013.
Many animals show some degree of individual specialization in foraging strategies and diet. This has profound ecological and evolutionary implications. For example, populations containing diverse individual foraging strategies will respond in different ways to changes in the environment, thus affecting the capacity of the populations to adapt to environmental changes and to diversify. However, patterns of individual specialization have been examined in few species. Likewise it is usually unknown whether specialization is maintained over time, because examining the temporal scale at which specialization occurs can prove difficult in the field. In the present study, we analyzed individual specialization in foraging in Dolphin Gulls Leucophaeus scoresbii, a scavenger endemic to the southernmost coasts of South America. We used GPS position logging and stable isotope analyses (SIA) to investigate individual specialization in feeding strategies and their persistence over time. The analysis of GPS data indicated two major foraging strategies in Dolphin Gulls from New I. (Falkland Is./Islas Malvinas). Tagged individuals repeatedly attended either a site with mussel beds or seabird and seal colonies during 5 to 7 days of tracking. Females foraging at mussel beds were heavier than those foraging at seabird colonies. Nitrogen isotope ratios (δ(15)N) of Dolphin Gull blood cells clustered in two groups, showing that individuals were consistent in their preferred foraging strategies over a period of at least several weeks. The results of the SIA as well as the foraging patterns recorded revealed a high degree of specialization for particular feeding sites and diets by individual Dolphin Gulls. Individual differences in foraging behavior were not related to sex. Specialization in Dolphin Gulls may be favored by the advantages of learning and memorizing optimal feeding locations and behaviors. Specialized individuals may reduce search and handling time and thus, optimize their energy gain and/or minimize time spent foraging.
许多动物在觅食策略和饮食上表现出一定程度的个体特化。这具有深远的生态和进化意义。例如，包含不同个体觅食策略的种群将以不同的方式对环境变化做出反应，从而影响种群适应环境变化和多样化的能力。然而，个体特化的模式在少数物种中得到了研究。同样，通常不知道特化是否随着时间的推移而保持，因为在现场检查特化发生的时间尺度可能会很困难。在本研究中，我们分析了南美的最南端海岸特有的一种食腐动物——海豚鸥（Leucophaeus scoresbii）的觅食个体特化。我们使用 GPS 位置记录和稳定同位素分析（SIA）来研究觅食策略的个体特化及其随时间的持久性。GPS 数据分析表明，来自新岛（福克兰群岛/马尔维纳斯群岛）的海豚鸥有两种主要的觅食策略。被标记的个体在追踪的 5 到 7 天内反复出现在贻贝床或海鸟和海豹聚居地的一个地点。在贻贝床上觅食的雌性比在海鸟聚居地觅食的雌性更重。海豚鸥血细胞的氮同位素比值（δ(15)N）聚类成两组，表明个体在至少数周的时间内保持其偏好的觅食策略。SIA 的结果以及记录的觅食模式表明，个体对特定的觅食地点和饮食表现出高度的特化。觅食行为的个体差异与性别无关。海豚鸥的特化可能受益于学习和记忆最佳觅食地点和行为的优势。专业化个体可能会减少搜索和处理时间，从而优化其能量收益和/或减少觅食时间。
