Luca Luiselli

Influences of area, isolation and habitat features on distribution of snakes in Mediterranean fragmented woodlands

The effects of isolation-related and vegetational parameters on presence and relative abundance of snakes in patchy forested fragments of Mediterranean central Italy are studied. The most abundant species was Coluber viridiflavus (accounting for 47.7% of the total snake sample observed) followed by Vipera aspis (22%), Elaphe longissima (21.5%), Natrix natrix (7.7%), and Coronella austriaca (1.1%). There was a clear trend for bigger species to be less distributed among the various forest fragments than the smaller species. Presence of Coluber viridiflavus, Coronella austriaca and Natrix natrix was not influenced by woodland area, whereas that of Vipera aspis and Elaphe longissima was positively influenced by woodland area. Woodland isolation parameters did not influence the presence of Coluber viridiflavus, Coronella austriaca and Natrix natrix, but of Vipera aspis and Elaphe longissima. Discriminant stepwise analysis suggested that specific environmental features influenced the occurrence and abundance of the various snake species, Vipera aspis being the taxon more affected by isolation-related parameters. Some conservation implications of our observations are also discussed.

Food habits of the green lizard, Lacerta bilineata, in central Italy and a reliability test of faecal pellet analysis

Abstract Food habits of the green lizard (Lacerta bilineata) were studied in some Mediterranean sites of the vicinities of Rome (Latium, central Italy), by means both of stomach dissection of individuals found already dead in the field and faeces analysis of living individuals. The taxonomic diet composition of the lizards was accurately described by both methods, thus demonstrating the reliability of faecal pellet analysis as an non‐cruel method to study lizard diets. However, by using the faeces analysis technique, it is difficult to measure the exact food intake rate (items / unit of time) as well as the size distribution of prey ingested by lizards. There was a remarkable ontogenetic change in the taxonomic diet composition of green lizards: adults essentially consumed beetles and isopods, whereas juveniles fed mainly upon orthopterans, spiders, and Rhynchota. Cannibalism and predation upon small vertebrates (lizards) were very rare events. It is suggested that (i) age‐related differences in microhabi...

Resource partitioning in a Mediterranean lizard community

Abstract Some aspects of community ecology in a lizard assemblage composed of three sympatric and diurnal species (Algyroides fitzingeri, Podarcis tiliguerta, Chalcides ocellatus) were studied in a Mediterranean habitat of central Sardinia. The three lizards were characterized by significantly different mean body size. There was no spatial overlap between the smallest species (A. fitzingeri) and the largest one (C. ocellatus), while there was a certain amount of overlap between P. tiliguerta and each of the other two lizards. The three species preyed on a wide variety of invertebrates, but mainly on insects. Food niche breadth was higher in P. tiliguerta, and this could be related to the higher microhabitat heterogeneity of this lizard in the study area. Food niche overlap was high between Chalcides ocellatus and Podarcis tiliguerta, but low between Algyroides fitzingeri and C. ocellatus. Although further data are required before any firm conclusion can be drawn, the results of this investigation seem to ...

Habitat choice by melanistic and cryptically coloured morphs of the adder, Vípera berus

Abstract Melanistic adders (Vipera berus) have been considered to be ecologically superior to cryptic ones in cold climates because of their higher thermoregulatory efficiency. However, a popular hypothesis states that black snakes should be more exposed than cryptic ones to visually oriented predation, and that the frequency of both colour morphs within a given population is maintained by the equilibrium existing between the reproductive advantage and the higher risk of predation of the melanistic morph (ESS model). Moreover, because of this higher risk of predation, it has been suggested that black adders should essentially inhabit forested zones, where they can escape from visually oriented predation. To test this hypothesis, we performed a field study on habitat choice by a polymorphic population of adders. Our data showed that habitat choice by adders strongly depended on seasonally, but not on colour pattern. Adders almost always selected open habitat in spring (during the mating period), and a vari...

The blue-spotted morph of the slow worm, Anguis fragilis: Colour polymorphism and predation risks

Abstract Blue‐spotted individuals are found in many populations of the slow worm (Anguis fragilis) throughout Europe. The frequency of occurrence of this colour morph was studied in eight populations from a mountainous territory of northeastern Italy (Tarvisio Forest, Carnic Alps, 750–1600 m a.s.l.). Blue‐spotted individuals were very rare (0.8% of the total sample; n = 744). However, the population inhabiting the town of Tarvisio presented a significantly higher proportion of blue‐spotted individuals than did the other sampled populations. All the blue‐spotted individuals were adult males of large size (average SVL = 173.5 ± 6.8 mm), with heavy body (average body mass = 41 ± 6 g), while the sole blue‐spotted animal captured in Valais was subadult. The presence of blue‐spotted animals within a population was apparently not correlated with habitat type, altitude and latitude, but was positively correlated with increase of longitude from Greenwich (Spearmans r = 0.73, n = 8, P = 0.038). A predation experim...

Is there a different preference in the choice of background colour between melanistic and cryptically coloured morphs of the adder, Vipera berus?

Abstract Most natural populations of the adder (Vipera berus), including both cryptically coloured (zig‐zag) and melanistic (black) individuals, are polymorphic in dorsal colour pattern. In this study we report experiments to test whether a difference in preference of background colour exists between these morphs. The occurrence of this difference between colour morphs was studied in (1) indoor and outdoor enclosures, (2) basking and not‐basking animals, (3) during daylight and nocturnal hours. Our data show that cryptically coloured and melanistic adders manifest a nearly identical preference in their choice of background colour, both in daylight and nocturnal hours: i.e., a clear‐cut preference for dark substrates independent of sex. Some hypotheses are put forward to explain this preference.

Ecological correlates of colour pattern polymorphism along the transition zone between two morphs of the common wall lizard, Podarcis muralis

The ecological correlates of dorsal colour pattern polymorphism were studied along the transition zone between two supposed subspecies ( = colour pattern types in this article) of the common wall lizard, Podarcis muralis, in a hilly area of Latium, Central Italy. In this area two supposed subspecies, i.e. P. m. brueggemanni and P. m. nigriventris, are known to occur. Lizards were studied along 500 m long transects within three different habitat types, i.e. wood, wall, and bushy pasture. A total of 279 adult lizards (154 males, 125 females) were examined. Three colour morphs were observed at each site, i.e. brueggemanni type (brown–green upper parts), nigriventris type (black–green upper parts), and a colour morph intermediate between the two. The distribution and abundance of brueggemanni and nigriventris colour morphs was clearly non‐random across habitat types: brueggemanni was abundant in walls and bushy pastures, and nigriventris in wood. To explain the observed pattern we tested the hypothesis of a differential predation exposure by the various colour morphs in different habitats by analysing the differences between colour morph frequencies of lizards with intact tail and with broken/regenerated tail in the various habitats of the study area. Our analysis would not support the differential predation‐risk hypothesis, because the frequency of individuals with broken tails was very similar in the three colour morphs among different habitats.