Introduced black rats Rattus rattus on Ile de la Possession (Iles Crozet, Subantarctic): diet and trophic position in food webs.

• Published in: Polar Biology
• Main Authors: Pisanu, Benoit, Caut, Stephane, Gutjahr, Sylvain, Vernon, Philippe, Chapuis, Jean Louis
• Other Authors: Centre d'Ecologie et des Sciences de la COnservation (CESCO), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centro de Investigaciones Biológicas (CSIC), Consejo Superior de Investigaciones Cientificas = Spanish National Research Council (CSIC), Ecosystèmes, biodiversité, évolution Rennes (ECOBIO), Université de Rennes (UR)-Institut Ecologie et Environnement - CNRS Ecologie et Environnement (INEE-CNRS), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), IPEV 136 Ecobio CNRS ZA Antarctique et Subantarctique CSIC, ANR-05-BDIV-0003,ALIENS,Assessment and Limitation of the Impacts of Exotic species in Nationwide insular Systems(2005)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: Stable isotopes; Food web; Subantarctic island; Introduced rodent; Rattus rattus; Diet; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Polar Biology
• Online Access: https://hal.science/hal-00597309; https://doi.org/10.1007/s00300-010-0867-z

International audience Rats introduced on islands can affect ecosystem structure and function by feeding on terrestrial plants and both marine and terrestrial animals. The diet and trophic position of Rattus rattus introduced on Ile de la Possession (Iles Crozet) was assessed from two sites, according to the presence or absence of a king penguin colony. We used three complementary assays: macroanalyses of the stomach, faecal microhistology, and stable isotope analyses of d15N/d13C in liver. Near the rookery, spermatophytes contributed on average 50% (confidential interval: 23-75) to the diet based on isotopes, mainly consisting in reproductive parts of Poa spp., Agrostis magellanica, and Cerastium fontanum identified in faeces. Terrestrial animal preys were represented by insects that contributed 25% (0-56) in isotopes, dominated in faeces by caterpillars of Pringleophaga spp. and adult weevils. Bird remains were found in faeces, forming 18% (6-30) of isotopes. Terrestrial earthworms contributed to 7% (0-21), with chaetae observed in faeces. On the other site, spermatophytes represented 62% (51-73) of assimilated food in rats' livers, mainly formed by Poaceae and Acaena magellanica, insects by caterpillars [24% (10-39)], and terrestrial earthworms [13% (2-23)]. Our results suggest that rats, which were found at the top of terrestrial food chains, may have a direct role on a such simplified ecosystem, by preying on the most abundant and largest body-sized terrestrial invertebrates,--e.g. the keystone species Pringleophaga spp.--, and by feeding on both reproductive and vegetative parts of autochthonous and introduced plants. The discrepancies and usefulness of employing both isotopes and faecal analyses are discussed.