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1642 L. Ruffino et al.

coexistence is likely to provide important clues to
(1985) (unpublished (2005), 2008) conservation and restoration priorities on other rat-
Vidal Pascal (2006, (1997) invaded islands worldwide. Here we hypothesize that
the long-term persistence of these seabirds at the scale
(1985), (1995) and al. et al. et of the Western Mediterranean Basin may have been
facilitated by the various biogeographical contexts of
References Cheylan CEEP-Marseille report) Thibault Lorvelec Pascal Thibault Mediterranean islands, providing intra-island refuge
areas where interactions with introduced rats may be
limited. Rat densities on islands and their fluctuations
over time are known to be major factors in seabird
vulnerability within breeding sites (e.g., Igual et al.
populations from increased chicks/ after 75% nearly in failure increased after Gargalu: Giraglia: 2006), with seabird productivity increasing when rat
densities are low (Quillfeldt et al. 2008). This
intriguing coexistence, along with evidence of rat
seabird fluctuated year success fledged and 65% for breeding years success 83% to on success on rats), rats) (without impact on Mediterranean seabirds, also raises new
questions on the mechanisms and the intensity by
on impact to 25% to control responsible of 44% eradication (with which invasive rats really affect seabirds, and on their
ability to drive them to extinction. More work is also
Effects Rat year Breeding from adult rat Rats 85% certain Breeding from Breeding 3% 73% needed to clarify the complex relationships linking
factors likely to influence rat population densities (i.e.,
diversity of available resources, presence of other
alien predators or competitors on islands), foraging
affected chicks and mainly strategy of rats and rat impact on seabird populations.
As claimed by Towns et al. (2006), we suggest that the
Stage Eggs Chicks ? ? role of rats in seabird population decline should be
carefully evaluated relative to that of other factors and
caution should be used in attributing any seabird
Species Y C C C C breeding failures, and local or global extinctions to
rats. The better we understand both patterns and
mechanisms causing decline, the better we can focus
our efforts on the most effective measures to mitigate
threats.
Giraglia Acknowledgments We would like to thank all the people

and Porquerolles and and who provided data, contacts, unpublished reports, and other
information: H. Azafzaf, J. Borg, G. Brundu, F. Corbi, C. Cure ´,
J. Fric, J. M. Igual, M. Louzao, A. Martinez Abrain, B. Massa,
Island Port-Cros Pomegues ` Ratonneau Lavezzu Lavezzu Gargalu F. Me ´dail, R. Moulia, S. Pasta, J. D. Vigne. We also thank D.
Drake and T. Hunt for inviting us to write this paper, M.
Sweetko for improving the English, Y. Delettre (CNRS, UMR
6553 Ecobio, Rennes), and two anonymous referees for helpful
comments on earlier drafts of the manuscript. Funds were
Marseilles Corsica Corsica provided by a PhD fellowship granted by the ‘‘Ecole Doctorale
des Sciences de l’Environnement’’ to L. R. and by a post-
doctoral fellowship from the ANR (‘‘ALIENS’’ project) to K. B.

continued Area ` Hyeres Frioul, Lavezzi, Northern Appendix 1

5
Table Country France See Table 6.

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