Investigating native and introduced predators involvement in pathogen maintenance and spread within and among endangered seabird colonies

Abstract

**Abstract:** Accumulating evidence suggest that infectious diseases represent a significant threat to seabird populations. Characterizing the reservoir community of pathogenic infectious agents is key to identify, and potentially limit, pathogen re-emergence and spread. Due to their foraging behaviours, terrestrial predating and/or scavenging species have the potential to play critical roles in epidemiological dynamics by introducing, maintaining pathogens and/or enhancing their circulation within and among seabird colonies. On Amsterdam Island (Southern Indian Ocean), avian cholera, caused by Pasteurella multocida bacteria, has been causing recurrent die-offs of albatross and penguin nestlings since the 1980's, threatening the viability of these populations. We investigated the potential role of native brown skuas Stercorarius antarcticus and introduced rodents (Rattus norvegicus and Mus musculus) in avian cholera outbreaks by combining classical epidemiological tools with population and foraging ecology approaches. At the height of the avian cholera epizootics, both rodents and skuas carried P. multocida. Movement tracking of skuas revealed that they do not defend individual foraging territories, and that a given individual could visit several seabird colonies within a day, creating opportunities for pathogen spread at the island scale. In contrast, rodents may contribute to pathogen spread at a smaller, within-colony, scale. During winter, when most seabirds have migrated at sea, rodents still carried P. multocida bacteria, suggesting that they may play a critical role in the inter-annual maintenance of the bacteria. Based on these empirical results, we discuss the potential management strategies that could be designed to limit pathogen re-emergence and spread in seabird communities. Overall, this study highlight the benefit of broadening field investigations beyond classical epidemiological data and beyond the obviously affected species in order to better understand epidemiological processes in seabird communities and implement efficient surveillance and management measures. **Authors:** Amandine Gamble¹, Augustin Clessin², Baudouin Des Monstiers³, Lorien Boujot³, Romain Bazire², Romain Dedet⁴, Marine Bely², Erwan Lagadec³, Jean-Baptise Thiebot³, Audrey Jaeger³, Camille Lebarbenchon⁵, Pablo Tortosa⁵, Eric Thibault⁶, Christophe Barbraud⁷, Karine Delord⁷, Henri Weimerskirch⁷, Jérémy Tornos⁸, Romain Garnier⁹, Hubert Gantelet⁶, Nicolas Keck⁴, Thierry Boulinier¹⁰ ¹University of California Los Angeles, ²Centre d'Ecologie Fonctionnelle et Evolutive, ³Réserve Naturelle Nationale des Terres Australes Françaises, ⁴Laboratoire Départemental Vétérinaire de l'Hérault, ⁵Université de la Réunion, ⁶Ceva Biovac, ⁷Centre d'Etudes Biologiques de Chizé, CNRS, ⁸Centre d'Ecologie Fonctionnelle et Evolutive, Ceva Biovac, ⁹Georgetown University, ¹⁰Centre d'Ecologie Fonctionnelle et Evolutive, CNRS