Iguanas and Other LizardsThe Green Iguana (Iguana iguana; plate 16- 74) is a
ubiquitous inhabitant of Neotropical humid forests.
These lizards are among the largest of the Neotropical
lizards. They are green when small but become grayish
brown as they grow larger and mature (plate 16- 75).
A mature iguana can exceed 1.8 m (6 ft) in length, but
much of it is tail, which tapers into a slender tip. The
face, with large mouth and wide, staring eyes, atop
the primordial reptilian body presents a dinosaur-
like countenance. (Indeed, iguanas have played the
role of dinosaurs in several very old B movies.) Two
short spines adorn the nose above the nostrils, and a
loose membrane of skin called a dewlap hangs below
the throat (plate 16- 76). The head is flat and covered
by heavy tubercle- like scaling, and the neck and back
are lined with short, flexible spines. The legs sprawl
alligator- like to the sides, and the feet have long toes
with sharp claws.
Iguanas do not often hurry, but they are capable
of moving quickly if necessary. They spend most
of their time in trees, usually along a stream or
river, into which they jump should danger threaten.
Excellent swimmers, they can remain underwater for
considerable time. When small they concentrate on
insect food but when full- size feed more heavily on
fruits and leaves. Should you encounter an iguana,
even a large one, you have nothing to fear. They
usually do not bite unless thoroughly harassed, they
are not particularly effective scratchers, and they are
nonvenomous. The most aggressive iguana I ever
encountered was directing its hostility at a rat. Both
the mammal and the reptile were contesting access
to garbage dumped alongside the Amazon River in
Iquitos, Peru. The iguana lost.
Adult iguanas feed heavily on fruits and leaves
and thus, because they are near the base of the food
chain, are apt to be abundant in rain forests. They are
a potentially important protein source for humans.
Iguanas are members of the large family Iguanidae,
which includes the many anole lizards, basilisk
lizards, and ctenosaurs. Anoles (genera Anolis and
Norops; plates 16- 77– 78) are generally abundant
lizards. Some are bright green, some are brown, and
some are mixtures of both. Some can change color,
rather like chameleons, to which they are not closely
related. During the heat of the day the sounds of these
and other small lizards scurrying over dry leaves
precedes you as you walk along. Anoles have sharplyPlate 16- 74. Green Iguanas, which are not always green, look
prehistoric. Photo by Gina Nichol.
Plate 16- 75. This young Green Iguana is indeed green. Its color
will change as it ages. Photo by Dennis Paulson.
Plate 16- 76. The dewlap is readily visible on this Green Iguana.
Photo by Steve Bird.
352 chapter 16 from monkeys to tarantulas: endless eccentricities