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T
he Galápagos Islands are a world unto
themselves. The majority of the plants and
animals there are found nowhere else.
Among the animals, the reptiles play a very

important role, ecologically replacing the mam-
mals that are absent from the islands, especially the
herbivores. Only a few species are native, but each
is (or was only a few decades ago) exceedingly
abundant. Of particular interest are the iguanian
squamates and, of those, two exceptionally
unusual species stand out. These are easily distin-

guished from related iguanas by examining their
dentition, the shape and scalation of their heads,
the strength of the head skeleton, and the lack of
a dewlap. Both species agree in general body form
and they also demonstrate some behavioral simi-
larities; neither of the two is particularly mobile
and both are vegetarian, although they consume
very different plants. In fact, one lives on land and
the other is completely dependent upon water.
Unique among squamates, the latter, which can
accurately be called a marine animal, feeds exclu-
sively on aquatic plants.

The Sea-lizard, as we are wont to call it,
Amblyrhynchus cristatus Bell [translator’s note:
Thomas Bell was an Englishman who named
many amphibians and reptiles in the 19th century],
is the only representative of its genus. It is a very
large iguana. Of the total length of 135 cm, 80 cm
is tail. Weight can reach 12 kg. The short, broad
head slopes steeply to each side, tapers toward the
front, and the profile arches rapidly and sharply

from the forehead to
the blunt snout. To
best characterize the
beast, I have taken the
following information
from Steindachner
[Franz Steindachner
was an Austrian ichthy-
ologist and herpetolo-
gist associated with the
Vienna Museum of
Natural History from
1860 until his death in
1919], who wrote a
treatise on the squa-
mates of the Galápagos
Islands [published in
1876]: The entire top
of the head is covered
in mosaic fashion by

H I S T O R I C A L  P E R S P E C T I V E S
145IGUANADecember 2003

Iguanas of the Galápagos Islands1

Franz Werner, 
with extensive quotations from Charles Darwin

Sea-lizard, Amblyrhynchus
cristatus Bell. 1/6 natural size.

1 Excerpted and translated from Franz Werner (1913. Die
Lurche und Kriechtiere von Alfred Brehm. Zweiter Band:
Kriechtiere (Schuppenkriechtiere), pp. 86–92 + table “Lizards
V,” no. 3. In O. z. Strassen (ed.), Brehms Tierleben.
Allgemeine Kunde des Tierreichs. 4th ed. Bibliographisches
Institut, Leipzig and Wien. Translated by R. Powell. Quotes
from Darwin were not translated from Werner’s text, but
instead were taken directly from C. Darwin (1845. The
Voyage of the Beagle. 2nd ed.). Some excerpts omitted by
Werner are included here.



many quadrangular (usually) or six-sided scales of
varying sizes; the largest are conical or even
pointed and lie primarily toward the front of the
head, whereas the smallest form the supraocular
shields. The lateral but relatively highly situated,
egg-shaped nares are angled from low in front to
high in back, and are surrounded by an elevated
leathery rim, which in turn is surrounded by small
scales. Nine to ten five-sided plates form the upper
lip and 12–13 four-sided plates make up the lower
lip. An arc-like band of keeled scales extends from
the region under the eye to the temple, whereas
the underside of the head is covered by small
rounded scales. The egg-shaped tympanum is
embedded in a raised border of tubercular scales.
The skin of the throat and neck is more or less
loosely attached and forms a distinct gular fold.
The body is generally robust, and the dorsal crest
is continuous from the neck to the tip of the tail,
although indentations mark the transitions from
neck to body and body to tail. The scales of the
body are distinguished by size and location. Dorsal
scales are all keeled, lateral scales are tuberculate,
whereas the ventral scales are completely smooth.
The long tail has a thick base but becomes dis-
tinctly compressed laterally toward the tip, in
essence forming a paddle or fin. The tail is covered
with keeled scales, like those on the back, arranged
in distinct rings. The limbs are short and stocky.
The third and fourth toes are of equal length and

are longer than the
others. All are con-
nected by a small web
and equipped with
powerful, sharp, and
slightly arched claws.
The thick tongue is as
wide as the mouth.
The long, large teeth
are serrated and
attached to the outer
fold of the deeply
grooved jaws. Each
upper jaw bears 22–25
teeth, each lower jaw
20–24, of which 6–8
are similar to the lateral
teeth and are on the
intermaxilla. The small
and not particularly
numerous teeth on the

pterygoid and sphenoid are easily displaced.
Color and pattern vary by age. Young Sea-

lizards have numerous light gray flecks on both
sides of the head, the chin, and on the sides of the
body. These may reduce the black ground color to
net-like reticulum. On the back, alternating dirty
gray and black bands of flecks produce a more or
less regular pattern of crossbands. The upper and
lateral sides of the limbs are either punctuated with
small gray flecks or larger gray spots. The chin is a
dark dirty gray, the throat is black, and the belly a
dirty yellow-brown. The digits, the axilla and
groin, and the distal half of the tail are black. The
dorsal crest is variably yellow or gray with black
bands. Occasional individuals are entirely black.

Sea-lizards are phenomenally abundant on the
Galápagos Islands. Darwin found them on all of
the islands he visited; Steindachner found them on
Albemarle, Charles, James, and Jervis islands, with
those on the latter in particularly large numbers
and including some individuals of imposing size;
W.E. Cookson [an English explorer] also found
them on Abingdon Island. Corresponding to their
habits, these lizards restrict themselves to the rocky
shorelines and, according to Darwin’s observa-
tions, are not to be found more than 10 paces
from the water’s edge.

Darwin noted: “They are occasionally seen
some hundred yards from the shore, swimming
about; and Captain Collnet, in his Voyage, says,

146 IGUANA Volume 10, Number 4

Granular-head, Conolophus subcristatus Gray. 1/5 natural size.



‘They go to sea in herds a-fishing, and sun them-
selves on the rocks; and may be called alligators in
miniature.’ It must not, however, be supposed that
they live on fish. When in the water this lizard
swims with perfect ease and quickness, by a ser-
pentine movement of its body and flattened tail —
the legs being motionless and closely collapsed on
its sides. A seaman on board sank one, with a
heavy weight attached to it, thinking thus to kill it
directly; but when, an hour afterwards, he drew up
the line, it was quite active. Their limbs and strong
claws are admirably adapted for crawling over the
rugged and fissured masses of lava, which every-
where form the coast. In such situations, a group
of six or seven of these hideous reptiles may often-
times be seen on the black rocks, a few feet above
the surf, basking in the sun with outstretched legs.

“I opened the stomachs of several, and found
them largely distended with minced sea-weed
(Ulæ), which grows in thin foliacious expansions of
a bright green or a dull red colour. I do not recol-
lect having observed this sea-weed in any quantity
on the tidal rocks; and I have reason to believe it
grows at the bottom of the sea, at some little dis-
tance from the coast. If such be the case, the object
of these animals occasionally going out to sea is
explained. The stomach contained nothing but the
sea-weed. Mr. Bynoe, however, found a piece of a
crab in one; but this might have got in accidentally,
in the same manner as I have seen a caterpillar, in
the midst of some lichen, in the paunch of a tor-
toise. The intestines were large, as in other herbiv-
orous animals. The nature of this lizard’s food, as
well as the structure of its tail and feet, and the fact
of its having been seen voluntarily swimming out
to sea, absolutely prove its aquatic habits; yet there
is in this respect one strange anomaly, namely, that
when frightened it will not enter the water. Hence

it is easy to drive these lizards down to any little
point overhanging the sea, where they will sooner
allow a person to catch hold of their tails than jump
in the water. They do not seem to have any notion
of biting; but when much frightened they squirt a
drop of fluid from each nostril. I threw one several
times as far as I could, into a deep pool left by the
retiring tide; but it invariably returned in a direct
line to the spot where I stood. It swam near the
bottom, with a very graceful and rapid movement,
and occasionally aided itself over the uneven
ground with its feet. As soon as it arrived near the
edge, but still being under water, it tried to conceal
itself in the tufts of sea-weed, or it entered some
crevice. As soon as it thought the danger was past,
it crawled out on the dry rocks, and shuffled away
as quickly as it could. I several times caught this
same lizard, by driving it down to a point, and
though possessed of such perfect powers of diving
and swimming, nothing would induce it to enter
the water; and as often as I threw it in, it returned
in the manner above described. Perhaps this singu-
lar piece of apparent stupidity may be accounted for
by the circumstance, that this reptile has no enemy
whatsoever on shore, whereas at sea it must often
fall prey to the numerous sharks. Hence, probably,
urged by a fixed and hereditary instinct that the
shore is its place of safety, whatever the emergency
may be, it there takes refuge.” Darwin was unable
to address reproduction in these animals.

Steindachner visited the Galápagos Islands in
1872 and, like Dampier and Darwin before him,
saw thousands of Sea-lizards. “When my fellow
traveler, Pitkins, saw a large number of these
hideous animals, he ran into the midst of the
densely packed mass. When I visited the same site
shortly thereafter and again after about an hour, it
was completely void of lizards. They had all fled

into the sea and proba-
bly had sought out
another, more distant
refuge. My experience,
also on James and
Jervis islands, indicated
that the sea-lizards,
although sluggish and
awkward in their
movements and easily
captured without resis-
tance, do these days
seek the sea to escape

147IGUANADecember 2003

Granular-head, Conolophus subcristatus Gray. 1/8 natural size. Photograph by W.P. Dando,
F.Z.S. – London.



potential threats when they notice enemies in the
vicinity — instead of, as earlier, returning stub-
bornly to the same site on shore. On calm days,
one frequently encounters these lizards long dis-
tances from shore swimming and diving with ease
and surprising speed. Their movements in water
resemble those of a snake. Only the head is emer-
gent while swimming, and the limbs are adpressed.
On Jervis Island, I found them only in the imme-
diate vicinity of the sea, usually in herd-like masses
of 100–150 packed into small spaces on the rough
and rugged lava. On James Island, I encountered
only a few individuals considerably above the shore
along the edges of small, overgrown cavities in the
rocks that might serve as nesting sites. The stom-
ach and intestine, as Darwin already mentioned,
are without exception stuffed with foliacious green
or dull-red algae.”

The second lizard of the
Galápagos Islands, which we will call
the Granular-head, differs distinctly
from the Sea-lizard in overall stature
and in the absence of pterygoid teeth
in adults. Overall, these are even
more plump and ponderous.
Restricted to dry land, they lack web-
bing between the short toes that ter-
minate the stout limbs. The tail also is
shorter and only slightly compressed,
oval in cross-section and almost with-
out a crest. In contrast, the neck is
considerably longer and bears longi-
tudinal folds of skin on its underside.
The head also is more elongate, con-
sequently less distinctly arched in pro-
file and sloping less steeply to the
sides. For all of these reasons,
Steindachner agreed with those
researchers who considered the
Granular-head, Conolophus subcrista-
tus Gray [John Edward Gray was a
19th century English naturalist and is
widely regarded as the founder of the
herpetological collections at the
British Museum], to be a representa-
tive of a unique genus (Conolophus
Fitz. [“Fitz. refers to Leopold
Fitzinger, a prolific Austrian zoologist
who wrote Neue Classification der
Reptilien in 1826 and Systema
Reptilium in 1843]).

In terms of color, the Granular-head differs
considerably from the Sea-lizard. The head is a
more or less lively yellow, the back near the crest is
brick- or rust-red, and, in rare cases, the body
sports faint, alternating yellowish and reddish-
brown crossbands. Down the sides, the reddish-
brown color gives way to a dirty, dark brown.
Here and there, one may notice dots or small
black flecks with indistinct edges. The belly is dark
yellow with a tinge of reddish-brown. The upper
and outer surfaces of the forelimbs are reddish, the
hindlimbs are brownish yellow, but the claws and
toes are black. These lizards reach a length of 107
cm, of which 54 cm is tail.

Darwin observed Granular-heads in the cen-
tral islands of the Galápagos Archipelago,
Albemarle, James, Barrington, and Indefatigable,
where they occupy both the higher, moister areas

148 IGUANA Volume 10, Number 4

Illustration by John Binns.



and the lower, infertile regions, where they actu-
ally are more common. Darwin noted: “I cannot
give a more forcible proof of their numbers, than
by stating that when we were left at James Island,
we could not for some time find a spot free from
their burrows on which to pitch our single tent.
Like their brothers the sea-kind, they are ugly ani-
mals, of a yellowish orange beneath, and of a
brownish red colour above: from their low facial
angle they have a singularly stupid appearance.
They are, perhaps, of a rather less size than the
marine species; but several of them weighed
between ten and fifteen pounds. In their move-
ments they are lazy and half torpid. When not
frightened, they slowly crawl along with their tails
and bellies dragging on the ground. They often
stop, and doze for a minute or two, with closed
eyes and hind legs spread out on the parched soil.

They inhabit burrows, which they sometimes
make between fragments of lava, but more gener-
ally on level patches of the soft sandstone-like tuff.
The holes do not appear to be very deep, and they
enter the ground at a small angle; so that when
walking over these lizard-warrens, the soil is con-
stantly giving way, much to the annoyance of the
tired walker. This animal, when making its burrow,
works alternately the opposite sides of its body. One
front leg for a short time scratches up the soil, and
throws it towards the hind foot, which is well placed
so as to heave it beyond the mouth of the hole.
That side of the body being tired, the other takes up
the task, and so on alternately. I watched one for a
long time, till half its body was buried; I then
walked up and pulled it by the tail; at this it was
greatly astonished, and soon shuffled up to see what
was the matter; and then stared me in the face, as
much as to say, ‘What made you pull my tail?’

“They feed by day, and do not wander far
from their burrows; if frightened, they rush to
them with a most awkward gait. Except when run-
ning down hill, they cannot move very fast, appar-
ently from the lateral position of their legs. They
are not at all timorous: when attentively watching
any one, they curl their tails, and, raising them-
selves on their front legs, nod their heads vertically,
with a quick movement, and try to look very
fierce: but in reality they are not at all so; if one just
stamps on the ground, down go their tails, and off
they shuffle as quickly as they can. I have fre-
quently observed small fly-eating lizards, when
watching anything, nod their heads in precisely the

same manner; but I do not at all know for what
purpose. If this Amblyrhynchus [in Darwin’s day,
both Galápagos iguanas were placed in the genus
Amblyrhynchus] is held and plagued with a stick, it
will bite it very severely; but I caught many by the
tail, and they never tried to bite me. If two are
placed on the ground and held together, they will
fight, and bite each other till blood is drawn.

“The individuals, and they are the greater num-
ber, which inhabit the lower country, can scarcely
taste a drop of water throughout the year; but they
consume much of the succulent cactus, the
branches of which are occasionally broken off by the
wind. I several times threw a piece to two or three
of them when together; and it was amusing enough
to see them trying to seize and carry it away in their
mouths, like so many hungry dogs with a bone.
They eat very deliberately, but do not chew their
food. The little birds are aware how harmless these
creatures are: I have seen one of the thick-billed
finches picking at one end of a piece of cactus
(which is much relished by all the animals of the
lower region), whilst a lizard was eating at the other
end; and afterwards the little bird with the utmost
indifference hopped on the back of the reptile.

I opened the stomach of several, and found
them full of vegetable fibres and leaves of different
trees, especially of an acacia. In the upper region
they live chiefly on the acid and astringent berries
of the guayavita, under which trees I have seen
these lizards and huge tortoises feeding together.
To obtain the acacia-leaves they crawl up the low
stunted trees; and it is not uncommon to see a pair
quietly browsing, whilst seated on a branch several
feet above the ground. These lizards, when
cooked, yield a white meat, which is liked by those
whose stomachs soar above all prejudices.
Humboldt [Alexander von Humboldt, a famous
German naturalist whose explorations of South
America thrilled Europe and inspired Darwin] has
remarked that in intertropical South America, all
lizards which inhabit dry regions are esteemed del-
icacies for the table. The inhabitants state that
those which inhabit the upper damp parts drink
water, but that the others do not, like the tortoises,
travel up for it from the lower sterile country. At
the time of our visit, the females had within their
bodies numerous large, elongated eggs, which
they lay in their burrows: the inhabitants seek
them for food.”

149IGUANADecember 2003




