Although not the most glamorous, lava lizards are the Galapagos Islands' most abundant reptile. These are lizards with attitude! They
share with other Galapagos animals a relative lack of fear and will allow the observer to approach quite closely.
Seven species of lava lizards (all in the genus Tropidurus) are described from the islands and each of the central islands are inhabited by
a species. Lava lizards are absent from the northern outer islands, Tower, Darwin and Wolf. Such a distribution suggests a single colonization event,
perhaps on one of the central islands, and subsequent evolution and adaptive radation resulting in the present scenario. The ancestral species would
have come from South America from where some 25 species are known (although this group's taxonomy is presently in flux, see
Lizards of the World - Tropidurus).
Lava lizards grow up to a foot in length but are usually about five or six inches. They are variously and quite beautifully colored, from mottled gray, or
speckled copper to black with gold stripes. Males differ from females, being more brightly colored and much larger. The throat is black and yellow
in males but mostly red in females. Colors and size differ between the species and even within species. On one island which has only one species, you
will see grayish yellow individuals near the beach but further up among the black lava rocks, the same species of lizard is much darker. Individual
lizards will also change color according to the temperature or if they are threatened (a feature common to lizards generally).
They are voracious predators of invertebrates and instances of cannibalism are well-documented. They may have a controlling effect on insects,
preventing those such as the painted locust from over-population. The extent to which
they control introduced insects would be an interesting line of study. During dry spells, lava lizards will eat plant material.
Lava lizard males are especially territorial, staking out a prominent spot atop a boulder and bobbing their heads up and down to indicate ownership.
This so-called "push-up" behavior becomes pronounced during breeding, which peaks in the warm season. Males have larger territories which
may encompass several belonging to females.
The reproduction of these creatures is a fleeting affair, with resident males mating with females passing through their territory. Every month or so
three to six tiny eggs about the size of a pea are laid, usually deep in soil excavated by the female. After about 12 weeks the young emerge, about
two inches long. This is when they are most vulnerable to predation by birds, snakes and even the giant centipede. This may be one reason for
communal nesting in which many females share the same area for their burrows. Males take longer to reach maturity, about three years, compared with
nine months for the female. Initially cryptically colored (camouflaged) to avoid predators males look like small females but after a year or so
assume the typical male coloration.
Like all reptiles, lava lizards rely on the sun for their internal heat. Their day begins with basking a warm rock for a half hour or so. Then they are active hunting
but retreat to a shady spot during the heat of day. As temperatures fall again, they become active once more. At night they rest under leaf litter or
gravel to protect themselves from the cool of the night.