Title Introduced black rats Rattus rattus on Ile de la Possession (Iles Crozet, subantarctic); diet and trophic position in food webs
Author Pisanu, B.; Caut, S.; Gutjahr, S.; Vernon, P.; Chapuis, J.
Author Affil Pisanu, B., Museum National d'Histoire Naturelle, Departement Ecologie et Gestion de la Biodiversite, Paris, France. Other: CSIC, Estacion Biologica de Donana, Spain; Universite de Rennes I, France
Source Polar Biology, 34(2), p.169-180. Publisher: Springer-Verlag, Berlin, Germany. ISSN: 0722-4060
Publication Date Feb. 2011
Notes In English. 84 refs. GeoRef Acc. No: 308826
Index Terms Indian Ocean Islands--Crozet Islands; biogeography; Chordata; Crozet Islands; diet; ecology; Eutheria; Indian Ocean Islands; Mammalia; Possession Island; Rodentia; subantarctic regions; Tetrapoda; Theria; Vertebrata
Abstract 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 delta 15N/delta 13C 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.
URL http://hdl.handle.net/10.1007/s00300-010-0867-z
Publication Type journal article
Record ID 91252