Department of Environmental Biology, Sapienza University of Rome, Rome, Italy.
Department of Biology and Biotechnologies "Charles Darwin", Sapienza University of Rome, Rome, Italy.
Sci Rep. 2021 Jul 8;11(1):14118. doi: 10.1038/s41598-021-93507-y.
Apennine brown bears (Ursus arctos marsicanus) survive in an isolated and critically endangered population, and their food habits have been studied using traditional scat analysis. To complement current dietary knowledge, we applied Stable Isotope Analysis (SIA) to non-invasively collected bear hairs that had been individually recognized through multilocus genotyping. We analysed carbon (δC) and nitrogen (δN) stable isotopes of hair sections and bear key foods in a Bayesian mixing models framework to reconstruct the assimilated diet on a seasonal basis and to assess gender and management status effects. In total, we analysed 34 different seasonal bear key foods and 35 hair samples belonging to 27 different bears (16 females and 11 males) collected during a population survey in 2014. Most bears showed wide δN and δC ranges and individual differences in seasonal isotopic patterns. Vegetable matter (herbs, fleshy fruits and hard mast) represented the major component of the assimilated diet across the dietary seasons, whereas vegetable crops were rarely and C4 plants (i.e., corn) never consumed. We confirmed an overall low consumption of large mammals by Apennine bears consistently between sexes, with highest values in spring followed by early summer but null in the other seasons. We also confirmed that consumption of fleshy fruits peaked in late summer, when wild predominated over cultivated fleshy fruits, even though the latter tended to be consumed in higher proportion in autumn. Male bears had higher δ N values than females in spring and autumn. Our findings also hint at additional differences in the assimilated diet between sexes, with females likely consuming more herbs during spring, ants during early summer, and hard mast during fall compared to males. In addition, although effect sizes were small and credibility intervals overlapped considerably, management bears on average were 0.9‰ lower in δ C and 2.9‰ higher in δ N compared to non-management bears, with differences in isotopic values between the two bear categories peaking in autumn. While non-management bears consumed more herbs, wild fleshy fruits, and hard mast, management bears tended to consume higher proportions of cultivated fruits, ants, and large mammals, possibly including livestock. Although multi-year sampling and larger sample sizes are needed to support our findings, our application confirms that SIA can effectively integrate previous knowledge and be efficiently conducted using samples non-invasively collected during population surveys.
亚平宁棕熊（Ursus arctos marsicanus）生活在一个孤立且岌岌可危的种群中，其食性已通过传统的粪便分析进行了研究。为了补充当前的饮食知识，我们应用稳定同位素分析（SIA）对通过多基因座基因型鉴定进行个体识别的熊毛进行了分析。我们在贝叶斯混合模型框架中分析了毛发部分的碳（δC）和氮（δN）稳定同位素以及熊的关键食物，以在季节性基础上重建同化饮食，并评估性别和管理状态的影响。总共，我们分析了 2014 年种群调查中收集的 34 种不同季节性熊关键食物和 35 个毛发样本，这些毛发样本属于 27 只不同的熊（16 只雌性和 11 只雄性）。大多数熊表现出广泛的 δN 和 δC 范围以及季节性同位素模式的个体差异。植物物质（草本植物、肉质水果和硬木）是整个饮食季节中同化饮食的主要成分，而蔬菜作物很少被食用，C4 植物（即玉米）从未被食用过。我们确认，亚平宁棕熊的大型哺乳动物总体摄入量在两性之间一直较低，春季最高，其次是初夏，但其他季节则为零。我们还确认，肉质水果的摄入量在夏末达到峰值，此时野生肉质水果超过了栽培肉质水果，尽管后者在秋季的摄入量比例更高。雄性熊在春季和秋季的 δN 值高于雌性熊。我们的研究结果还暗示了两性之间在同化饮食方面的其他差异，与雄性熊相比，雌性熊在春季可能更多地食用草本植物，在初夏食用蚂蚁，在秋季食用硬木。此外，尽管效应大小较小，置信区间重叠较大，但与非管理熊相比，管理熊的 δC 平均低 0.9‰，δN 高 2.9‰，两个熊类之间的同位素值差异在秋季达到峰值。虽然需要多年的采样和更大的样本量来支持我们的发现，但我们的应用证实，SIA 可以有效地整合先前的知识，并使用在种群调查中非侵入性收集的样本进行有效地进行。
