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188 M. Masseti: Homogenisation and the loss of biodiversity of mammals of the Mediterranean islands

Figure 22 Present distribution of the representatives of the taxonomic group of Arvicolinae on the Mediterranean islands. The
occurrence of the Guenther’s vole, Microtus guentheri Danford and Alston 1880, in continental North Africa (Cyrenaica, Libya) and
the location of the Hula Lake (Israel) are also indicated.

agricultural damage. Moreover, rats are the vectors of (Tvrtkovic´ et al. 1985), the Tuscan archipelago (De Mari-
leptospyrosis, a disease that can be deadly to humans nis et al. 1996), the Egades (Krapp 1970), the Pelagian
and animals if not treated quickly (cf. Pascal et al. 2006). islands (Masseti and Zava 2002b), and the archipelagos
of La Galite (Vesmanis 1972) and Malta (Lanfranco 1969,
The black rat is the most successful island colonist Schembri 1993). In the Italian seas alone, out of a total
(Martin et al. 2000). Today, it is found on all continents of of 150 islands of a surface area ranging between 0.04
the earth. Although the species is believed to be native and 22,000 ha censused for rat presence/absence, the
to the Middle East, it has been introduced to all conti- black rat was recorded in 83% of islands (Paolo Sposimo
nents through human overseas travel (cf. Masseti 2002b). 2008, personal communication). Predation upon insular
It is widespread in forests and woodlands as well as vertebrates by the black rat is considered a profoundly
being able to live in and around buildings. It feeds on limiting factor for local biodiversity (cf. Orueta 2002). This
and damages almost any edible item. It is very agile and rodent is in fact regarded as probably the single most
often frequents tree tops, searching for food and nesting dangerous and detrimental alien species currently affect-
there in bunches of leaves and twigs. Ship rats are fre- ing the insular ecosystems of the whole world (cf. Lowe
quently associated with catastrophic declines in bird et al. 2000), which explains various recent eradication
populations on islands (cf. Benchley 1999, Long 2003, campaigns (Orueta 2002, Genovesi 2002, 2005). Tech-
De Marchi et al. 2006, Harris et al. 2007). Subject of an niques for eradicating rodents from islands were devel-
artificial diffusion beyond its homeland that is relatively oped over two decades ago (Howald et al. 2007). Since
recent in chronological terms and a consequence of that time there has been a significant development and
human activity (Vigne 1992, Masseti 1995b, Pascal et al. application of this conservation tool. Although worldwide
2006), the black rat is regarded as the most widespread 332 successful rodent eradications have been undertak-
invasive taxon of the alien species that continue to thrive en, not many have been carried out so far in the Medi-
on Mediterranean islands. Amongst the 292 Mediterra- terranean basin, one of the first being performed
nean islands examined in a recent review by Ruffino et successfully in the Spanish archipelago of Chafarinas, off
al. (2009), comprising records of rat presence or the Mediterranean coast of Morocco (Orueta 2002).
absence, 201 (69%) were rat-infested, with the smallest
rat-infested islet being 0.021 ha. The rodents were found The invasion of ecosystems by exotic taxa is currently
on 36% of islands of -0.5 ha and on 99% of islands of viewed as one of the most important causes of the loss
)30 ha. Rattus rattus is the most common non-volant of biodiversity (Elton 1958, Hengeveld 1989, Shine et al.
mammalian species in the Central Mediterranean archi- 2000, Pascal et al. 2006). Invasive alien species are reco-
pelagos, including the islands of Hye` res (Granjon and gnised as one of the major causes of habitat destruction
Cheylan 1990, Libois et al. 1996), the Quarnero islands on a global scale, and islands are particularly vulnerable