Loggerhead sea turtles (Caretta caretta) occupy an array of marine habitats throughout their lives and understanding how this threatened species utilizes these habitats can help guide conservation efforts. This study used a combination of isotopic analysis (δ13C; δ15N) of turtle epidermis and epibiotic community composition to examine habitat-use patterns of nesting loggerheads from the South West Indian Ocean and related these to turtle body condition. First, we identified two foraging groups using relative changes in the turtle’s epidermis δ13C isotope values (of 170 individuals). Second, we show that epibiont communities (of 80 turtles) differed significantly between the two foraging groups, with oceanic/pelagic and neritic/benthic species occurring in higher abundances on turtles with depleted and enriched δ13C values, respectively. The complementary evidence from isotope and epibiont data thus indicates that nesting loggerheads of this population exhibit a bimodal foraging strategy. The relatively high variability in δ13C and δ15N values of the turtles’ tissue showed that they have a broad isotopic niche. While isotopic niches overlapped among turtles with different body conditions, very healthy individuals had a significantly narrower isotopic niche width than those in poorer condition. This suggests that turtles in very good condition are food specialists, and individuals with suboptimal body conditions utilise a wider range of food items and are more generalist foragers. These results show the value of using a combination of stable isotopes and epibiont communities as cost-effective tools that can be applied effectively to derive information on habitat-use patterns of migratory species.

中文翻译：

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稳定同位素和表皮生物群落揭示了在西南印度洋筑巢的红海龟的觅食栖息地

蠵海龟（Caretta caretta）一生占据一系列海洋栖息地，了解这种受威胁物种如何利用这些栖息地有助于指导保护工作。本研究结合了海龟表皮的同位素分析（δ13C；δ15N）和表生生物群落组成，研究了来自西南印度洋的筑巢蠵龟的栖息地使用模式，并将这些模式与海龟身体状况联系起来。首先，我们使用乌龟表皮 δ13C 同位素值（170 个个体）的相对变化确定了两个觅食组。其次，我们表明表生群落（80 只海龟）在两个觅食组之间存在显着差异，大洋/中上层和浅海/底栖物种分别出现在 δ13C 值耗尽和富集的海龟身上。因此，来自同位素和表观生物数据的补充证据表明，该种群的筑巢蠵龟表现出双峰觅食策略。海龟组织的 δ13C 和 δ15N 值相对较高的变异性表明它们具有广泛的同位素生态位。虽然身体状况不同的海龟之间的同位素生态位重叠，但非常健康的个体的同位素生态位宽度明显小于身体状况较差的个体。这表明状况良好的海龟是食物专家，而身体状况欠佳的个体则利用更广泛的食物，并且是更全面的觅食者。