There are seven different lizard species inhabiting the Canarias; all seven are endemic to the islands and fall within the Gallotia genus, which is in turn also indigenous to the archipelago. Four of the above species are regarded as giant lizards, even though none of them measure over 80 cm in length: Gallotia stehlini from Gran Canaria, Gallotia simonyi, found on El Hierro, Gallotia bravoana of La Gomera and Gallotia intermediafrom Tenerife. The last three were thought to be extinct up until recent years, but small groups of specimens have been discovered in extremely remote and rugged areas on said islands. Remains of yet another two species considered to have become extinct have been dug out of paleontological and archeologic sites in Tenerife. These are Gallotia goliath and Gallotia maxima and they reached larger sizes than those seen in giant lizards currently living on the island -certain researchers believe however that these would be but very large specimens of the abovementioned species-.
In order to track the origin of these species down, we need to look into a series of isolated colonization events taking place from the African continent and towards the easternmost islands -the eldest in the archipelago- millions of years ago. These initial settlers would then have evolved within the insular environment and have favoured dispersal and colonization events in between the islands. The small founding populations would have contributed to an island-based speciation process. It is believed that the first African settlers were small lizards that evolved into giant specimens within the islands, where this sort of phenomena are relatively commonplace. Similarly to other species of lizards, these are omnivore animals feeding on sprouts, fruits, insects and small vertebrates. In order to reproduce, they will bury their egg lay in the ground. Their fertility rates are on the lower end, comparatively.
Circumstances changed for these lizards following the arrival of the first human settlers to the Canarian archipelago. This was the beginning of the decline in their populations. The process was sped up further with the European colonization and the introduction of domesticated predatory species, namely the domestic cat. Human populations having taken over large areas of the islands and domesticated predatory species having become feral, lizards have been put in an extremely vulnerable situation. They have currently been declared as endangered species by several national and international organizations and recovery plans for two of the species -the ones found in La Gomera and El Hierro- are being carried out. These consist of captive breeding and the subsequent release of specimens into areas that supposedly show the necessary conditions for them to thrive in. A very much needed recovery plan for Gallotia intermedia, the species inhabiting Tenerife, is yet to be designed. Only two population hubs are known on the island -one in Los Gigantes and another one in Montaña de Guaza-, gathering an estimated total of less than a thousand specimens.
These recovery initiatives for the giant lizards are highly important, but for restocking operations to be successful it is necessary to conduct previous checks on feral predators -especially cats-.