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M. Masseti: Homogenisation and the loss of biodiversity of mammals of the Mediterranean islands 187
also reported from Lesbos (Pieper 1981, Niethammer
1989). The Guenther’s vole, Microtus guentheri Danford
and Alston 1880, is known at present only on Lesbos
(Pieper 1981, Niethammer 1989, Krysˇ tufek 1999a), while
a subfossil form of the same species, characterised by
very large size, has been documented amongst the Holo-
cene fauna of the island of Chios (Eastern Aegean Sea)
(Besenecker et al. 1972, Kock 1974). Snow voles, Chio-
nomys nivalis Martins 1842, have been found only in
Euboea, where they have been reported from Mount Dir-
phys, at an altitude of 1700 m above sea level (Ondrias
1965, 1966). Cheylan (1988) also reported from Euboea
the occurrence of the common pine vole, Microtus sub-
terraneus de Se´ lys-Longchamos 1836, whereas Nie-
thammer and Krapp (1978) and Krysˇ tufek (1999b)
observed that this species is absent from the entire Med-
iterranean coast and islands.
Widespread in the continental areas and islands of
more northerly Europe, voles are effectively considerably
less diffuse in the Mediterranean insular ambits (cf. Cor-
bet and Harris 1991, Corbet 1978, Mitchell-Jones et al.
1999), even if, as we have seen, the biogeography of
Corsica, Sardinia and Malta was at length characterised
by the presence of several endemic representatives of
this taxonomic group. Beyond those just mentioned, very
few other Mediterranean islands are known to be pres-
ently inhabited by voles. These are essentially Krk, in the
Quarnero Gulf (Croatia), from where Tvrtkovic´ et al.
(1985) dubiously recorded the presence of the bank vole,
Myodes glareolus Schreber 1780, and the common vole,
and Elba from where the Savi’s pine vole was reported
only once by Vesmanis and Hutterer (1980) and has nev-
er since been found in any of the subsequent studies
conducted on the island (Contoli et al. 1988, Agnelli
1996, De Marinis and Masseti 1996, Nappi 2001). The
Guenther’s vole is also dispersed in Cyrenaica (north-
eastern Libya), which can be regarded as an ecological
island, being the only territory of the entire African con-
tinent where a representative of the Microtinae family
occurs (Schlitter 1989). Since being reported in the fau-
nistic associations of the island of Levanzo (Egades) in
cultural contexts attributed to the late Upper Palaeolithic
(Cassoli and Tagliacozzo 1982), the Eurasian water vole,
Arvicola amphibius (L. 1758), appears to have survived
in Sicily through the Neolithic chronologies (Grotta del
Cavallo, Castellammare del Golfo, Trapani; Contrada
Stretto di Partanna, Trapani) (Burgio et al. 2002, 2005,
Cimo` et al. 2005) up to relatively recent times (Casamen-
to and Sara` 1995). The only modern record of its pres-
ence on the large Mediterranean island registered around
the end of the 1950s by Pasa (1959) has been seriously
questioned by Casamento and Sara` (1995), who were not
able to confirm this vole as belonging to the present Sici-
lian fauna. Off the more northerly Tyrrhenian coast, some
remains of the species – recently retrieved in Bronze Age
archaeological contexts of the small islet of Vivara, in the on islands (Towns et al. 2006). Because they are omnivor-
Flegrean archipelago (Gulf of Naples) (Nappi and Caran-
nante 2003, Carannante et al. 2005) – raise further inter-
esting questions about the appearance of this vole in
these territories. The present paucity of voles in the Med-
iterranean islands may even be related to the particular
xerothermic conditions of these regions. In Israel, for
instance, evidence of the occurrence of the Eurasian
water vole was found only in barn owls’ pellets on the
banks of the lake of Hula before this was drained during
the early 1950s (Dor 1947), and it would appear to have
been extirpated as a consequence of this event (Diment-
man et al. 1992, Mendelssohn and Yom-Tov 1999)
(Figure 22).
Based on the information provided by Pasa (1959), we
could hypothesise that in Sicily too the presence of the
species was documented only for chronologies prior to
the definitive drainage of the wetlands of the surround-
ings of Agrigento. Moreover, regarding the assumption
that Eurasian water voles were part of the Holocene
fauna of Sicily, up to 1872 Doderlein (1872) claimed to
have sighted numerous populations of this rodent in the
marshes in the southern part of the island. The progres-
sive desiccation of terrain in the Holocene as opposed
to the Pleistocene might favour the survival of only those
voles of more aquatic characteristics, such as precisely
Arvicola amphibius. Instead in northern Europe, in more
favourable conditions of humidity, this vole loses its more
markedly aquatic capacities, expressing populations of a
completely terrestrial nature. Furthermore, chrono-geo-
graphical data and molecular phylogenetic studies could
sustain the possibility that the Italian water vole repre-
sents a taxon distinct from the other central and western
populations grouped within A. amphibious (cf. Masini et
al. 2007).
Invasive alien species
As observed by Cucchi et al. (2005) and Cucchi and
Vigne (2006), the success of island colonisation by small
commensal mammals depends on the magnitude of the
migrant flow and the availability of an ecological niche
for the new migrants. Since very ancient times, migrant
flow has been supported by the maritime traffic which
enabled micromammals to reach territories they would
have been unable to access independently. The availa-
bility of a favourable ecological niche depends on the
intensity of human settlement and the presence of
autochthonous rodents representing potential competi-
tors and acting as an ecological barrier. Today, invasive
rodents occur on over 80% of the world’s major islands
and continue to be introduced (Atkinson 1985, Pitman et
al. 2005).
Amongst rodents, the generalist species currently
most widespread on the Mediterranean islands are those
commensal to man: apart from the aforementioned spiny
mouse, these consist essentially of the house mouse,
and both the brown rat, Rattus norvegicus Berkenhout
1769 and the black rat or ship rat (Masseti 2002b). Rats
and house mice are most likely responsible for the
greatest number of extinctions and ecosystem changes
ous, their feeding habits affect plants, invertebrates, rep-
tiles, mammals and birds (Atkinson 1985, Cuthbert and
Hilton 2004, Towns et al. 2006, Howald et al. 2007). More
specifically, rats are efficient predators of eggs, large
insects, large reptiles, tortoises, birds and plants. They
compete for food sources with herbivores and also cause