The New Neotropical Companion

though they are not averse to sampling such delicacies
as bats, baby birds, and one another’s eggs.
Iguanas and ctenosaurs shift their diets from
primarily arthropods to primarily vegetation as they
increase in body size, a diet shift that may be related to
reptilian energetics and constraints of large size. Small
lizards can be active and successful in catching small but
scurrying prey, such as beetles and spiders. Large lizards
require more energy (simply because they are larger)
but actually need less energy per gram of body weight
(because large animals have slower metabolisms).
Perhaps they are not as well served by spending time
and energy trying to capture fast- moving insects, none
of which individually contain much energy. Plants don’t
move and they require little energy to “capture,” and

though plant material is harder to digest, more can be

swallowed at a single sitting. Thus, a vegetarian diet is

more optimal for a large lizard, presuming digestion of

the plant matter is not problematic to the creature. Even

some of the medium- size and large carnivorous lizards

do not pursue prey, perhaps because such pursuit would

expend more energy than would be contained in the

prey item. These animals sit and wait and then capture

any slow- moving arthropod (such as a caterpillar or

grub) that happens to blunder past.

The lizard family Teiidae includes the largest of the

South American lizards, the tegus (genus Tupinambis).

They superficially resemble Old World monitor lizards.

Four species range through South America. The

Argentine Black- and- white Tegu (T. merianae; plate

Plate 16- 80. This is a Helmeted Iguana. It is much more closely
related to basilisks, which it resembles, than to iguanas. Photo
by James Adams.

Plate 16- 81. This is a ctenosaur known as the Black Spiny-

tailed Iguana or Black Iguana (Ctenosaura similis). Like iguanas,

ctenosaurs are adept at climbing trees. Photo by Scott

Shumway.

Plate 16- 82. No, it’s not a T. rex. It is an Argentine Black- and-
white Tegu, found from southeastern Brazil through Uruguay
and Paraguay to Argentina. Photo by Dennis Paulson.

Plate 16- 83. The Common Tegu is called the Matte in Trinidad,

where this photo was taken. Photo by John Kricher.

354 chapter 16 from monkeys to tarantulas: endless eccentricities