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Evaluating different spatial scales of forage item availability to determine diet selection of juvenile green turtles (Chelonia mydas)
Marine Biology ( IF 2.4 ) Pub Date : 2020-10-22 , DOI: 10.1007/s00227-020-03782-y
Anthony J. Gillis , Natalie E. Wildermann , Simona A. Ceriani , Jeffrey A. Seminoff , Mariana M. P. B. Fuentes

Diet selection by a species is determined by comparing the consumption (i.e., use) and abundance (i.e., availability) of prey within their area of occupancy. Because individuals commonly use only a portion of habitat available to them (e.g., a 10-ha home range within a 1000-ha foraging habitat), it is important to quantify forage availability within individuals’ home ranges and core areas, and include these availabilities when calculating diet selection. However, studies of diet selection often consider prey availability across the entire foraging habitat of a species and not within individual home ranges/core areas. Here, we explore how spatial variability in prey availability may influence the results of diet selection for juvenile green turtles, Chelonia mydas, foraging in Bimini, Bahamas. Stable isotope analysis was used to determine prey use and satellite telemetry to infer movements and forage availability for each turtle. Forage availability was assessed at three spatial scales: (1) the full extent of the foraging area (2) across each respective individual’s 95% utilization distribution (UD), or home ranges, and (3) across each individual’s 50% UD, or core areas. Further, we compared potential differences in diet selection by using three selection indices (Ivlev’s, Johnson’s and Chesson’s). Diet selection results varied among individuals and were influenced by the spatial scale of forage items available and the index used. Diet selection variability was observed at various spatial scales and in all indices. Our results highlight the need for careful consideration of the diet selection index and the spatial scale at which prey/forage availability is considered when determining a species’ diet selection. Selecting a more sensitive index will help identify priority resources and/or habitats that are important to species, which in turn carries conservation and management implications.

中文翻译:

评估草料项目可用性的不同空间尺度以确定幼年绿海龟(Chelonia mydas)的饮食选择

一个物种的饮食选择是通过比较其居住区域内猎物的消耗(即使用)和丰度(即可用性)来确定的。由于个体通常只使用他们可用栖息地的一部分(例如,1000 公顷觅食栖息地内的 10 公顷家庭范围),因此量化个人家庭范围和核心区域内的草料可用性非常重要,并包括这些可用性在计算饮食选择时。然而,饮食选择研究通常会考虑整个物种觅食栖息地的猎物可用性,而不是在单个家庭范围/核心区域内。在这里,我们探讨了猎物可用性的空间变异性如何影响在巴哈马比米尼岛觅食的幼年绿海龟 Chelonia mydas 的饮食选择结果。稳定同位素分析用于确定猎物的使用和卫星遥测,以推断每只海龟的运动和草料可用性。在三个空间尺度上评估草料可用性:(1) 觅食区的全部范围 (2) 跨越每个个体的 95% 利用率分布 (UD) 或家庭范围,以及 (3) 跨越每个个体的 50% UD,或核心领域。此外,我们通过使用三个选择指数(Ivlev's、Johnson's 和 Chesson's)比较了饮食选择的潜在差异。饮食选择结果因人而异,并受可用草料项目的空间尺度和所用指数的影响。在不同的空间尺度和所有指数中观察到饮食选择的变异性。我们的结果强调了在确定物种的饮食选择时需要仔细考虑饮食选择指数和考虑猎物/草料可用性的空间尺度。选择一个更敏感的指数将有助于确定对物种很重要的优先资源和/或栖息地,这反过来又会带来保护和管理的影响。
更新日期:2020-10-22
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