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Notes on Heloderma suspectum
and Iguana tuberculata1

Pennoyer F. English

On April 2, 1923, the writer received a poisonous lizard,
Heloderrna suspectum, from Wheelock, Robertson County,

Texas. This village lies in the southeast part of the county on no
highway and about twelve miles from the nearest railroad. This
animal had been killed by a farmhand as it was crawling about
on his land, and was brought by a student to the department of
biology of the Agricultural and Mechanical College of Texas.
The finding of this reptile in Robertson County so far from its
native home is indeed interesting. Ditmars [“Reptiles of the
World,” 1922], Gadow [“Amphibia and Reptilia,” Cambridge
Natural History, Volume 8], Hegner [“College Zoology,” revised
edition, 1926], Hornaday [“The American Natural History,”
1904] and Pratt [“Manual of the Vertebrates of the United
States,” 1923], limit the distribution of these animals to Arizona,
New Mexico and northern Mexico. Only one other occurrence
of the Gila Monster in Texas is recorded in the literature avail-
able to the writer. Cope [“The Crocodilians, Lizards and Snakes
of North America,” Report U.S. National Museum, 1898] lists
a specimen taken at Fort McDowell, Texas. This single find was
referred to by Strecker [“Reptiles adn Amphibians of Texas,”
1915] who comments somewhat skeptically on the report and
states that he made careful search in favorable localities for these
reptiles, but failed to find them in Texas. Any attempt to explain

how this lizard found its way to Wheelock, some four or five
hundred miles from its native haunts, would be mere guesswork.

The writer has lately received from Mr. L. T. Hunter,
county agent, Childress County, Texas, another most interesting
find — the common Iguana, Iguana tuberculata. This reptile was
killed on a roadside near Childress and was sent to the
Agricultural and Mechanical College of Texas on December 20,
1926. Childress County lies close to the eastern border of the
Panhandle of Texas, touching the southwest corner of
Oklahoma. This find is even more remarkable than the former,
since the iguana was much farther from its native home — trop-
ical America. The specimen measures three feet, nine and one
half inches in length and apparently is only partly grown.
Gadow states that Iguana tuberculata attains a length of five or
six feet. Ditmars, Gadow, Hegner and Hornaday give the distri-
bution as Central and South America and the West Indies,
where it lives in trees. How such a reptile could find its way from
its tropical and arboreal habitat in the jungles to the almost tree-
less plains of Childress, Texas, is an interesting speculation.

Heloderma Suspectum, Automobile 
Tourists and Animal Distribution2

Charles T. Vorhies

In a note in SCIENCE, Mr. P. F. English [“Notes on
Heloderma suspectum and Iguana tuberculata,” SCIENCE,

Vol. LXVI, No. 1697, p. 37] records two instances of the find-
ing of large lizards at considerable distances from their known
native habitats. One of these occurrences is that of Heloderma
suspectum, the Gila monster, concerning which the author
remarks that “any attempt to explain how this lizard found its
way to Wheelock [Texas], some four or five hundred miles from
its native haunts, would be mere guesswork.” Concerning the
other, an Iguana tuberculata from Central America taken in
Texas, admittedly a still more difficult occurrence to explain, he
says, “How such a reptile could find its way from its tropical and
arboreal habitat in the jungles to the almost treeless plains of
Childress, Texas, is an interesting speculation.”

The present writer heartily agrees to the interesting character
of the speculation induced, but believes that an explanation for the
first, if not the second instance, may be offered which will be much
better than “mere guesswork.” Incidentally a new, or if not new, lit-
tle considered, factor in animal distribution may be given point.

254 IGUANA  •  VOLUME 14, NUMBER 4  •  DECEMBER 2007 HISTORICAL PERSPECTIVE

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

Two Early Reports of 
Intentionally Released Reptiles

1 Originally published in Science, New Series, Vol. 66, No. 1697, 8
July 1927, p. 37.

2 Originally published in Science, New Series, Vol. 68, No. 1756, 24
August 1928, pp. 182–183.

Gila Monsters (Heloderma suspectum) showing up far from their orig-
inal range in the 1920s was attributed to intentional transport and
release by humans.

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IGUANA  •  VOLUME 14, NUMBER 4  •  DECEMBER 2007 255HISTORICAL PERSPECTIVE

During the course of a dozen years in my present location
I have received from interested and curious persons many spec-
imens of the peculiar or unique animals of the southwest; and
there have passed through my hands, mainly from these sources,
probably nearly one hundred Gila monsters. During that period
of time, though my work has taken me afield frequently, I have
in person come across barely a half dozen of these conspicuous
and not very swift lizards. This indicates, first, the extent to
which people gather up specimens of animal life that excite their
curiosity, and transport them in a spirit of helpfulness, curiosity
or cupidity. (I have been asked to pay ten dollars for a very ordi-
nary Gila monster, and been solemnly assured that they were
worth one hundred dollars.) Secondly, the modern auto tourist
is likely to tire of and release his “specimen” unless he can dis-
pose of it to advantage. I have been the recipient of two
Helodermas, each of which had been carried for some time by
auto touring parties, and for distances of not less than two hun-
dred miles. Further, such a specimen is frequently carried teth-
ered somewhere on the outside of the car by an insecure noose
about its neck or leg. Tourists in this region often express a desire
to take a “Gila” “back home,” anywhere from five hundred to
fifteen hundred miles from here — and no doubt many of them
attempt to do so. A certain dealer in live animals sells surprising
numbers of them for this very purpose.

The finding of the specimen in Texas is no surprise to me.
It seems much more certain than “guess work” to assume that
such an animal, or any interesting animal of readily transportable
size, found even hundreds of miles from its native home, has
been carried most of the distance by rail or auto, especially the
latter. The Heloderma mentioned might easily have wandered
from the nearest main highway, even though the distance be con-
siderable, for this lizard is tenacious of life, and that locality would
not, I believe, be a particularly unfavorable environment for it.

The principles involved in the foregoing statements have
many and various illustrations, as every inspector at a horticul-
tural inspection station on a main auto highway in the south-
west can testify. The auto tourist carries everything interesting
from where he finds it to some other place; anything from a
“horned toad” to an entire cotton plant, leaves, bolls, boll wee-

vils and all. The Iguana tuberculata record is, to be sure, some-
what less likely to be the result of transfer by auto, but not
unlikely to have come up by train. I have now a live Iguana sp.
which recently arrived in Tucson in a bunch of bananas by rail
from the west coast of Mexico. A few years ago I was the recip-
ient of a live five and one-half foot Boa imperator, picked up by
an autoist just beyond the border town of Nogales, Sonora. This,
I should judge, came up from Central America nearly to the
United States by train, thence it certainly came another seventy
miles by auto. Mr. Roy McCain, of Tucson, relates that, while
hunting a few miles northwest of Pantana, a station about thirty
miles east of Tucson, in the foothills of the Rincon Mountains,
he met a large lizard which he killed with a stick. This measured
three feet in length and must have been an Iguana sp., though
unfortunately it was not saved. This was in October, 1927.

I have now alive in my laboratory an opossum, carried into
this new (and probably unfavorable) environment from
Arkansas. Its captor chanced to tire of it just at this point, but
might equally well have elected to turn it loose in some favorable
looking spot in the state — or in California. It is known that
opossums have previously been released in this region. Arizona
(likewise California) has a cordon of horticultural inspectors sta-
tioned at strategic points for intercepting and inspecting autos
coming into the state. The findings of these inspectors, plus the
other instances cited, have served to emphasize for us here the
possibilities of auto traffic as a factor in animal distribution in a
manner which, perhaps, has not come forcibly to the attention
of biologists in many other states. The cotton plant incident is a
fact from the experiences of the inspectors.

Editor’s Remarks
Invasive species are a major problem that conservation
biologists face on a regular basis. In recent years, we
have been seeing more and more reports of reptiles
and amphibians appearing far from their natural
ranges. Traditionally, introduced species were thought
to arrive in “foreign” destinations mostly by accident.
A recent note (2006. Iguana 13:272–277) described
an attempt to prevent such arrivals on Guana Island
in the British Virgin Islands. Recent research, how-
ever, has shown that a large number of these invasives
are intentionally released by pet owners and others.
The two brief reports that follow clearly show that
this is not a new phenomenon: Some eighty years ago,
large lizards and snakes were being noted hundreds of
miles from their native ranges. P.F. English found this
confusing, but C.T. Vorhies identified people as the
primary vector long before others became aware of the
issue. These fascinating early notes are a strong
reminder to never release a captive animal — we now
unerstand the potentially disastrous consequences of
such irresponsible behavior.

Gad Perry
Texas Tech University

Although Green Iguanas (Iguana iguana) have been widely introduced
in recent years, their appearance in Texas in the 1920s was difficult to
explain.

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