Figure 13.22: A Komodo dragon, the largest of the lizards, attaining a length of 10 ft. ( 28 )and others have reached sizes where they can prey on other vertebrates, such as birds and
mammals.
Many lizards are good climbers or fast sprinters. Some can run bipedally, such as the collared
lizard, and some, like the basilisk, can even run across the surface of water to escape. Many
lizards can change color in response to their environments or in times of stress (Figure
13.23). The most familiar example is the chameleon, but more subtle color changes occur in
other lizard species, such as the anole, as well.
Some lizard species, including the glass lizard and flap-footed lizards, have lost their legs
or reduced them to the point they are non-functional. However, some vestigial structures
remain. While some legless lizards, like flap-footed lizards, are similar in appearance to
snakes, they can be distinguished by such features as their external ears.
All snakes are carnivorous and can be distinguished from legless lizards by lack of eyelids,
limbs, external ears, and vestiges of forelimbs. The 2,700+ species of snakes occur in every
continent except Antarctica and range in size from the tiny, 10 cm (4 in) long thread snake
to pythons and anacondas over 5 m (17 ft) long (Figure13.24). In order to accommodate
snakes’ narrow bodies, paired organs (such as kidneys) appear one in front of the other
instead of side by side.
While venomous snakes comprise a minority of the species, some possess potent venom
capable of causing painful injury or death to humans. However, snake venom is primarily for
killing and subduing prey rather than for self-defense. All snakes are strictly carnivorous,
eating small animals including lizards, other snakes, small mammals, birds, eggs, fish, snails
or insects.