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1632 L. Ruffino et al.

Introduction likely to be potential seabird predators (Vigne 1992;
Marra 2005; Gippoliti and Amori 2006). With more
For thousands of years, island colonization by humans than 5,000 islands and islets, the Mediterranean Basin
and intense exploitation of native biotas have trig- comprises one of the largest groups of islands in the
gered catastrophic species extinctions on islands world, with exceptional biodiversity (Delanoe ¨ et al.
worldwide (Steadman 1995; Alcover et al. 1998; 1996;Me ´dail and Que ´zel 1997; Myers et al. 2000).
Roberts et al. 2001; Steadman and Martin 2003; This island system has been early and widely
Burney and Flannery 2005). As humans keep moving colonized by ship rats (Rattus rattus) since their
further and faster, they have scattered a large number spread from the Indian Peninsula (Audouin-Rouzeau
of species beyond their natural ranges and have been and Vigne 1994; Masseti 1995; Vigne and Valladas
responsible for an unprecedented ecological turnover 1996). The oldest reliable ship rat remains recorded
on islands (Vitousek et al. 1997; Chapin et al. 2000; in the north-western Mediterranean islands date back
Rosenzweig 2001). Rats (Rattus spp.) have been to Roman times (Corsica: 393–151 B.C., Vigne and
successfully introduced on more than 80% of the Valladas 1996; Menorca: 200–100 B.C., Audouin-
world’s major islands and are known to negatively Rouzeau and Vigne 1994), although older records are
affect island biota, especially birds (Atkinson 1985; possible (Audouin-Rouzeau and Vigne 1994). How-
Courchamp et al. 2003; Towns et al. 2006; Jones et al. ever, despite the long-standing and widespread rat
2008). Evidence of rapid bird extinctions soon after introduction and human presence on Mediterranean
rat arrival has been documented on several islands islands, no seabird species extinction has been
(e.g., Big South Cape Island in New Zealand, Midway reported in the Mediterranean Basin since rat intro-
Island in Hawaii, and Lord Howe Island, east of the duction (Alcover et al. 1992; Milberg and Tiberg
Australian mainland; Atkinson 1985; Towns et al. 1993; Vigne et al. 1997; Zotier et al. 1999), although
2006). Seabirds in particular are extremely sensitive local extirpations have occurred on some islands
to rat impact as they have generally evolved in the (Martin et al. 2000; Bourgeois and Vidal 2008). The
absence of mammalian predators and thus have not globally extinct Puffinus nestori, formerly restricted
developed any defense mechanisms (Burger and to the Balearic Archipelago, vanished during the late
Gochfeld 1994; Blackburn et al. 2004). Consequently, Pliocene before humans introduced rats on islands.
numerous cases of breeding failures, sharp decreases Among the nine seabird species currently breeding in
in breeding populations and local extirpations of the Mediterranean islands, the four endemic Procel-
seabird colonies have coincided with rat introduction lariiformes have been present since the Pleistocene
on islands (Atkinson 1985; Towns et al. 2006). Most (Alcover et al. 1992; Zotier et al. 1999). The survival
seabird species worldwide are negatively affected by of these endemic long-lived seabirds on Mediterra-
the impact of rats, especially the smallest species and nean islands, despite thousands of years of ship rat
those nesting in burrows or cavities (Imber 1976; presence, constitutes an amazing conservation para-
Atkinson 1985; Martin et al. 2000; Jones et al. 2008). dox, since this group of birds is known to be
Therefore, today, rats are identified as a leading cause negatively affected by the introduction of alien
of extinction risk in 68% of the world’s Procellarii- predators worldwide (Atkinson 1985; Birdlife Inter-
form seabirds (e.g., petrels and shearwaters, except national 2000; Jones et al. 2008).
albatrosses; Birdlife International 2000). The Mediterranean Basin may thus constitute a key
Except bats, two endemic shrews and an endemic site for studying the long-term interactions between
mouse, all terrestrial mammals currently present on introduced rats and seabirds on islands. This paper
Mediterranean islands have been introduced by man focuses on three main aims: (1) to identify factors
and the native mammal fauna found on islands during likely to explain ship rat presence on Western Medi-
the Pleistocene has been extinct since the Early terranean islands; (2) to account for how ship rat
Holocene (large mammals), or slightly later (small presence and island characteristics may have driven the
mammals) (Vigne 1992; Pascal et al. 2006). The presence and abundance of the four Mediterranean
Pleistocene mammal fauna was poor and disharmon- Procellariiformes at the scale of the Western Mediter-
ic. Most species were shrews and vegetarian rodents, ranean Basin, and (3) to review documented data of
and very few if any of these native species were rat impact on Mediterranean seabird communities.

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