Hystrix, (n.s.) 11 (2) (2000): 65-74 NATIVE AND ALIEN SQUIRRELS IN ITALY SANDRO BERTOLINO", ITALO CURRADO", PETER J. MAZZOGLIO" AND GIOVANNIAMORI" * Di. Va2R.A. Entomologia e Zoologia, Universita di Torino, via L. da Vinci 44, 10095 Grugliasco (TO), Italy. O CNR, Centro Genetica Evoluzionistica, via Lancisi 29, 00161 Roma, Italy. ABSTRACT - In Italy there are four species of squirrels: the native red squirrel and other three species recently introduced. The red squirrel is present in the Italian peninsula with three subspecies, and is missing only in Salento, and Italian islands. This species is common on Alps and Apennines, while in the plains it is declining because of the habitat loss. Competition with the grey squirrel and habitat fragmentation are considered the major threats to the survival of the red squirrel. The grey squirrel is present in Piedmont and Liguria. A study on the Piedmontese colony showed that the red squirrel is disappearing from the area colonised by the grey squirrel and the damage due to bark-stripping and feeding is considerable. Free-ranging populations of the Siberian chipmunk live in Belluno, Verona, and Rome, but records of single animals were reported for other areas. The Finlayson's squirrel is pre- sent with a small nucleus in an urban area of Piedmont. Here, the impact of this species on the veg- etation appears dramatic. The eradication of the grey squirrel is a priority for the conservation of the red squirrel, but control plans for the other introduced species are also needed. Key words: Red squirrel (Sciurus vulgaris), Grey squirrel (Sciurus carolinensis), Siberian chipmunk (Tamias sibiricus), Finlayson's squirrel (Callosciurus finluysoni), alien species, Italy. INTRODUCTION but other species have been introduced late- ly. These are: the grey squirrel (Sciurus car- The introduction of alien species is one of the olinensis) that was introduced into Piedmont greatest threats to native biodiversity, only the in 1948 and into Liguria in 1966; the Siber- destruction of habitat is worse. A UN report ian chipmunk (Tamias sibiricus) released in shows that 20% of the endangered vertebrate different sites of North and Central Italy; the species are so because of introduced species Finlayson's squirrel (Callosciurus fin- (Baskin, 1996). Furthermore, a lot of aliens laysoni) introduced into Acqui Terme (AL) may interact negatively with human activi- 16-18 years ago. The presence of the grey ties, thus causing a remarkable economic loss squirrel in Italy poses a serious conservation (Lever, 1994). The Convention on Biological problem: in fact this species competes with Diversity, adopted in 1992 by the summit in the native red squirrel and causes its disap- Rio de Janeiro, and signed also by Italy, rec- pearance. The first introduction into Europe ognized these dangers and obliged all sub- of the grey squirrel occurred in Great Britain scribing nations to prevent the introduction of in the late 19th century (Laidler, 1980; new species and to control or eradicate those Lloyd, 1983). In less than a century the alien already introduced, which proved to cause a squirrel has replaced the native one over threat to the ecosystems. most of the country (Reynolds, 1985; Ush- The red squirrel (Sciurus vulgaris) is the on- er et al., 1992; Gurnell and Pepper, 1993); ly squirrel species naturally present in Italy, the same is happening in Italy (Wauters et 66 S. Bertolino et al. Table 1 - Presence of the red squirrel in different regions of Italy, differentiated in: widespread (+); localized (+I-); rare or absent (-). Data are taken from literature (Piemonte, Valle d’Aosta: S.TE.P., 1994; Lombardia: Prigioni et al., in press; Venezia: Bon et al., 1995; Friuli: Lapini et al., 1996; Gros- seto: Sforzi and Ragni, 1997; Forli: Gellini et al., 1992; Marche: Pandolfi, 1992). Area Alps Apennines Hills Plains Valle d’Aosta +/- Piemonte + +I- Lombardia +/ - +/- Venezia +I- Friuli + Grosseto + + Forli +/- Marche + ? al., 1997b). Keeping in mind this situation em Italy, there is the subspecies S. v. merid- there is a growing concern about the possi- ionalis Lucifero, 1907, having the upper ble spread of the grey squirrel throughout parts of the body black and the lower parts the European continent. white. According to Cavazza (1913, in The aim of this paper is: (i) to point out the Cagnolaro, 1981) the body size increases status of the red squirrel and of the other in- gradually from the Alps to Calabria. troduced squirrels; (ii) to list the threats for The red squirrel was hunted until 1977 and the ecosystems where these species have was considered a pest to forests in the past been introduced; (iii) to supply information (Cagnolaro, 1981); nowadays this species is for the management of these species. protected by the Italian law (no. 157/92). Until now an organic research on the status RED SQUIRREL of the red squirrel in Italy is not available, (Sciurus vulgaris Linnaeus, 1758) but some information can be collected from mammal atlases published locally (Table 1). The red squirrel has a Palaearctic distribu- In northern Italy this species is common on tion, from the Iberic peninsula to Japan. Up Alps and pre-Alps, especially where there to date about 40 subspecies have been de- are mature and well grown forests, and it is scribed, but most of them are dubious. In present on most of the hills (S.TE.P., 1994; Italy three subspecies are present (Toschi, Bon et al., 1995; Lapini et al., 1996; Prigioni 1965), and the red squirrel is missing only in et al., in press). The situation in the plains is Salento (southern Apulia) and on the islands. different; here this species is endangered and On the Alps, and more generally north of the declining because of a high habitat fragmen- Apennines, one finds the subspecies S. vul- tation preventing the possibility of recoloni- garis fuscoater Altum, 1876, which is also sation when local extintion occurs. In Vene- widespread in Central Europe. The pelage tia and Friuli, the red squirrel is almost ab- colour goes from light red to dark brown, al- sent in the plains (Bon et al., 1995; Lapini et most black. In central Italy, north of Abruz- al., 1996), while in Piedmont and Lombardy zo, there is S. v. italicus Bonaparte, 1838, al- it still occupies some large lowland woods, ways having a light and a dark phase, but but local extinctions are common (Celada er less intensively pigmented. Finally, in south- al., 1994). The information on central and Squirrels in Italy 67 Table 2 - Tactics for conserving the red squirrel in Europe. Management interventions useful to assure the survival of the red squirrel in Europe. a) Eradication of the grey squirrel from Italy. Management interventions useful to favour colonisation by the red squirrel in areas presently not oc- cupied or dwelled in a non stable manner. a) Modification of the present forms of forest management so to obtain an increase of the wilderness of woods. b) In the plains, creation of ecological corridors to link isolated areas large enough (20- 40 ha) to host a source population. c) Application of re-iqtroduction or re-stocking programmes to favour the recoloniza- tion of suitable areas. southern Italy is scanty. Gellini et al. (1992) rel (Celada et al., 1994; van Apeldoorn et consider this species common in almost all al., 1994, Verboom and van Apeldoorn, woods of the province of Forli (Romagna), 1990; Asferg et al., 1997). Wood size, pres- Sforzi and Ragni (1997) point out a positive ence of conifers, and nearby forests were trend and the colonization of new areas in positively correlated with the presence of the province of Grosseto (Tuscany), while the red squirrel. The distance from woods Pandolfi (1992) retains that the red squirrel bigger than 20-30 ha (where a source popu- is not present in all feasible environments of lation may be maintained) was negatively Marche. In any case, this species is absent correlated with the presence of this species: from some areas of Latium where there are an increasing distance decreased the chance apparently good ecologic conditions (e.g. Ci- to find a squirrel. In the only study made in mini Mounts in the province of Viterbo; Lep- Italy, Celada et al. (1994) pointed out the ini Mounts in the provinces of Rome, Latina presence of the red squirrel only in 28.3% and Frosinone; parts of the coast). The red of the 46 wood areas investigated in the Po squirrel can colonise urban areas, also of big Plain, These were near the rivers Ticino and cities, such as Rome (Cignini et al., 1997), Po, where there are still woods of a certain Bologna, Forli (Scaravelli and Di Girolamo, size. Normally red squirrels do not disperse 1998), Gorizia, Trieste and Udine (Lapini et over open habitats, thus a landscape man- al., 1996), when they host forest remnants. agement must lead to the reduction of The red squirrel is considered an endan- woodland isolation. The connection between gered species in Europe (Amori and Zima, woodland fragments containing a “source” 1994; Mitchell-Jones et al., 1999) and in population (20-40 ha in size), could be in- Italy (Amori et al., 1993). The competition creased by planting hedgerows, treerows with the grey squirrel and habitat fragmen- and small woodland patches (Wauters et al., tation are considered the major threats to the 1994; Wauters, 1997). Other management survival of this species. At a regional scale, interventions useful to safeguard this species animal population dynamics are strongly af- (Table 2) may be the increase of tree species fected by woodland isolation (Andrtn, quality and reintroduction programmes in 1994). Research carried out in areas with a areas considered suitable for the red squir- different degree of habitat fragmentation en- rel (Fornasari et al., 1997; Wauters et al., abled to point out the factors which influ- 1997a).