El Hierro giant lizard

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The El Hierro giant lizard (Gallotia simonyi machadoi) is the only living subspecies of Simony’s giant lizard. It is native to El Hierro, the western Canary Islands, and is a symbol of the island.

Size and appearance: adult males are about 120–200 mm long (not counting the tail), females about 110–160 mm. Captive lizards from Tibataje can grow larger. The tail is long, about 1.4 to 1.7 times the body length. Fossil remains show lizards were much bigger before humans arrived.

Where it lives: once widespread on El Hierro, today it survives in a small area on the Tibataje cliff (about four hectares) and on Roque Chico de Salmor islet. The Tibataje population is around 250 animals, and the Salmor population is about 120.

Diet: these lizards eat mainly plants but also insects, small animals, and even dead prey found near seabirds.

Breeding: eggs are laid mainly from June to August (sometimes a second clutch). A clutch has about 5–13 eggs. Incubation is around 61 days at roughly 28–29°C. Newborns weigh about 3–6 g and are 44–58 mm long, plus a tail of 87–133 mm. Females mature after at least four years.

Predators and threats: natural predators include birds of prey and, in the wild, feral cats and rats. Dogs once killed adults. The main defense is to run away; juveniles are especially at risk. Parasites and diseases have been recorded in the species.

Behavior and habitat: the lizards are diurnal and active most of the year, preferring a home range of about 200–300 m2. They tolerate other animals nearby and are not very territorial.

Evolution and history: genetic studies show the two subspecies diverged recently after rising sea levels in the late Pleistocene. Humans hunted lizards and cleared forests, which contributed to their decline. The species was thought extinct by the mid-20th century until rediscovered in 1975 and described as a distinct subspecies in 1989.

Conservation: the lizard was protected in 1975. A captive-breeding program began in 1986, and a LIFE program started in 1995. Several releases have been made to restore populations, and ongoing efforts aim to reduce feral cats and rats. The El Hierro giant lizard is listed as Critically Endangered by the IUCN, protected under Europe’s Habitats Directive, and listed on CITES Appendix I.