Veronica Larosa

• Biodiversity Journal, 3 (4): 493-500

  Agatino M. Siracusa, Veronica Larosa & Ettore Petralia
  Presence of black rat Rattus rattus (Linnaeus, 1758) (Mammalia Rodentia) and possible extinction risk for micro insular populations of Podarcis sicula (Rafinesque, 1810) (Reptilia Lacertidae): the example of Lachea islet (Sicily, Italy)

  ABSTRACT
  The black rat Rattus rattus (Linnaeus, 1758) in insular environments represents a threat for many species of vertebrates, invertebrates and plants, especially in equatorial islands. In the Mediterranean Basin as regards the herpetofauna, and lizards of the genus Podarcis in particular, the information available are still few. Since 2006, a study was initiated to verify the possible impact of the black rat on the micro-insular population of Podarcis sicula (Rafinesque, 1810) living in Lachea island, a natural reserve. During 2011 were collected and analyzed 2873 excrements of rats and in no case were found remains attributable to Podarcis sicula. The density of lizards, observed with the technique of the transept, was 0.3 ind./10 m². During the period 2006-2011 were analyzed (also by molecular type investigation) a total of 4696 excrements of rat, with no confirmation of predation against Podarcis sicula. However the rat predation on insects may cause an indirect effect like competition and have negative effects on populations of invertebrates and therefore also on Podarcis sicula. Moreover the Lachea island is affected by a moderate tourism. The lizards, in those very frequented areas, show lower values of the body condition index and a decrease of cells responsible for immune response. Although is not documented any form of predation by the black rat, that species is a potential source of threat and a combined action of the factors mentioned with accidental events, makes this small micro-insular population of Podarcis sicula as vulnerable to sudden decreases in numbers.

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