Hierro Giant Lizard

Description and biology

The Hierro (pronounced YER–o) giant lizard is large compared to other lizards in its family (called lacertids). This lizard can have a body length up to 7.5 inches (19 centimeters) and a total length (including its tail) over 20 inches (51 centimeters). Most other lacertids are about one–third this size.

The body of the Hierro giant lizard is greenish–brown in color with a few large, pale yellow–tinged spots on the sides. The lizard’s head is yellowish–brown on top with irregular black marks. Around and under its jaw are large scales dotted by large pale spots surrounded by black.

Hierro giant lizards eat mainly plants, but will feed on insects such as bumblebees, grasshoppers, and ants. Once morning sunlight strikes the cliff on which they live, the lizards emerge from hiding in rock crevices. They are active all day, except for a short period around midday.

Biologists (people who study living organisms) do not have much information regarding the Hierro giant lizard’s reproductive habits.

They believe that a female, after having mated, lays a clutch (eggs produced at one time) of up to eight eggs in September in a small pocket in the sand. Some biologists think that females may lay their eggs as early as April and may breed only every other year.

Habitat and current distribution

The entire Hierro giant lizard population—totaling about 100 lizards—lives in a small area halfway up a steep cliff face on Hierro, the westernmost island in the Canary Islands (a province of Spain, this island group lies off the northwest coast of Africa, along the border between Western Sahara and Morocco).

The cliff the lizards inhabit is known on the island as Fuga de Gorreta. Hierro is volcanic in origin and very rocky, and this cliff has many boulders and crevices that provide the Hierro giant lizards with shelter. The lizards are found in an area between 1,150 and 1,640 feet (350 and 500 meters) in altitude.

History and conservation measures

Scientists first began collecting specimens of the Hierro giant lizard in the late nineteenth century. At the time, the lizard was found over most of Hierro. By the late 1930s, however, the lizard had disappeared from many areas largely due to over–collection or capture.

Since then, human development of the island and introduced predators (mainly cats and dogs) have reduced the Hierro giant lizard population to a single group on Fuga de Gorreta.

ICONA, a Spanish conservation agency, has designed a recovery plan for the Hierro giant lizard that includes protecting its remaining habitat and establishing a captive–breeding program. Although the plan has recently been set in motion, it is still too early to gauge the results.