Animal Health Department, Veterinary Faculty, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, 30100 Espinardo, Murcia, Spain; Island Ecology and Evolution Research Group (IPNA-CSIC), Astrofísico Francisco Sánchez 3, 38206 La Laguna, Tenerife, Canary Islands, Spain; Portuguese Society for the Study of Birds, Avenida João Crisóstomo, 18-4°Dto, 1000-179 Lisboa, Portugal.
Marine and Environmental Research Center (IMAR/CMA), Department of Life Sciences, University of Coimbra, Apartado 3046, 3001-401 Coimbra, Portugal.
Zoology (Jena). 2014 Jun;117(3):171-8. doi: 10.1016/j.zool.2013.12.003. Epub 2014 Mar 4.
This study assessed the impact of introduced black rats (Rattus rattus) on Cory's shearwater (Calonectris diomedea borealis) in a multi-invaded insular ecosystem where rats are mesopredators. We hypothesized that black rats should have little impact on Cory's shearwaters in the presence of cats as superpredators. Stomach contents and stable isotope analysis (SIA) in tissues of black rats were analyzed to assess the trophic ecology and the importance of Cory's shearwater in their diet. We also studied the isotopic signature in tissues of house mouse (Mus domesticus) to confirm previous data showing no predation of this species on Cory's shearwaters. For both rodent species, temporal variation in diet composition in response to the availability of seabird prey was evaluated, and short- and long-term consistency in diet was tested using different tissues from the same individual. For black rats a Bayesian isotope mixing model (SIAR) was applied to determine the relative contribution of each prey to the individual diet. SIA of mouse tissues varied between the Cory's shearwater breeding and non-breeding periods. However, no significant differences were found in diet and SIA for black rats. In contrast, individuals of both species showed a strong consistency in diet which apparently benefited their body condition index. Although black rats supplement their diet with Cory's shearwater eggs and chicks (8.3% in stomach contents and 10.6% in the SIAR model), their current impact on the Cory's shearwater population appears to be small, probably due to several factors including the small size of the rat population and a high level of rat predation by cats.
本研究评估了引入的黑鼠（Rattus rattus）对多入侵岛屿生态系统中冠毛小海雀（Calonectris diomedea borealis）的影响，在该生态系统中，老鼠是中型捕食者。我们假设，在有超级捕食者猫存在的情况下，黑鼠对冠毛小海雀的影响应该很小。我们分析了黑鼠的胃内容物和组织中的稳定同位素分析（SIA），以评估其营养生态学以及冠毛小海雀在其饮食中的重要性。我们还研究了家鼠（Mus domesticus）组织中的同位素特征，以证实先前的数据表明该物种不会捕食冠毛小海雀。对于这两种啮齿动物，我们评估了饮食组成随海鸟猎物可利用性的时间变化，并使用来自同一个体的不同组织测试了短期和长期饮食的一致性。对于黑鼠，我们应用贝叶斯同位素混合模型（SIAR）来确定每种猎物对个体饮食的相对贡献。在冠毛小海雀繁殖和非繁殖期间，老鼠组织的 SIA 发生了变化。然而，黑鼠的饮食和 SIA 没有发现显著差异。相比之下，这两种物种的个体饮食表现出很强的一致性，这显然有利于它们的身体状况指数。尽管黑鼠补充了以冠毛小海雀的蛋和雏鸟为食（胃内容物中为 8.3%，SIAR 模型中为 10.6%），但它们对冠毛小海雀种群的当前影响似乎很小，可能是由于几个因素，包括老鼠种群的规模较小和猫对老鼠的高捕食率。
