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152 IGUANA  •  VOLUME 14, NUMBER 3  •  SEPTEMBER 2007 ARIANO AND SALAZAR

With powerful limbs and claws, the Guatemalan Beaded Lizard (Heloderma horridum charlesbogerti) is well equipped to climb trees in
search of nestling prey. 

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The Helodermatidae belong to the reptile clade possessing
toxin-secreting oral glands (Fry et al. 2006). Lizards of this

family are specialized vertebrate nest predators (Pianka 1966).
The two species of Heloderma that comprise the Helodermatidae
are Heloderma suspectum and H. horridum (Campbell and Lamar
2004). The former is commonly known as the “Gila Monster,”
whereas the latter is known as the “Beaded Lizard,” “scorpion,”
or “sleeping baby” (Ariano 2003, Beck 2005). The coloration of
H. horridum is both cryptic and aposematic (Beck 2005). This
species reaches an average total length of about 650 mm (Beck
and Lowe 1991), and the tail is short in relation to the size of
the rest of the body (Álvarez del Toro 1982). The average weight
of an adult is around 800 g (Beck and Lowe 1991).

Four subspecies of H. horridum have been described: H. h.
horridum, H. h. exasperatum, H. h. alvarezi (Bogert and Martín
del Campo 1956), and H. h. charlesbogerti (Campbell and
Vannini 1988). Heloderma h. charlesbogerti, the Guatemalan
Beaded Lizard, represents an isolated and distinctive population
at the southern limit of the species’ distribution (Beck 2005).
Heloderma h. charlesbogerti differs from the other subspecies in
body proportions and color patterns (Campbell and Vannini
1988). Recent molecular studies suggest that this taxon (in con-
junction with H. h. alvarezi) may actually represent a distinct
species (Douglas et al. 2003).

The Guatemalan Beaded Lizard inhabits the dry forests of
the semiarid region of the Motagua Valley in eastern Guatemala
(Ariano 2003) at elevations of 300–900 m above sea level
(Campbell and Vannini 1988, Ariano 2003). Studies have
revealed that the species can be found along rocky hills with
steep slopes associated with dry forest vegetation including
Bucida macrostachya, Pereskia autumnalis, Moringa oleifera,
Licania hypoleuca, Cephalocereus maxonii, Bursera simarouba,
Leucaena diversifolia, and Bursera bipinata (Ariano 2003).

The holotype of H. h. charlesbogerti is in the vertebrate col-
lection of the University of Texas, Arlington (UTA R-15000),
and comes from the region of Espíritu Santo, El Jícaro, El
Progreso. Most of the paratypes also are in the UTA collection,

and others in the collection of vertebrates at the University of
Costa Rica (UTA R-15001–3, UTA R-18693, UCR 9602–3).
These were collected in 1984 and 1985 in the region of Gualán,
Zacapa, and from the region of Espíritu Santo in the Motagua
Valley (Campbell and Vannini 1988). The distribution of the
Guatemalan Beaded Lizard in Zacapa has been reduced drasti-
cally in recent years as a result of extensive loss of forest cover,
persecution by local people afraid of its venom, and extraction
from the wild for illegal trade (Ariano 2006).

Notes on the Distribution 
of the Endangered Lizard, Heloderma 

horridum charlesbogerti, in the Dry Forests
of Eastern Guatemala: An Application of
Multi-criteria Evaluation to Conservation

Daniel Ariano1,2 & Gilberto Salazar2

1Postgrado de Biología, Universidad de Costa Rica, San Pedro-San José, Costa Rica (darianosanchez@gmail.com)
2Asociación Zootropic, 12 calle 1-25 z. 10. Edif. Geminis 10, Torre Sur nivel 18, Of. 1801, Ciudad Guatemala, Guatemala

IGUANA  •  VOLUME 14, NUMBER 3  •  SEPTEMBER 2007 153HELODERMA HORRIDUM CHARLESBOGERTI

�

Guatemalan Beaded Lizards (Heloderma horridum charlesbogerti) in the
wild.

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Geographic Information Systems (GIS) have been useful
tools for identifying conservation priorities for species in chang-
ing landscapes (Bojorquez et al. 1995). Multiple criteria fre-
quently need to be evaluated as part of this process. Such proce-
dures are called “Multi-criteria Evaluation” (MCE; Carver 1991,
Eastman et al. 1995). MCE is most commonly achieved by
Boolean overlay. In this approach, all criteria are reduced to log-
ical statements of suitability and then combined by means of
one or more logical operators such as intersection (logical AND)
or union (logical OR) (Gutierrez and Gould 2000). This study
seeks to determine the potential distribution of H. h. charles-
bogerti in the semiarid region of the Motagua Valley in order to
prioritize conservation areas and develop better conservation
strategies for this population.

Methods
Study Site.—The analysis was conducted in the semiarid region
of the Motagua Valley (RSAVM) in northeastern Guatemala.
Dry forests are among the most endangered ecosystems in the
world (Janzen 1988). This region comprises about 200,000 ha
in the departments of El Progreso and Zacapa; it has the lowest
average annual rainfall in Central America (500 mm) and is
characterized by many endemic species (Nájera 2006).
Currently, the region is heterogeneous, characterized by agricul-
tural lands, grass lands, thornscrub, and very dry deciduous for-
est remnants, and includes zones of tropical thorn scrub, very
dry tropical forest, and dry tropical forest (Holdridge 1967). The
meteorological records of this area indicate that average maxi-
mum and minimum temperatures are 34.1 ºC and 17.9 ºC,
respectively, absolute maximum and minimum temperatures are
45.0 ºC and 4.4 ºC, average annual precipitation ranges from
400–1200 mm, and average relative humidity ranges from
60–80% (INSIVUMEH 2006). Elevations in the region range
from 180–900 m, with some peaks reaching 1,200 m. The area
is hot and is characterized by seasonal rains; but, in general, the
evaporation-transpiration is greater than the total rainfall (Nájera
2006). The rare combination of conditions occurring in
RSAVM has contributed to its designation as a “unique ecore-

gion of the world” in the classification developed by the WWF
(Dinerstein et al. 1995).

Multi-criteria Evaluation.—Seven digital maps were used for the
Multi-criteria Evaluation. These maps represented conditions of
forest cover, actual land use, geology, average rainfall, human
population centers, life zones, and slopes of the semiarid region
of the Motagua Valley in northeastern Guatemala. The maps
were in UTM coordinates with NAD 27 zone 16 datum in
raster system (MAGA 2002). 

The multi-criteria analysis used a Boolean approach of the
type “AND,” employing the macro-modeler interface of Idrisi
32 version I32.2. This means that only the pixels that have all
of the specific characteristics defined in the analysis will be cho-
sen as potential distribution pixels. The decision rules for this
MCE were based on the 2004–2006 collecting sites of H. h.
charlesbogerti. Categories chosen for each specific layer taking
into account these collecting sites were: deciduous forest, shrubs-
crops, and shrubs for the forest-cover layer; forest-shrubs for the
land-use layer; below 800 mm for the average rainfall layer;
PZM, Pi, and I categories for the geology layer; thorn scrub and
dry forest for the life-zone layer; and above15% for the slopes
layer. A buffer zone of 500 m was defined around each human
population center.

The final MCE (suitability map of potential distribution of
H. h. charlesbogerti) was constructed by overlaying all the
Boolean maps obtained for each layer, and then adding the con-
straint that the suitable areas not be within the human popula-
tion centers and the 500-m buffer zone. The area of the result-
ant polygons was measured and classified as: < 100 ha; > 100
but < 500 ha; > 500 but < 1000, and > 1000 ha. The patches
greater than 1000 ha were defined as the extant populations of
the species in its natural habitat.

The characteristics of collecting sites were obtained from
base maps (A, B), for which a Boolean transformation was
made, assigning value 1 to pixels with the desired characteristics,
and value 0 to pixels without those characteristics. Then, all the
resultant Boolean maps (C, D) were overlaid to obtain a final
potential distribution map (E). Map A represents forest cover
and map B represents hill slopes.

Finally, the suitability map was tested by overlaying the his-
torical collecting sites of H. h. charlesbogerti from 1984–2001.
These historical collecting sites were obtained by reviewing the
literature (Campbell and Vannini 1988, Ariano 2003) and the
data for specimens in local Guatemalan collections (both live
and preserved animals), such as that of the Natural History
Museum of the Universidad de San Carlos de Guatemala,
National Natural History Museum “Jorge Ibarra,” “La Aurora”
National Zoo, Zootropic Collection, and the Collection of
Universidad del Valle de Guatemala.

The accuracy of the suitability map was measured as the
percentage of historical locations predicted correctly by the suit-
ability map. Additionally, each area was visited and surveys were
distributed to local inhabitants asking them about the presence
of H. h. charlesbogerti in surrounding forests. As proposed by
Ariano (2003), they also were asked to distinguish the species
from a set of six photographs depicting the species Ctenosaura
similis, Coleonyx mitratus, Aspidoscelis managuae, Ctenosaura

154 IGUANA  •  VOLUME 14, NUMBER 3  •  SEPTEMBER 2007 ARIANO AND SALAZAR

Semiarid region of the Motagua Valley in northeastern Guatemala
(from Nájera 2006).

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IGUANA  •  VOLUME 14, NUMBER 3  •  SEPTEMBER 2007 155HELODERMA HORRIDUM CHARLESBOGERTI

palearis, Hemidactylus tuberculosus, and Heloderma horridum
charlesbogerti.

Results
The analysis generated a total of 60 polygons of potential dis-
tribution of H. h. charlesbogerti. Polygons were aggregated
according to geographic proximity in seven areas of potential

distribution of the species. These 60 polygons made up a total
area of about 25,108 ha of suitable habitat. Of these 60 poly-
gons, only 23 are in the > 100 but < 500 ha category, seven
areas are in the > 500 but < 1000 category, and only three areas
are > 1000 ha.

The resultant suitability map has an accuracy of 100%
because all historical collecting points (1984–2001) were within
the polygons predicted by the MCE analysis as potential habi-
tat for H. h. charlesbogerti. Also, surveys confirmed the presence
of the species in these seven major areas. For these reasons, we
believe that the resultant suitability map is a good predictor of
the actual distribution of the species according to actual land
use, forest cover, rainfall, slopes, and distance to human popu-
lation centers.

Area #3 contains the collecting sites of the holotype of the
species (UTA R-15000) and one paratype (UCR 9602)
(Campbell and Vannini 1988). Area #4 contains the more
recent collecting sites (Ariano 2003) and is the study site in
which six individuals of the species have been radio-tracked.
Data from these localities were the basis for determining condi-
tions and constraints established for the Boolean type MCE.
This area also contains the collecting sites of the six individuals
kept in captivity in the National Natural History Museum
“Jorge Ibarra,” the pair of individuals kept in the “La Aurora”
National Zoo, and one of the two individuals kept in captivity
in the Natural History Museum of Universidad de San Carlos
de Guatemala. Area #7 contains the collecting sites of five
paratypes (UTA-R-15001–3, UTA-R-18693, UCR 9603) and
the collecting sites of the individual in the Zootropic collection
and one of the individuals in the Natural History Museum of
Universidad de San Carlos de Guatemala.

According to the definitions of this study, we identified
only three extant populations of H. h. charlesbogerti. These pop-
ulations were in areas #4 (Cabañas-El Jícaro), #5 (San Jorge-
Zacapa), and #7 (Gualán-La Cartuchera-Los Jutes), all areas >
1000 ha of continuous potential habitat. The presence of H. h.
charlesbogerti in these areas was confirmed by the surveys and by
sightings in the wild by the authors.

Discussion
The three areas > 1000 ha are conservation priority areas for the
species. According to Ariano (2003), the most relevant threats
for the Guatemalan Beaded Lizard are loss of forest cover, illegal
extraction for collectors, and persecution by local people, who
consider it to be dangerous. As a means of mitigating these
threats, we propose the development of strong environmental
education programs for the human populations in the surround-
ing areas and promotion of the establishment of private natural
reserves within these areas. These actions may help to eliminate
the persecution of this species by local people and diminish the
loss of forest cover in the area.

The present study will help to prioritize the human com-
munities that need to be targeted by an educational program
promoting the conservation of the species. This is a way to opti-
mize the effectiveness of scarce resources (human and monetary)
available for developing any educational program in the area. It
also may be of great value in directing overall land conservation
efforts to ensure that the protected areas proposed for the region

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Schematic representation of Boolean MCE for determining the poten-
tial distribution of Heloderma horridum charlesbogerti in the semiarid
region of the Motagua Valley, Guatemala. A: Shades of gray represent
the different types of vegetative cover found in the semiarid region of
the Motagua Valley. A2: Gray areas represent portions of the same
region that match the vegetative cover suitable for Heloderma (decid-
uous forest, shrub-crops, or shrubs) based on Heloderma collection sites
from 2004–2006. B: Shades of gray indicate the degree of incline of
slopes in the semiarid region of the Motagua Valley. B2: Gray areas rep-
resent slopes that correspond to 2004–2006 Heloderma collection sites
(slopes > 15°). C: This map is the final product of the MCE showing
the entire potential distribution area of Heloderma horridum charles-
bogerti. Gray areas represent the cumulative overlay of all Boolean maps
for each of the selection criteria (forest cover, actual land use, geology,
average rainfall, human population centers, life zones, and slopes)
appropriate for Heloderma according to actual collection sites from
2004–2006.

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also preserve thorn scrub-very dry forest habitat and the extant
populations of H. h. charlesbogerti.

Excluding the areas < 100 ha from the analysis, the poten-
tial habitat for the species extends across only 17,534 ha. These
data illustrate the critically endangered status of this taxon in its
natural habitat, which is threatened by a considerable and ongo-
ing loss of forest cover. For these reasons, the implementation of
conservation policies and prompt short-term action are critical
to ensure the conservation of the Guatemalan Beaded Lizard. 

The historical distribution of H. h. charlesbogerti extended
across the dry forests of the semiarid region of the Motagua
Valley in northeastern Guatemala (Campbell and Vannini
1988), an area of about 200,000 ha (Nájera 2006). Presently,
only about 0.01% (25,108 ha) of the natural habitat remains.
Our data suggest that H. h. charlesbogerti is one of the most
endangered species in Guatemala.

All but one of the polygons of potential distribution were
along the southern bank of the Motagua River. This lends sup-
port for the hypothesis proposed originally by Stuart (1954) that
a Pacific subhumid corridor was the route by which H. horridum
gained access into the middle Motagua Valley. This hypothesis
has been considered the most plausible explanation for the pres-
ent distribution of H. horridum and many other xeric-adapted
species of reptiles in the Motagua Valley (Campbell and Vannini
1988). If true, we would expect that the major distribution of
H. h. charlesbogerti in the Motagua Valley would be along the
southern bank of the Motagua River, because the river has

proven to be an effective biogeographic barrier for other taxa
(Schuster et al. 2003).

The only way to ensure the conservation of this taxon in its
natural habitat is by protecting the last forest remnants harbor-
ing populations, and by implementing an educational program
for the human populations that inhabit the towns surrounding
these areas. The conservation efforts made along the southern
versant of the Motagua Valley have to be strengthened, because
almost every conservation effort so far has been made along the
northern versant of the Motagua Valley. Fortunately, these
actions are now in progress, principally through the efforts of the
Guatemalan NGO Zootropic and its partners, the International
Reptile Conservation Foundation and Zoo Atlanta (Ariano
2006). The governmental authority for biodiversity conserva-
tion, the National Council of Protected Areas (CONAP) also
has a strong interest in promoting the conservation of the last
dry forest remnants in the Motagua Valley, and in developing
national policies for the conservation of H. h. charlesbogerti. An
educational program was initiated recently by Zootropic, with
the financial support of the National Fund for Nature
Conservation (FONACON). These actions provide reasonable
hope for the conservation of the Guatemalan Beaded Lizard.
Another positive is the first successful captive breeding of this
species after years of failed attempts (Owens 2006).

Taking into account that most of the suitable habitat for
the species is made up of patches of forest < 100 ha in a highly
fragmented matrix of crops and cattle lands, the area should be
managed at a landscape level to ensure the conservation of the
species within its habitat (Bennet 2004, Ferrier et al. 2004).
Only with a combination of education, land protection, and
landscape management will the conservation of H. h. charles-
bogerti be ensured for the long term.

Acknowledgments
We thank the community in the Cabañas region, Zacapa,
Guatemala for their willingness to preserve this species for future
generations. Thanks to Luis Alvarado and Rodrigo Botrán of
Zootropic for supporting this project since its inception in 2002.
Thanks to Juan Aguilar, Priscilla Zamora (in memoriam),
Alejandro Muñoz, Blanca Arauz, Sabrina Amador, Ana
Guzmán, and Juan Palavicinni of the Universidad de Costa Rica
for their help in the early attempts to digitize the base maps.
CONAP provided permits to conduct this project. Thanks to
Zootropic, IRCF, Zoo Atlanta, and Universidad de Costa Rica
for support. Financial assistance for this part of the project was
provided by the German Academic Exchange Service (DAAD),
Zootropic, Idea Wild, and The Nature Conservancy. Special
thanks to Brad Lock (Zoo Atlanta) and John Binns (IRCF) for
their support of “Project Heloderma.” The present paper is part
of D. Ariano’s Master of Science thesis in the Department of
Biology of Universidad de Costa Rica.

Literature Cited
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Universidad del Valle de Guatemala.

156 IGUANA  •  VOLUME 14, NUMBER 3  •  SEPTEMBER 2007 ARIANO AND SALAZAR

Santa Rita Espiritu Santo El Rosario El Arenal Gualán Los JutesLa CartucheraZacapa

Motagua R
iver

Potential Distribution Areas

Cities, Towns, and Villages

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Historical Collecting Locations 
(1984—2001)

Actual Collecting Locations 
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Potential Distribution Areas

Cities, Towns, and Villages

Potential Distribution Areas 
greater than 1000 ha of suitable 
habitat.

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Historical and recent collecting localities and potential distribu-
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charlesbogerti) in the semiarid region of the Motagua Valley.

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395–406.

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Guatemalan Beaded Lizard habitat in the Motagua River Valley during winter and spring (left) and during the summer (right).

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This Guatemalan Beaded Lizard is part of the captive breeding program at Zoo Atlanta.

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R. Van Rompaey. 2004. Mapping more of terrestrial biodiversity for global
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S. Blair, M. Richardson, W. Hodgson, V. Ignjatovic, R. Summerhayes, and
E. Kochva. 2006. Early evolution of the venom system in lizards and
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Editorial Síntesis, Madrid.

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Guatemalan Beaded Lizard Elevated to 
CITES Appendix I

At the 12-day meeting of the 171 signatory nations of
the Convention on International Trade in Endangered

Species of Wild Fauna and Flora (CITES) in The Hague
(The Netherlands), the Guatemalan Beaded Lizard
(Heloderma horridum charlesbogerti) was elevated from
Appendix II to I, affording it a higher level of legal protec-
tion. The committee considering species proposals requires
a two-thirds vote of those present and voting to list a
species initially, transfer, or delist a species.

Appendix I lists species that are the most endangered
and threatened with extinction. CITES prohibits interna-
tional trade in these species except when the purpose of the
import is not commercial, for instance for scientific
research. In these exceptional cases, trade may be permit-
ted — provided that it is authorized by the granting of
both an import permit and an export permit (or re-export
certificate).

The Proposal Leading to the Change in Status
Summary: Heloderma horridum charlesbogerti is a subspecies
of the Beaded Lizard, a large, venomous lizard that occurs
in Mexico and Guatemala. This subspecies is endemic to
the Motagua Valley in eastern Guatemala, where it is
restricted to small, dispersed patches of forest in semi-arid
areas. The species H. horridum was categorized as
“Vulnerable” in the IUCN Red List in 1996. The range of
the subspecies has been reduced to 24,000 ha, its wild pop-
ulation is currently estimated at 170–250 individuals, and

it is regarded as threatened with extinction due to loss of its
habitat, collection for local and foreign collectors, the effects
of hurricanes, and persecution by local people, who fear it
because of its poisonous nature. A National Conservation
Strategy has been developed and will attempt to counteract
the threats. The subspecies has apparently been traded, both
nationally and internationally, and, although the numbers
are small, they are significant in relation to the total popu-
lation. Collection and trade in this subspecies is illegal in
Guatemala. Four subspecies of H. horridum are recognized,
and H. h. charlesbogerti differs from the others in various
details of morphology and coloration, making it relatively
easy to distinguish live animals when adult, although juve-
niles are said to be difficult to tell apart. Heloderma suspec-
tum, the only other species in the genus, is very distinctive.
Captive-breeding has so far been unsuccessful, despite many
attempts. Heloderma species have been included in
Appendix II since 1975. The proposal seeks to transfer the
population of the subspecies of Heloderma horridum charles-
bogerti from Appendix II to Appendix I.

Analysis: Heloderma horridum charlesbogerti appears to
meet the biological criteria for listing in Appendix I. Its
habitat has been severely reduced, it is restricted to dis-
persed patches of forest, the population is very small and
localized, and a population decline can be inferred from the
difficulty in finding the species currently, compared with
the 1980s.

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