Le peuplement herpétologique d’un massif du Haut-Languedoc. II. Influence de quelques facteurs sur la répartition des reptiles

Abstract

The plant community structure and the influence of some climatic factors on the distribution and population density of the reptiles of the Caroux-Espinouze mountain range (Southern France) are discussed. Fixed transects counts were used to estimate species distribution and abundance. The activity of the Mediterranean species is influenced more by wind speed and temperature than that of more northern species, e.g. Vipera aspis. The climate of the area, which is intermediate between the Mediterranean and the Atlantic climates, exerts a strong influence on the population density of the reptile species in question. The structure of the reptile community may vary from year to year depending upon short term climatic fluctuations. The structure of the plant communities also influences the structure of the reptilian communities, and the population density of the species concerned. Heathland communities with a closed canopy growing on a deep soil harbour the denser and more diverse reptile communities of the area. This may be correlated with the availability of numerous shelters, including rodent burrows, and of many prey species ; behavioural thermoregulation may also be facilitated. Species diversity and population density decrease in more open heathland communities, meadows and forests. Three groups of species can be distinguished on the basis of their range of habitats : (1) those with a wide range : Elaphe longissima, Lacerta viridis, Malpodon monspessulanus, Natrix maura ; (2) those with a moderate range of habitats : Vipera aspis, Elaphe scalaris, Anguis fragilis, Coluber viridiflavus, Natrix natrix, Lacerta muralis ; and (3) those with a narrow range of habitats : Psammodromus algirus, Lacerta lepida and L. vivipara.