Diet of the asp viper Vipera aspis in woodland habitats of the Po plain (NW Italy) Luca Canova, Augusto Gentilli Dipartimento di Biologia Animale, Università di Pavia, Piazza Botta 9, I-27100 Pavia. Corresponding author. E-mail: canova@unipv.it Submitted on 2007, 5th November; revised on 2008, 28th January; accepted on 2008, 31st January. Abstract. The diet of Asp viper Vipera aspis was studied in forested habitat of North- ern Italy The species feeds on a low number of preys, possibly reflecting the reduction of small mammal richness in woodland habitats. Keywords. Vipera aspis, diet, prey list, northern Italy. The diet of the Asp viper Vipera aspis has been extensively studied all over its distri- bution range (Duguy, 1972; Monney, 1990, 1993, 1995). In Italy several studies focused on feeding ecology of populations inhabiting mountain and Mediterranean habitat (Cap- ula and Luiselli, 1990; Luiselli and Agrimi, 1991; Capizzi and Luiselli, 1996; Saviozzi and Zuffi, 1997) whereas data from temperate plain areas are scanty or anedoctal (Morisi and Molinaro, 1980; Bruno, 1985). This paucity of information is ultimately due to the 1) strong fragmentation of woodland habitat, 2) a very low population density and 3) a scarce success in ingesta collection (usually less than 30% of captured individuals regur- gitate or defecate (Gentilli, unpubl. and present study). Aim of this note is thereby to improve current knowledge of diet and feeding strategies of Asp viper in residual plain populations, as well as to compare diet spectrum and prey availability. Our study was carried out from April to September 2006 in two residual woodland are- as of Po plain (North-Western Italy). The first area was the Bosco Fontana Nature Reserve (45° 12’ 11’’N; 10° 44’ 41’’E), an ancient and mature woodland of 230 ha (hereafter BF). The protected area is uniformly covered by Quercus robur and Carpinus betulus and a wide prai- rie is located in the central part of the woodland. The second study area was the Baraggia di Piano Rosa (45° 38’ 47’’N; 8° 28’ 23’’E), a wide protected area characterized by woodlot, hedgerows and cultivated field growing on a acid and dilavated soils (hereafter B). Arboreal vegetation is dominated by Robinia pseudoacacia, Betula pendula and Quercus robur; grassy vegetation is mainly constituted by Calluna vulgaris and Molinia arundinacea. Acta Herpetologica 3(2): 175-178, 2008 ISSN 1827-9643 (online) © 2008 Firenze University Press 176 L. Canova and A. Gentilli We captured 82 Asp viper and 24 meal samples were collected by 24 individuals (13 male, 11 female). Vipers were captured by hand along the ecotone woodland-prairie; after capture, vipers were measured, sexed and stored inside cotton bag. Prey samples were obtained by forced regurgitation (ingesta) or collected after few hours of captivity (ingesta and faeces). All samples were conserved in ethanole until examination. Preys were determined by microscopical analyses of ingesta and faeces contents. Methods proposed by Debrot et al. (1982), Demarinis and Agnelli (1993) were adopted for this study; a references collection of mammals hairs was prepared and Teerink (1991) was adopted as the identification guide. Food availability was estimated on two soil level; firstly we checked for preys avail- ability above ground by disposal of 52 live traps on a standard transect 450 m long (BF) and 36 live traps on a transect 280 m long (B). Traps were baited with sunflower seeds and checked at sunset and dawn; trapped individuals were sexed, weighted, marked by toe-clipping and released. We tried to estimate prey availability underground by disposing traps under litter, but this method provided a very poor trap success; data from Canova (1992) and Nadali (2001), collected in the same habitat or similar wooded habitat, were then adopted to compare diet with underground food availability. On 24 samples only three mammals and one reptilian species were indeed recognized. Diet from the two study areas are significantly different (χ2 Fisher = 10.4, df = 3, P = 0.004), with Microtus savii being the principal prey in Bosco Fontana and Crocidura suaveolens in the Baraggia area; Rattus sp. and Anguis fragilis were occasional preys in our samples (Table 1). Diet among sexes are not significantly different (χ2 Fisher = 4.5, df = 3, P = 0.163) while diet item frequency is significantly different from availability (χ2 = 29.7, d.f. = 5, P < 0.001) and availability differed among sites (χ2 Fisher = 8.7, df = 3, P < 0.01). Comparison between frequency of mammal preys and available ones showed that Apodems agrarius and Apode- mus sylvaticus are not represented in Asp viper diet; only C. suaveolens is preyed in propor- tion to its availability while M. savii proportion in diet largely overrun its availability (Fig. 1). Results suggested a diet pattern remarkably restricted, confirming the data report- ed by Capizzi and Luiselli (1996) woodland habitats of central Italy; on the other hand these data contrast with Capula and Luiselli 1990 (14 preyed species), Luiselli and Agrimi (1991) (20 preyed species) and Saviozzi and Zuffi (1997) (10 preyed species) where diet was considerably wider. The observed differences can reflect the reduction in small mammal richness in mature woodland habitat, as described by Gurnell (1985), as well as the effect of a higher Table 1. Diet of asp viper in the two study areas. Bosco Fontana Baraggia Total n % n % n Microtus savii 12 75 1 12.5 13 Crocidura suaveolens 3 18.75 6 75 9 Anguis fragilis 0 0 1 12.5 1 Rattus sp. 1 6.25 0 0 1 177Diet of Vipera aspis habitat heterogeneity in the other study areas. Out of general conclusion two additional informations appeared to be of some interest from our study: 1) Asp viper diet do not include both the diurnal A. agrarius than the nocturnal A. sylvaticus, two rodents very abundant in our study areas; 2) Asp viper feeds on C. suaveolens and largely preferred M. savii, two smaller and less abundant species in forest habitat (Canova and Fasola, 1991; Canova, 1992). More detailed study are clearly needed in order to separate effect of habitat on prey spec- trum width and to investigate possible feeding adaptation in local, fragmented populations. ACKNOWLEDGEMENTS Thanks are due to Lara Rondi for her help in sample analyses and to Dr. Franco Mason and Carlo Bider, directors of Bosco Fontana and Baraggia di Piano Rosa Nature reserve respectively for permission and facilities. This study was carried out with personal fund. REFERENCES Bruno, S. (1985): Le vipere d’Italia e d’Europa, Edagricole, Bologna. Canova, L., Fasola, M. (1991): Communities of small mammals in six biotopes of North- ern Italy. Acta Ther. 36: 73-86. Canova, L. (1992): Distribution and habitat preference of small mammals in a biotope of the North Italian plain. Boll. Zool. 59: 417-421. Fig. 1. Frequency of mammal preys in diet compared with availability. Legend: °° data from present study, ° Canova (1992). Differences were tested on original frequency by chi-square test and Bonferroni confi- dence intervals: ns=not significant, * P < 0.01, ** P < 0.001. 178 L. Canova and A. Gentilli Capula, M., Luiselli, L. 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