Xenopus laevis (Daudin, 1802), a new exotic amphibian in Portugal

The African clawed frog Xenopus laevis has been introduced at several locations, including Mediterranean climate-type regions. In 2006, several individuals of this species were found inhabiting a stream at Oeiras, about 20 km W of Lisbon, Portugal. Although the place and time of introduction are not clearly identified, there are reasons to believe that this population may be the result of an almost 30-year-old introduction proceeding from research laboratories located nearby. Field surveys were conducted in 2007 and 2008 on the distribution and abundance of this species in the region. The species was found in two streams, about 5 km from each other. While being locally abundant, the adults of X. laevis are smaller than those from South Africa and California. In spite of an abundant production of eggs and tadpoles at one of the streams, no tadpoles were found in advanced developmental stages. Until now, most individuals were found in heavily urbanized areas that should constrain their ability to cross overland to other water bodies. An eradication program may be feasible, but the presence of adults on two streams indicates that the species may be expanding, in spite of the urban landscape.