Saturday, 22 March 2014

Quest for the Wild Canary Part 4: Reptiles and Amphibians

Tenerife Lizard
Reptiles of various species are usually good at colonising islands, and the Canaries are home to a diverse range of endemic lizards. There are no native snakes, and at present no native land tortoises, although fossil; ones are known. It is probable that in the past various species of sea turtles also nested, but today they are only seen at sea. The most common of these is the Loggerhead Turtle, Caretta caretta, which also breeds in the Mediterranean. There are even a few reports of Leatherback Turtles beaching on some of the eastern islands, but no proof of nesting or nesting attempts.

Stripeless Tree Frog
Having been surrounded by salt water their entire history there of course no native amphibians on the islands. People have changed this though, with introduced populations of water frogs Rana perezi in some areas and more widespread Stripeless Tree Frogs Hyla meridionalis (the latter are common around banana plantations). Given how uncommon natural open water bodies are on the islands these amphibians are unlikely to spread away from human modified areas.

Gran Canaria skink
Chalcides skinks are a widespread group with three species known from the various islands. As they are burrowing animals the casual visitor is unlikely to see one.

Boetger's Wall Gecko
Geckos are extremely good at colonising islands and the various islands in the Canaries are home to four species of Tarentola wall geckos. There is usually only one species per island, but today they also face competition from the widespread House Gecko Hemidactylus turcicus. This last tends to stay near human habitations at present though.

El Hiero Giant Lizard
The most distinctive of the endemic lizards are the nine species of Gallotia, mostly small to medium sized lizards which in behaviour resemble the common Podarcis wall lizards that can be seen around the Mediterranean. This genus is endemic to the islands, and is most closely related to the Psammodromus lizards found in northern Africa and south west Europe. The Gallotia species can be divided into two main groups, a basal group of mostly small (except for G. stehlini on Gran Canaria) species which are mostly insectivorous, and a group on the western islands which include both small insectivorous species and very large, omnivorous or herbivorous species. The largest of the giant forms, G.goliath from Tenerife, reached as much as 1m long and is now sadly extinct. Many of the other giant lizards were believed to be extinct as well, but in recent years a few relict populations have been discovered and are the subject of intensive conservation efforts. The survivors are all much smaller than their ancestors, probably a result of heavy predation on larger individuals by the feral cats the islands small with, and also the restricted food supply in their last refuges. These are mostly off shore islands or steep cliffs in remote areas, and constitute another threat – an avalanche or severe storm could easily wipe out the remaining wild populations.
In recent years another threat has arisen on Gran Canaria, the only island where large Gallotia lizards are reasonably widespread. These are G.stehlini, and at least at present are listed as Least Concern by the IUCN. Unfortunately released pet Californian Kingsnakes Lampropeltis californiae are now breeding in the wild, and as these are reptile predators in the wild they pose a grave risk to the native lizards.

Details of species shown:
Stripeless Tree Frog Hyla meridionalis (from Wikipedia)
Boetgers Wall Gecko Tarentola boetgeri (Gran Canaria) (from Wikipedia)
Gran Canaria Skink Chalcides sexlineatus (from Wikipedia)
El Hiero Giant Lizard Gallotia simonyi (from Wikipedia)
Tenerife Lizard Gallotia galloti (own photo)

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