Three species of reptiles, all geckos, have been introduced to the islands. In 1997-1998, a wet El Niño year, amphibians were introduced, with the arrival of the tree frog Scinax quinquefasciata.
The three species of gecko that have been introduced to Galapagos are Phyllodactylus tuberculosus (Leaf-toed gecko), Phyllodactylus reissi, and Lepidodactylus lugubris (Mourning Gecko). Six endemic gecko species are found in Galapagos. Studies indicate that the introduced geckos do not represent a serious threat to the endemic species, except for Phyllodactylus reissi, which might be displacing the endemic Phyllodactylus galapagoensis. P. reissi has a larger body size and lays more eggs. Both the endemic P. galapagoensis and the introduced P. reissi feed on moths.
The introduced tree frog Scinax quinquefasciatus appeared in Galapagos in the late 1990s. Populations have increased, although drought conditions have restricted the frogs to ponds adjacent to and in Puerto Villamil on Isabela Island. Monitoring of the frogs is important to detect their dispersal to other areas.
Methods for control of tree frogs under investigation by CDF scientists include increasing salinity of the coastal lagoons. Research results indicate that the frogs cannot tolerate salinity of more than 14% sea water. Before the method can be applied, however, it is necessary to evaluate the effects of increasing the salinity on non-target species such as fish and invertebrates that share these lagoons. Many of these species are endemic to Galapagos.
Investigation into other methods of control will also be necessary, to provide solutions for use where salinity cannot be increased.
