Seabird recovery and vegetation dynamics after Norway rat eradication at Tromelin Island, western Indian Ocean

• Published in: Biological Conservation
• Main Authors: Le Corre, Matthieu, Danckwerts, D. K., Ringler, David, Bastien, Matthieu, Orlowski, S., Morey Rubio, C., Pinaud, David, Micol, Thierry
• Other Authors: Laboratoire d'Ecologie Marine (ECOMAR), Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Department of Zoology and Entomology Rhodes University, Rhodes University, Grahamstown, Terres Australes et Antarctiques Françaises (T.A.A.F.), Terres Australes et Antarctiques Françaises, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Ligue pour la Protection des Oiseaux, Bird Life International Partner in France
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: Interspecific interactions; Habitat restoration; Seabird ecology; Soil manuring; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDV.BA.ZV]Life Sciences [q-bio]/Animal biology/Vertebrate Zoology; Norway; Indian; Rattus rattus
• Online Access: https://hal.science/hal-01207081; https://hal.science/hal-01207081/document; https://hal.science/hal-01207081/file/Seabird%20recovery%20and%20vegetation%20dynamics%20after%20Norway%20rat%20eradication_hal%20%282%29.pdf; https://doi.org/10.1016/j.biocon.2014.12.015

International audience Seabirds are notoriously sensitive to introduced mammalian predators and eradication programs have benefitted seabird populations and their habitats on numerous islands throughout the world. However, less evidence is available from the tropics as to the benefits of rat eradication. Here, we report the seabird recovery and vegetation dynamics on a small coralline island of the tropical western Indian Ocean, eight years after Norway rat (Rattus norvegicus) eradication. Two species of seabirds were breeding before rat eradication (red-footed and masked boobies, Sula sula and Sula, dactylatra) and, in both species, the number of breeding pairs had an apparent increase of 22–23% per year after rat eradication. Such a highannual growth rate cannot be achieved by auto-recruitment only and our data suggest that immigration from other source populations never occurred in at least one of these species. We suggest that it is rather due to a rapid increase in breeding success, which rapidly increased the observed number of breeders since birds remained in the available-for-counting-as-breeders group for much longer. Two other species, the white tern (Gygis alba) and the brown booby (Sula leucogaster) were recorded breeding in 2014. The former species has not bred on the island since 1856 and the latter has never bred on the island. Plant cover (monospecific formation of the ruderal herb Boerhavia diffusa) dramatically increased from less than 30% of surface coverage to more than 70%. Although the initial restoration project was to eradicate all introduced mammals of the island simultaneously, house mouse (Mus musculus) eradication failed. Mouse density was high 8 years after rat eradication (32 mice/ha in dry season and 52 mice/ha in rainy season) but not higher than at a comparable tropical island of the region (Juan de Nova) where mice coexistwith introduced black rats (Rattus rattus) and feral cats (Felis catus). These results are discussed in terms of the direct positive effects of rat ...