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CUADERNOS DE INVESTIGACIN
INSTITUTO DE INVESTIGACIONES INTERDISCIPLINARIAS
UNIVERSIDAD DE PUERTO RICO EN CAYEY
Human Ecology of a Species Introductio
Interactions between Humans and
Introduced Green Iguanas in a
Puerto Rican Urban Estuary
Carlos G. Garca-Quijan
Toms A. Carlo-Jogl
Cuaderno 13
Ao 2010
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En la serie Cuadernos de Investigacin del Instituto de InvestigacionesInterdisciplinarias de la Universidad de Puerto Rico en Cayey se presentarnresultados parciales y preliminares de algunas de las investigacionesauspiciadas por el Instituto, versiones preliminares de artculos, informestcnicos emitidos por nuestras(os) investigadoras(es) as como versiones finales
de publicaciones que, por su naturaleza, sean de difcil publicacin por otrosmedios.
Los(as) autores(as) son responsables por el contenido y retienen los derechosde publicacin sobre el material contenido en estos Cuadernos.
Copias de los Cuadernos se pueden obtener solicitndolas por telfono, porcorreo regular o por correo electrnico al Instituto. Tambin se pueden descargarde nuestra pgina electrnica en formato pdf.
Instituto de Investigaciones InterdisciplinariasUniversidad de Puerto Rico en Cayey205 Ave. Antonio R. BarcelCayey, PR 00736
Tel. 787-738-2161, exts. 2615, 2616Fax 787-263-1625Correo electrnico: [email protected] web: http://webs.oss.cayey.upr.edu/iii/
Diseo de Portada: Prof. Harry HernndezEncargado de la serie de cuadernos: Dr. Errol L. Montes PizarroDirectora del Instituto: Dra. Isar P. GodreauDirectora Auxiliar: Sra. Vionex M. Marti
CGQ
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Human Ecology of a Species Introduction:
Interactions between Humans and Introduced
Green Iguanas in a Puerto Rican Urban Estuary
By:
Carlos G. Garca-Quijano1,2 and Toms A. Carlo-Joglar3
1Assistant Professor, Department of Sociology and Anthropology,
University of Rhode Island2Research Associate, Instituto de Investigaciones Interdisciplinarias,
Universidad de Puerto Rico-Cayey3Assistant Professor,Department of Biology, Pennsylvania State University
With the collaboration of Mario Flores-Mangual, Jorge Bauz,
Hctor Martnez, Natalia Rodrguez, and Javier Arce
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TABLE OF CONTENTS
Acknowledgements.................................................................................................... 1
Introduction................................................................................................................ 2
Species Introductions are Human Ecological Phenomena ........................................ 3
Brief history of the green iguana introduction........................................................... 11
Iguanas were significantly aggregated towards the borders of the mangrove forests 16
There was a spatial association between human settlements and iguana populations 17
Structured intercept interviews with SBJE recreational and subsistence resource users 22
Attitudes towards exotic species and the green iguana ............................................. 23
Conclusion ................................................................................................................. 34
References.................................................................................................................. 36
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Acknowledgements:
We would like to thank Mario Flores-Mangual, Jorge Bauz, Natalia Rodrguez,
Hctor Martnez, Augusto Carvajal, Javier Arce, and Emmanuel Rivera for their help
during research design, data collection, data analysis, and dissemination. We also thank
Hilda I. Llorns for useful editorial advice and suggestions, as well as Isar Godreau and
Jorge Bauz for financial and logistical support. The fieldwork reported herein was made
possible by a grant from the San Juan Bay Estuary Consortium to T. Carlo-Joglar, C.
Garca-Quijano and M. Flores-Mangual; and from a seed-money grant from the Instituto
de Investigaciones Interdisciplinarias, UPR-Cayey, to C. Garca-Quijano. Responsibility
for any shortcomings of this report rests with the authors C. Garca-Quijano and T. Carlo-
Joglar. Finally, we would like to thank everyone who took time from their busy schedules
to talk to us during our field interviews.
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Introduction
Non-indigenous, introduced species and their impact on invaded ecosystems are a
worldwide concern (Vitousek et al. 1996; Temple 1990; Pfieffer and Voeks 2009). By
some accounts, introduced species pose one of the greatest current threats to the global
environment, similar in magnitude to industrial pollution and global warming. Although
globalization, and the increased interconnectedness of human populations and economies
have certainly accelerated species introductions and associated alarm by people and
governments in the last few decades, concern for introduced species is not new: spirited
debates about introduced and exported plants and animals have been raging for over a
century in both sides of the Atlantic Ocean (Coates 2007; Elton 1958; Howard 1897).
When a species of organism is introduced to a new geographic area, it becomes
subject to interactions with the biotic and abiotic components of the local ecosystem,
including humans who live in the area. The nature of these interactions will determine
whether the species will become established or not, and whether the new species will
have a minor or major impact in the structure of the host ecosystem. In particular,
interactions with humans will also determine whether the new species will be classified
as beneficial, harmless, a nuisance, or hazardous, and thus what course of action and
policy will be taken in respect to the introduced species. In other words, the introduced
species interaction with the dominant species in the ecosystem humans will be crucial
to the trajectory and the fate of the introduced species and its surrounding ecosystem.
This paper reports results of ongoing interdisciplinary research about the
interactions between people and an introduced large arboreal lizard (the green iguana,
Iguana iguana) in the San Juan Bay Estuary (SJBE), located in the Caribbean island of
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Puerto Rico. Green iguanas have become established in Puerto Ricos coastal and
riparian forests since having been introduced to the island by pet enthusiasts beginning as
early as the 1970s. As evidenced by a large amount of Puerto Rican newspaper press
dedicated to the subject, the green iguana, along with the small Indian mongoose
(Herpestes javanicus), the Patas monkey (Erythrocebus patas), the rhesus macaque
(Macaca mulatta), and the spectacled cayman (Caiman crocodilus) have become one the
most talked and written-about new exotic additions to Puerto Ricos vertebrate fauna
(notwithstanding that feral domestic cats, dogs, and rats, all of which have become feral
in Puerto Rico, each vastly outnumber and out-impact any other introduced vertebrate
species).
Species introductions and their impacts in populated coastal areas are multi-
dimensional phenomena that transcend traditional scientific discipline boundaries. The
research presented herein is part of an ongoing interdisciplinary research project that
combines ecological and anthropological approaches to characterize the green iguanas
impact on and Puerto Ricos estuaries and coastal forests. The ecological and
sociocultural aspects of the green iguana introduction to Puerto Ricos coastal forests are
intrinsically linked. An increased understanding of the origins, causes, effects, impacts,
and future trajectories of human-mediated species introductions must come from
collaborations between the social and ecological sciences.
Species Introductions are Human Ecological Phenomena
A species introduction is generally defined as the human-mediated move of floral
or faunal species to an ecosystem or landscape where the species would not be present
were it not for human intervention (Carlton 2001). Although the vast majority of research
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regarding species introductions is done in the biological sciences, species introductions
are by definition a human ecological phenomena, tied in origins, proximate and distal
causes, effects, and outcomes to human activities, cultural values, and socioeconomic
factors.
The fossil, archaeological, and historical record shows that when Homo sapiens
move from place to place, they almost invariably transport other fauna and flora species
with them (Reitz and Wing 2008:116; Vermeij 2005). The earliest recorded non-native
species introduction by humans is the introduction of the gray cuscus (a small marsupial,
Phalangys orientalis) from New Britain to New Ireland in the Papua New Guinea
Archipielago, about 19,000 years ago (Allen and White 1989; Grayson 2001; Flannery
and White 1991). Tools, clothing, and transportation vessels provide more places where
other organisms can catch a ride with moving humans. The domestication of plants and
animals meant that traveling humans would come to depend on as well as develop
whole subsistence/cultural systems about certain plant and animal species. These
species of plants and animals would likely be transported by people when they moved to
new areas, whether already populated or not. Introduced agricultural species that are
important for human subsistence can become iconic or sacred species in the host location,
even after a relatively short time since introduction (Fowler 2005).
The long-standing association between people and the plants and animals they
depend on for food, tools, shelter, or companionship is so strong that changes in faunal
assemblages (the presence of novel or newly abundant organisms in the archaeological
record) are often used by archaeologists as proxies to reconstruct the movements of
people across space and time. For example, direction and timing of human settlements in
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the Caribbean Archipielago by early island settlers have been partly traced by looking at
the animals and plants that the settlers brought with them as they moved from the
American continental masses to the islands and between islands (Newsom and Wing
2004; Rouse 1992; Wilson 1997; Wing 1989). Similar lines of evidence have been used
as evidence to reconstruct people movements in the insular Pacific and Indian Oceans
(Nowak 1999; Crosby 1986; Reitz and Wing 2008:317). However, because species also
migrate and move by non-anthropogenic forces, it is often hard to tell whether novel
species have appeared in a location by human mediation or by non-human processes
(Wing 1993).
As the world has become more connected during the last 5 centuries (i.e. more
people and goods have moved more between previously unconnected regions of the
world), species introductions by people have accelerated exponentially. Agricultural and
animal husbandry species such as wheat, maize, tomatoes, chickens, cattle, horses,
sheep/goats and pigs have been propagated through most of the range of human
habitation. The same has happened with animal companions/workers such as dogs and
cats and also with unwanted pests or hitchhikers such as rats and house mice, which have
traveled with humans to virtually every place that humans have settled-except possibly
the Artic Circle. Thus whether a species introduction happens and whether it will happen
again on the future often depends on socioeconomic factors extraneous to the workings of
local ecosystems (and even local societies). For example, centuries ago the contact
between the Old and New Worlds propelled hundreds or thousands of species in both
directions of the Atlantic. More recently, the Green and Blue Revolutions have exported
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economically important species (as well as many of their symbionts) to worldwide
distributions.
The exotic animal trade is another source of the translocation of species to foreign
locales. Exotic animals have long been commodities and symbols of wealth, power, and
prestige. Trade in exotic animals for companionship, entertainment, or prestige is
millennia old: for example, one of ancient Egyptian King Ptolemy iis most prized
possessions was a live polar bear and which led precessions through the streets of third
century B. C. Alexandria (Bruemmer 1998). Marco Polo described how Kublai Khan
traveled with an extensive raptor collection that featured falcons and gyrfalcons from
several continents (Bruemmer 1998). This is not confined to the Old World: there is
prehistoric evidence of a large, organized trade in macaws (Ara sp.) from tropical
(southern) Mexico to the American Southwest that included extensive keeping and
breeding facilities along the way a trade that continues today- (Hargrave 1970; Minnis
et al. 1993). The modern exotic pet trade is a huge worldwide enterprise that involves
people from all socioeconomic backgrounds. This trade is the source of several high-
profile species introductions such as Burmese pythons in Florida and caymans in northern
Puerto Rico, as well as (at least partly) the green iguanas.
Social science work on species introductions has revealed that peoples
perspectives and attitudes towards introduced species (and whether they are considered as
a natural part of the ecosystem or not) vary depending on the specific impacts that the
species has on their livelihoods enjoyment of the landscape and their sense of
environmental aesthetics, phylogenetic bias, knowledge of and experience with their local
ecosystems, (Pfeiffer and Voeks 2008; Fortwanlger 2009; Hall 2009; Weeks and Packard
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2009). We found during this research that another source of variation can be the extent to
which any nationalistic pride sentiments extend to peoples attitudes and values towards
their environment-as is the case in Puerto Rico and much of Latin America-.
Only a tiny minority of the plants or animals that are introduced to a new
ecosystem are able to produce permanent populations; some of them however can
explode and radically impact the host ecosystem over time. Some introduced plants and
animals have been reproducing in their host ecosystem for so long that most people who
live there do not recognize them as introduced by people: to them the introduced species
is a part of their surrounding ecosystem as much as any other local species.
Anthropologists have provided important insights on this: For example, Fortwangler
(2009) documented how residents of the island of St. John, USVI, regarded long
introduced wild donkeys as part of their island ecosystem; these island residents were in
turns surprised and dismayed when the National Park Service started a campaign of
eradication that included hunting down and killing donkeys. Similarly, Weeks and
Packard (2009) report that while park rangers and scientists working at the Beg Bend
National Park in Texas tend to view introduced feral hogs as unwanted invasive species,
many long-time residents of the parks area regard hogs as natures bounty, a valued
resource to be used and perhaps managed and protected by people. Similar variation in
attitudes towards an introduced plant species is found in a study by Hall (2009).
In both the St. Johns and Big Bend cases, people who had for generations
inhabited the island had ideas of what species were natural for their ecosystem, based
on their experience and collective memory, that were radically different from government
ecologists and resource managers who based their assessments on notions of
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biogeography and the geologic record. A whole societys overall interactions with and
attitudes toward introduced species can also change over time, sometimes oscillating
several times between mostly favorable and mostly unfavorable as the species
introduction unfolds (Coates 2007).
As Pfeiffer and Voelks, (2009) show in their exhaustive review of human
interactions with introduced species, local peoples experiences with introduced species
are widely varied, ranging from disasters resulting in ecosystem disturbance, loss of
biodiversity and loss of livelihoods (e.g. Nile Perch in Lake Victoria; Goldsmidcht 1999)
to relatively small ecological impacts coupled with new economic opportunities (e.g. Hall
2009). In some cases, even reviled introduced species such as the zebra mussel have even
improved environmental quality in eutrophic lakes, benefiting endemic fish populations
(Reed-Andersen et al. 2000; Reeders and Bij de Vaate 1990).
Pfeiffer and Voeks (2009) developed a useful typology of introduced species
based on their interactions with humans and their cultural systems. They defined
culturally invasive biota as non-native organisms or genetic material that have
ecologically displaced or extirpated native biota, resulting in a detectable cultural impact
on resident societies (page 2). They further categorized introduced species, based on
their interactions with resident human groups as either culturally impoverishing,
culturally enriching, or culturally facilitating (page 2).
Even conservation-minded ecological scientists vary in their attitudes, and values
towards introduced species. While some view species introductions in general as a great
threat to the integrity of ecosystems worldwide, others advocate regarding species
introductions and their effects on ecosystems on a case-by-case basis. In a debate in the
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journal Conservation Biology between 1990 and 1992, three influential ecological
scientists (Stanley Temple, Ariel Lugo and Bruce Coblenz) presented opposing views of
the role people and policy should play in confronting introduced (called exotic in the
debate) species. In an editorial titled: Eradicating Exotics: A Nasty Necessity, Temple
(1990) argued that a deal of human resources and effort should be directed to eradicating
exotic species from places where they might be creating problems for native species.
Ariel Lugo responded a in a letter to the editor a few months later (Lugo 1990), stating
that removal of established exotic species is often a complex undertaking of uncertain
results and dubious chances of success, that no species should be seen as inherently evil
or harmful just because it wasnt native to that location, and that an assessment of
harmfulness or beneficence should be done empirically (Lugo 1990). Bruce Coblenz
weighed in to align himself mostly with Temples position. The journal-based debate got
quite heated: Lugo was accused of having a cornucopian view of nature, a statement he
apparently took offense to in a later response (Lugo 1992).
One of the striking features of the short public debate scribed above is that while
the authors presented quite opposing views about introduced species, they were all
concerned with and defending healthy ecosystem functions and biodiversity and they
based their opinions on what each deemed was good scientific evidence. What they
differed about was their appreciation of which species should be allowed to be part of a
given ecological community, i.e. what makes a species a suitable member of the
community.
The focal point of these and similar debates (e.f. Sagoff 2003; Simberloff 2003;
Subramanian 2008) and disagreements is the different actors appreciation of what
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constitutes a valid ecological community. Benedict Anderson used the term imagined
communities to describe the historically-recent rise of nationalism as a powerful
political and ideological force in worldwide politics (Anderson 1983). For Anderson, the
modern nation is an example of an imagined political community because people of the
same nationality conceive themselves as a bounded community distinct from others and
united by a measure of comradeship, even though they will never have any kind of
interaction with the vast majority of fellow nationals and despite the fact many of these
nationals are their competitors or even their oppressors.
The imagined communities concept has important implications for this analysis.
By accepting that the boundaries that define a community are, to an extent, imagined, the
possibility opens up that people might have competing ideas of what the communitys
membership is or should be, where the boundary between a community and the next one
should lie, and what type of boundary it should be. What people call ecosystems are by
and large really open, dynamic entities. However, the mere use of the word system
implies a border of some fashion inside of which lie the components of the system and
outside of which are non-system entities. Categorization, classification, and the drawing
of boundaries are essential to understanding the world by reducing the vast complexity of
the world to manageable amounts of information. Where and how such boundaries (for
example between the natural and non-natural distributions of an organism) are
drawn, however, is a decision made by people based on criteria, preferences, needs, and
values that are often culturally shared and mediated.
Whether or not a novel species is accepted by people, and specially by local
ecological scientists, as a natural or naturalized component of the system, is not a
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trivial issue: if a species believed to be introduced or exotic also is also put in the
category of potentially harmful, or invasive, it can lead to expensive, laborious, and
even ecologically destructive (Bergstrom et al. 2009; Cadotte 2009) eradication
initiatives. Conversely, any species that becomes established in a novel ecosystem will
initiate some changes, and people will be better able to take effective action if they have
an accurate idea of the interactions happening as a result of the novel species activities.
We are of the opinion that species introductions and their life histories are
complex phenomena, influenced by both socio-cultural and ecological factors.
Interdisciplinarily-conceived studies and analyses (not mere combinations of methods)
are necessary to truly understand species introductions and to inform environmental
policy. In the rest of this article we will present some findings of our research about
people-green iguana interactions in the San Juan Bay Estuary in Puerto Rico, as well as
some of the implications for policy regarding this and other similar species introductions.
Brief history of the green iguana introduction
Biology and Natural History of the Green Iguana
Iguana iguana is a large and widely distributed arboreal lizard from the Neotropics,
ranging in distribution from Mxico and the Caribbean, to northern Argentina in South
America (Schwartz & Henderson 1991). It is sexually dimorphic, with the males being
larger and more ornamented than females (Rivero 1998). Mature males can reach a
length of two meters and a weight of over 15 pounds. Iguanas reach sexual maturity at
about 16 months and large females can lay over 60 eggs. The nest site needs to remain at
30 C, and is often located in exposed sandy or loamy substrate (Rivero 1998). The green
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iguana is considered a social reptile species with individuals gathering in locations for
feeding, reproduction, and thermoregulation (Phillips et al. 1993).
Green iguanas are distinguished form other lizards in that they are uniquely adapted
to herbivorous and arboreal life (Hirth 1963, Troyer 1984, Britton 2002). Green iguanas
possesses small, evenly sized, sharp teeth that are unique among reptiles because they are
specially shaped to easily cut leaves (Montanucci 1968, King 1996). They have extra
long toes that allow them to easily climb and walk trough tree canopies and branches.
They digest tough cellulose and other plant material by hind-gut fermentation even at the
juvenile stages of their life (Troyer 1984, 1984a, King 1996, Britton 2002). Although
most substantiated accounts of green iguana diets in the wild show that green iguanas are
fully or almost fully herbivorous, the composition of the green iguanas diet, specifically
whether they are just herbivores or omnivores that represent a predatory danger to Puerto
Rican island fauna, is a controversial topic for the popular press and conservation sectors
in the island (e.g. Cedeo 2009).
Green iguanas have long been a food resource for people throughout their original
range in Central and South America. For thousands of years, iguanas have been hunted as
well as kept and raised by people for their meat (Benson 1977; Coe and Flannery 1967).
In Puerto Rico its been widely known for years that people in Central and South
America eat green iguanas and that gallina de palo (tree chicken), one of the names by
which the green iguana is known in Central America, refers both to the iguana meats
chicken-like quality and its importance as a staple food item.
Green iguanas are also popular pets and figure importantly in the modern live
reptile trade. They are easily tamed and breed well in captivity. The Smithsonian
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National Zoo reports that 800K green iguanas were imported into the United States in
1995 alone. Numerous websites are dedicated to green iguana pet keeping, care, and
reproduction. The modern pet-shop based trade in green iguanas in the US dates at least
back to the 1960s, but there was a great surge in pet trade popularity for iguanas and
other prehistoric-looking reptiles in the mid-late 1990s that has been attributed to an
increase in peoples interest in such reptiles after the release of the Hollywood
blockbuster movie Jurassic Park (Christy 2008).
Iguanas began to be regularly spotted in the estuaries near San Juan, Puerto Ricos
capital and most populous county in the between the 1980s and 1990s, and by the early
2000s several government agencies and news media channels began to regularly address
the increasing green iguana populations in Puerto Rico. Several of our informants
reported that wild green iguanas have been established in parts of eastern Puerto Rico for
several decades. Interestingly, while it seems clear that the trade in pet green iguanas is
largely responsible for the recent explosion in green iguana populations in Puerto Rico,
there is still speculation, based on some historical and genetic evidence, that waves of
green iguanas might have been reaching the Virgin Islands and possibly Puerto Rico over
the years by a combination of rafting and introduction by humans (Stahl 2009).
In 2007 Jorge Bauz, the science coordinator of the San Juan Bay Estuary
Consortium (SJBE) and authors Carlo-Joglar and Garca-Quijano designed a program for
the interdisciplinary monitoring of green iguanas and their interactions with human and
non-human components of the estuarys ecosystem. The SJBE is a consortium of federal
agencies, Puerto Rican state agencies, and NGOs with the common objective of
coordinating research, education, and resource management in the largest mangrove
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estuary in Puerto Rico. The goal of the sociocultural component of this research was to
explore Puerto Ricans attitudes, values, and knowledge about introduced species with
emphasis on the green iguana, to provide a description of the interactions between people
and green iguanas in the SBJE, and to develop a framework to collaborate with SBJE
residents and resource users in monitoring of introduced iguana populations.
In the rest of this article, we will describe some remarkable findings of our
research about the interactions between green iguanas and people in the SJBE. Because
we used varied methods and approaches for different research questions, the relevant
methods will be detailed in each section. The results of the wildlife ecology component
of our research can be found in our technical report to the SJBE (Carlo-Joglar and
Garca-Quijano 2008) and are being prepared for submission to appropriate thematic
journals.
A. The spatial association between human activities and green iguana populations
One of our principal fieldwork activities consisted in mapping the distribution of
green iguana populations in the SBJE region to assess the spatial abundance patterns of
iguanas in the estuary. We wanted to assess approximately how many iguanas were living
in the SBJE, in which parts of the estuary they were concentrated (and thus more likely to
cause an impact), what resources were the iguanas utilizing, and what features of the
ecosystem would be good predictors of iguana concentrations.
We conducted a landscape-scale adult iguana census in the mangroves of the
SJBE from May through August of 2008. Navigation with a small boat and kayaks was
used to count iguanas at edges of lagoons. Transects on foot were established to count
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iguanas inside mangrove forests far from edges (at least 100 m from the nearest edge),
and on non-mangrove secondary growth vegetation bordering mangrove forest.
Observers worked in pairs, with one person watching, and the other recording the data.
Once an iguana was detected, we recorded the spatial coordinates of iguana location with
a handheld GPS For each location, we recorded the # of iguanas per tree, tree species,
and a category of the degree of defoliation of the tree, if any was observable. All
defoliated trees were mapped regardless of the presence of iguanas since they may
represent unseen animals or previous iguana aggregations.
We performed an Ordinal Logistic Regression Analysis of iguana detections
(presence or absence) as a function of distance to the 1) nearest vegetation edge (i.e., non-
mangrove vegetation such as pasture, scrubland, secondary forest, etc.), and 2) the distance to
the nearest human settlement (house, buildings, etc.). This procedure consisted of randomly
generating sampling points over the iguana distribution map, using the random points to
locate the nearest sampling transect location, and from there measuring distance to edges and
urban structures, and whether iguanas were detected in the vicinity.
Iguanas were not distributed randomly across the SJBE (figure 1). We found that
both the distance to nearest vegetation edge (r2=0.25, p
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Iguanas were significantly aggregated towards the borders of the mangrove forests
We found a total of 1625 adult iguanas (Table 1), of which 97.6% were found on
trees at the edges of lagoons, channels, and bays. On the other hand, the number of iguanas in
mangrove forest away from edges was 0.20%. Non-mangrove forests were not well
represented because they were rare and only a proportionally small region was sampled in
Piones for about 1 % of the iguanas. Two of the largest mangrove lagoons in the SJBE,
Torrecilla and Cao Martn Pea lagoons (see figure 2), contained 85 % of all iguana records
but represented only 42 % of the linear distance of the surveys. Iguanas were virtually absent
away from edges and were rare in pure mangrove patches in these lagoons and elsewhere,
with only 3 iguanas detected in within-mangrove transects.
This finding has important implications regarding peoples perceptions of the
severity and impacts of the green iguana populations in the SJBE. First, the vast majority
of people who visit or pass by the SJBEs mangrove forests only observe the forest edge
areas of the estuary rather than the inner forest areas. This can create an illusion of
abundance because the part of the mangrove that people are observing is precisely where
green iguanas are disproportionately concentrated. Were casual observers to penetrate the
forest just a few meters, they would find that green iguanas are far from abundant in the
vast majority of the mangrove forest. In other words, people that are just observing the
forest edges might form an erroneous mental image of a forest packed with green
iguanas.
The second implication is that green iguanas are probably having a less severe
impact on climax mangrove forests than what both laypeople and environmentalists
might have feared. A highly successful multi-sector educational campaign about the
value (intrinsic and practical) of mangrove forests for Puerto Ricans has educated many
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Puerto Ricans to view mangroves as treasured natural resources rather than sources of
pestilence and mosquito-borne diseases, especially malaria, as they were viewed during
much of the 20th
century. Thus, one of the principal sources of concern about the green
iguana introduction was related to the impacts that iguanas might have on mangrove
forests. Our findings suggest that iguanas can have significant impacts on localized
mangrove stands near forest edges, but by and large, the majority of mangrove forests are
not being impacted. In contrast with the less diverse inner forest, mangrove forest edge
areas usually contain not just mangrove trees, but a combination of mangroves with other
types of trees along with grasses, shrubs, and vines.
There was a spatial association between human settlements and iguana populations.
This is consistent with what is known about many species introductions: that
because of the profound effect that human activities can have on the landscape, one of the
most important characteristics that a potentially invasive species (introduced or native)
can have is its ability to adapt and thrive in proximity to humans and human-caused
changes. For example, one of the reasons why the English Sparrow was able to establish
large populations across the continental United States after its introduction in the East
Coast was that it was able to exploit two abundant and predictable resources: human
garbage and undigested seeds in carriage horse droppings (Coates 2007). Similarly,
coyotes have been able to spread farther beyond their prehistoric ranges in the United
States (and thus become domestically invasive) because of their ability to find food and
reproduce in areas of high human habitation. This underscores one of the main points of
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our research approach: that species introductions cannot be understood in isolation from
the human component (also see Cadotte 2009a).
Figure 1. Location of iguana sightings at the Condado Lagoon (top left), Torrecilla
Lagoon (top right), San Jos Lagoon(bottom left), and Cao Martn Pea (bottom right).
Figure 2. Ordinal Logistic Regression model estimating the probability of encountering agreen iguana as a function of distance to a non-mangrove vegetation edge (left panel) and
distance to a human settlement edge (right panel). Analyses were made using JMP 7.0(SAS Institute).
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B. Variation in cultural experiences, attitudes and values about green iguanas in
Puerto Rico
We conducted interviews with residents, recreational and subsistence resource users
of the estuary to assess the following crucial management-related questions:
- What do people think about introduced species, particularly about the greeniguana, in Puerto Rico?
- What do people know about the green iguana and how does their knowledgecompare with news/media accounts of iguana introductions and with ecologicalmonitoring results?
- What effect, if any, have green iguanas had in the use and enjoyment of the SJBEby residents and visitors?
Semi-Structured Interviews
We conducted 15 ethnographic, semi-structured interviews with SBJE residents
and 25 structured intercept interviews with SBJE recreational and subsistence resource
users.
The semi-structured interviews with residents and people with continued
experience on the estuary consisted of extended conversations about green iguanas and
exotic species in the SJBE and, using an interview guide or protocol that included basic
demographic data and questions about the respondents experiences with green iguanas in
the estuary. Answers were recorded by taking field notes during and immediately after
the interviews. Field notes were entered into word processing software and analyzed for
content and recurrence of topics and themes using Atlas.ti (Muhr 2004) qualitative
analysis software.
Respondents to the semi-structured interviews included SBJE residents (10),
Gardeners/groundskeepers (3) and crabbers/fishermen (2). Nine were male and 6 were
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female. All respondents reported continued experiences with iguanas in the estuary and
expressed interest in collaborating with SJBE officials and researchers to learn and
exchange information about the green iguana. They reported that there have been iguanas
in the SJBE for at least 20-30 years, especially towards the eastern portions of the
estuary. All reported that at present they know that iguanas were introduced to Puerto
Rico by pet shops and the pet trade before they escaped and became established in the
wild. However, six informants reported not realizing that the iguanas were introduced or
non-native until recently (about the last 5 years), with the increased coverage of iguana
introductions in the news media.
Seven of the interviewed residents had an overall positive attitude towards
iguanas, saying that they were an interesting part of the landscape that they and/or their
families enjoyed watching and interacting with. Six informants reported mixed feelings,
citing that while they sometimes enjoyed watching iguanas, they were sometimes
inconvenienced by iguanas near their homes or that they were worried about the iguanas
effects on the ecosystem. The three main sources of iguana-caused inconveniences cited
by respondents were related to iguanas feeding on or otherwise damaging residential
gardens, iguana-car collisions or near-collisions in roadways, and iguanas causing fear or
disgust to residents due to the iguanas physical appearance. Two informants expressed
that they did not welcome the iguanas in the SBJE landscape (or in Puerto Rico, for that
matter) at all.
All informants showed interest in learning more about the iguanas. Specifically,
12 of them wanted to know more about studies of what the iguanas are doing and how
they affect the environment locally, in the SJBE and in Puerto Rico. For example, several
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informants (10) expressed confusion about media accounts of the iguana as a predator of
native bird eggs and amphibians because their own personal observations indicated that
iguanas were vegetarian creatures. They also expressed that they would like to see a
serious study about iguana diets. Due to their interest in knowing more about the green
iguana, the informants reported that they actively seek information about iguanas, iguana
behavior, effects of iguanas in the ecosystem and their potential to harm people and pets.
Their main sources of information about iguanas were personal observation,
conversations with friends, neighbors, and acquaintances, library books, and the internet.
Most of the interviewed SBJE residents (12) found the idea of systematically
killing green iguanas as a control strategy objectionable, citing the iguanas right to live,
the fundamental tenet of respect for life, and that they are also creatures of God.
Also, several informants mentioned that they would feel bad if iguanas were
systematically slaughtered because the iguanas did not ask to be here. The following
excerpt from a June 2008 interview with a 64 year old security guard illustrates this:
R: I feel very sorry when I see an iguana esparrach (as road kill) en la carretera.They are beautiful little animals!
CGG: What do you think about killing iguanas as an introduced species controlstrategy?
R: I dont like it. I do not understand why (people would do this). The iguanas didnot ask to be here, to be brought here to Puerto Rico. Whoever kills a little animaljust like that, forgets that up there, there is a God watching us.
However, several informants considered two exceptions where it would be
acceptable to kill iguanas: 1) When their presence becomes a grave physical hazard for
humans (e.g. when basking iguanas interfere with airport safety in airport runways), and
2) if the iguanas are being slaughtered as a food resource. A quote from male informant
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who is a municipal employee and a part-time small-scale farmer illustrates this: Many
people, in Puerto Rico, are poor, they do not have money to go to the supermarket and
buy good quality meat. Many of you in San Juan dont see it, but there is hunger in
Puerto Rico. The iguana is a good food resource, and people should use it( interview,
May 2008). However, this same informant mentioned that he would not like to see a for-
profit industry of iguana meat products in Puerto Rico. He was especially opposed to the
idea of iguana meat becoming a luxury food item. This is because, in his words, iguana
meat would become an expensive foodstuff, which would exclude people who do not
have the money, just like it happens nowadays with meat in the supermarkets.
Structured intercept interviews with SBJE recreational and subsistence resource
users
A short, structured questionnaire was administered to 25 recreational resource
users of the SJBE. Questionnaire respondents were intercepted while the respondents
were visiting the estuary recreational facilities in the Parque Central and Piones of the
SJBE (see figure 1) areas on haphazardly chosen dates (usually the same day field iguana
census observations were carried out). The structured questionnaire was designed and
pre-tested for a 15-20 minute interview, and consisted of short, focused questions about:
1) respondents intended activities in the SJBE, 2) attitudes and knowledge about
introduced species in general and about the green iguana in Puerto Rico and the SJBE, 3)
their experience with iguanas in the SJBE, and 4) the effects that green iguanas have in
their use and enjoyment of the estuary. Besides this information, we also collected basic
demographic data to test whether factors such as education, gender, or place of residence
had an effect on the responses. Answers to questionnaire items were recorded by the PI
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and research assistants in the field by filling out a structured interview instrument and
later coded for analysis.
The respondents to the structured questionnaire were residents of 9 municipalities
of Puerto Rico (San Juan, Dorado, Trujillo Alto, Caguas, Carolina, Loza, Bayamn,
Caguas, and Toa Baja). 22 were visiting the SJBE for exercise/leisure activities and 3
were engaging in subsistence/recreational fishing and land crab hunting. Their ages
ranged from 18 to 60 years old (average 38 years old). Their self-reported highest
completed education levels included: High School (8), College (13), and Graduate
Degrees (4). Thirteen respondents were female and 12 were males.
Attitudes towards exotic species and the green iguana
Several intercept interview respondents (16) expressed confusion about what the
terms exotic species or introduced species meant. It was often necessary to further
explain the concept to respondents (e.g. species introduced by people to localities where
they did not occur otherwise and which became established in the wild).
Questionnaire items asking peoples opinions of exotic species and about green
iguanas in Puerto Rico were coded by whether they represented: 1) positive, 2) negative,
or 3) neutral/ambiguous opinions and/or attitudes about these matters. There was ample
variation in the respondents general opinions about exotic species in PR (6 positive, 8
negative, 11 neutral/ambiguous). Opinions about the green iguana in Puerto Rico were
slightly more positive (12 positive, 7 negative, 6 neutral/ambiguous).
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We tested whether there were relationship between demographic characteristics of
the respondents such as (highest education level completed, gender, age) and their
attitudes towards exotic species and iguanas. We found no significant relationships in the
comparison, except for a weak relationship between highest education completed and
attitudes towards exotic species in general (X2= 8.736; p=.068), that indicates that people
with higher education levels tended to have more formed opinions towards exotic
species, and thus less neutral/ambiguous responses, than people with lower completed
education levels (there were almost equal numbers of positive vs. negative responses).
This might suggest that those with college-level education have been introduced more
often to scientific and news media about the global concern for species introductions.
However, since we identified ourselves as university researchers, this response pattern
might also just mean that college educated respondents were more confident in telling us
their opinions than non college-educated respondents. A larger sample with more
respondents would probably be needed to differentiate between these two possibilities.
Table 1. Relationships between some demographic parameters and intercept
questionnaire respondents attitudes towards exotic species and the green iguana in
Puerto Rico
Attitude towards Exotic Species Attitude towards Green Iguanas
Chi sq. p Chi sq. pAge 1.11 0.57 2.3 0.32
Gender 0.05 0.97 1.12 0.57
Ed. Level 8.74 0.07 3.44 0.49
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The textual responses provided by the respondents to the questionnaire reveal
perhaps more tellingly the variation in peoples opinions about iguanas. Answers to the
questions about the presence of iguanas in Puerto Ricos estuaries ranged from I love
them (the iguanas). I enjoy watching them immensely (September interview with 30 year
old female), and They do not bother me. The iguanas do not affect me one way or the
other (August 2008 interview with 35 year-old male) to I hate those animals, they are
ugly and we should kill them all (July 2008 interview with 59 year old male).
C. What do green iguanas eat? Local and scientific knowledge in the controversy
about the green iguana introduction
The diet of the iguana, specifically whether green iguanas routinely eat animals
such as birds, small eggs, lizards (Anolis sp.), coqu tree frogs (Eleutherodactylus sp.),
and insects, is at the heart of the controversy in media and scientific circles regarding the
introduction of the green iguana and the possible impact of the green iguana in Puerto
Rico. Although the vast majority of the scientific literature indicates that green iguanas
are herbivores, news media coverage of iguana introductions tends to emphasize the
largely unsubstantiated accounts that iguanas in the wild will pursue and eat small native
fauna (e.g. Cedeo and Cordero 2009).
Along with our teams field observations of iguana feeding behavior and diets, we
wanted to know what SJBE residents and resource users think green iguanas eat. We
asked 28 of SJBE residents and resource users to freelist all the items that to their
knowledge are eaten by iguanas. The freelisting elicitation technique is used to elicit the
items comprising a cultural domain (Bernard 2002; DAndrade 1995). We used
ANTHROPAC X (Borgatti 2001) to analyze the freelists for frequency of appearance in
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lists, average rank, and Smiths S salience (a composite parameter from frequency and
average rank of an item across all the lists in the sample) (Borgatti 1996). Smiths S was
used as the principal criterion for ranking iguana diet items listed by the 28 respondents
to the freelist exercise.
Table 2 shows the total number of items mentioned by respondents as being part
of green iguana diets, along with frequencies and Smiths salience values. A relatively
small number repeated items form the bulk of the responses, a j-curved pattern of
consensus within diversity (Barrett 1995) that indicates that there is consensus among
respondents about core domain items (figure 3). The most salient and frequently
mentioned core iguana diet domain items mentioned by SJBE residents and resource
users were all plant materials, with the first 10 items in terms of salience and the first 11
in terms of frequency being plants. Of the total 76 cumulative items mentioned in all the
lists of iguana diets, 62 were plant material, 9 were animal material, and 5 were non-
specific in terms of plant/animal material (e.g. leftovers, whatever it finds, etc.).
The residents responses are more similar to our systematic field monitoring and
experiment results than the supposedly science-informed media. Our ecological
monitoring activities, which have included focal observations of iguanas, bird nest
predation experiments, and iguana stomach content analysis, indicate that green iguanas
in the SJBE are feeding as strict herbivores (Carlo and Garca-Quijano 2009). Together
with qualitative interview data, these results suggest that the respondents pay more
attention to their own observations of, knowledge about, and experience with green
iguanas than to media accounts that tend to emphasize fears about the iguanas as
predators of native fauna. This underscores residents and resource users potential as
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possible collaborators to managers in monitoring iguanas and other introduced species
activities in the ecosystem (also see Bart 2009).
Table 2. Items mentioned by SJBE residents and resource users in freelisting
exercises about items eaten by the green iguana.
Freelist Item Smith's S FREQUENCY
Leaves 0.268 9
Plants 0.182 7
Vegetation 0.179 5
Lettuce 0.158 6
Hibiscus flowers 0.095 3
Fruit 0.092 5
Grass 0.076 4
Flowers 0.057 2
Vegetables 0.054 2
Food scraps 0.051 4
Meat 0.049 2
Insects 0.042 2
Bread 0.036 1
Mosquitoes 0.036 1
Whatever it finds 0.036 1
Mangroves 0.036 1
Citrics 0.036 1
Trees 0.036 1
Bananas 0.036
1
Anolis Lizards 0.031 1
Moca tree 0.031 1
Red Currant 0.027 1
Guavas 0.025 2
Peanut flower 0.024 1
Cabbage 0.022 1
Mangos 0.018 1
Sweet potatoes 0.018 1
Bread 0.018 1
Carrots 0.018 1
Eggs 0.018 1Apples 0.013 1
Carrion 0.012 1
Pears 0.009 1
Skink lizards 0.009 1
Oranges 0.009 1
Hcar trees 0.004 1
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Figure 3. Graph showing salience (Smiths S) of items mentioned in iguana food
freelist exercises.
0
0.05
0.1
0.15
0.2
0.25
0.3
HOJAS
PLANT
AS
VE
GET
ACION
LECHUGA
AMAPOLAS
FRUTAS
HIERBA
FLORES
V
EGETAL
ES
SOBRAS
CAR
NE
INSECTOS
PAN
M
OSQUITOS
LOQUEE
NCUENTRA
MANGL
ES
CITRICOS
ARBOL
ES
GUINEO
LA
GARTIJOS
MOCA
ACERO
LA
GUAYABA
FLOR
DEMANI
REP
OLLO
MAN
GO
MAL
ANGA
GALLETAS
Z
ANAH
ORIA
HUEVOS
MANZA
NA
ANIM
ALES
MUERTOS
PERA
CIGUANAS
NARAN
JA
HUCAR
Mentioned iguana diet items
Smith's S
D. Interactions between green iguanas and Puerto Ricos tourism industry
A repeated theme in our ethnographic interviews about the green iguana in Puerto
Rico was that green iguanas were becoming animals of interest for foreign and local
tourists visiting coastal, estuarine and riverside areas in San Juan and eastern Puerto Rico.
This supported our own observations of tourism industrys use of iguanas (large,
interesting, and prehistoric-looking land animals which are easily observable and can be
tamed) as an attraction and entertainment for tourists.
Probably the most well-known use of iguanas as entertainment for tourism in
Puerto Rico is the iguana-feeding stations and iguana watching/iguana crossing signs
that have been posted for more than 5 years by the Westin Riomar Resort in Ro Grande,
Puerto Rico (Figure 2). Our ethnographic informants also mentioned the proliferation of
iguana-watching kayak and boat tours in the SJBE, as well as other coastal Puerto Rican
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locations, caged iguanas kept in the lobbies and pool areas of luxury hotels in (the same
way that other exotic-looking animals such as flamingos, parrots, peacocks, monkeys,
and toucans have kept in Puerto Rico hotel common areas for decades), as well as
repeated instances of both Puerto Rican and foreign tourists asking SJBE residents for
good iguana-watching spots. In virtually all of our field visits to the Parque Lineal area of
the SBJE we observed people (individuals, couples, and family groups) engaged in
watching iguanas and sharing observations about the iguanas.
Tourism is an important and growing source of revenue in coastal areas of
tropical islands, including Puerto Rico. One of the ways tourism generates revenue for
receiving locales is the selling ofsouvenirs, objects such as photographs, postcards,
clothing, figurines, and others, that serve as a remembrance of a salient or interesting
feature of the visited country or locales. The main purpose of buying a souvenir is to
acquire an object which can later serve as a symbol or a memory-generating object of the
visited locale, for either the visitor or a person back home who receives the item as a gift
(Goldman 2004)). Because of this, we hypothesized that if in fact green iguanas were
becoming important for Puerto Ricos tourism industry, we should see significant
presence of iguanas assouvenirs in tourist gift-shops.
To test this hypothesis, we conducted a systematic cultural mapping exercise in
tourist gift-shops located in the tourism center of Old San Juan, Puerto Rico. The cultural
mapping exercise consisted of visiting all the tourist gift shops in Old San Juan and
systematically looking at the items on sale to look for green-iguana based or inspired
objects. We also interviewed gift shop clerks and/or owners to ask them about tourist
demand for iguana-theme items and, if iguana-themed items were found, why they had
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made the decision to include these objects in their inventories. We also wanted to know
whether tourists would ever visit stores asking specifically for iguana memorabilia.
If an iguana-themed item on sale was found, we recorded the name and location
of the store, a description of the item, the selling price, the place of manufacture or
fabrication of the item, whether the item specifically referred to the green iguana, to
iguanas in Puerto Rico, and if the iguana figure or item had the iguanas appearing
together with the words Puerto Rico or with one or more established symbols of Puerto
Rico such as coqu tree frogs (Eleutherodactylus sp.), the Puerto Rican parrot (Amazona
vittata), the Puerto Rican flag, iconic musical cultural symbols such as the cuatro
guitar, and others.
The sampling universe consisted of 54 stores of varying sizes located through the
OSJ area but mostly concentrated in the Fortaleza and San Francisco Streets). We found
78 iguana-themedsouveniritems in 33 of the 54 tourist gift shops. The items ranged from
cheap, mass-produced items such as postcards and trinkets (e.g. magnets, shot glasses,
plastic toys) selling for a few dollars to luxury items like hand-carved precious wood
statues prices selling for several hundred dollars. However, souvenir gift shop trade is
mostly a small-priced commodity trade; thus the median price of all the iguana-themed
items detected was $12.50. The iguana-themed items ranged from locally-made artisanal
items to mass-produced commodities made in places like Indonesia, Mexico, China,
Ecuador, and the USA.
The kinds of iguana-themed items we found in this cultural mapping exercise
included t-shirts, carvings, refrigerator magnets, dolls, figurines, rubber toys, shot
glasses, water-filled glass balls, puppets, post cards, beach towels, incense holders, flutes,
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small tambourines, and others. Seventy-four of the items referred specifically to Iguana
iguana and 57 of those referred specifically to green iguanas in Puerto Rico. Fifty-four
items had green iguanas together with the words Puerto Rico. Finally, 19 items had
iguanas appearing together with other cultural symbols of Puerto Rico, such as cuatro
guitars, coqu frogs, vejigante carnival masks, and the Puerto Rican parrot. A second
round of cultural mapping exercise is currently underway, to verify whether iguana-
themedsouveniritems are increasing over time or not, to perform additional observations
to estimate the proportion of iguana-themed items to other iconic Puerto Rican fauna.
The short informal interviews with gift shop store clerks and owners revealed that
foreign tourists routinely go into gift shops asking specifically for iguana-themed
souvenirs. Moreover, the gift shop store owners told us that they had increased the
number of iguana-themed items in their inventories mostly as a response to consumer
demand. That is, that the tourists own experiences and observations of green iguanas had
compelled them to look for iguana souvenirs when they visited gift shops. A gift shop
clerk described this process: tourists see the iguanas in hotel lobbies or in the wild, or
the tour guides take them to see the iguanas. The tourists find them impressive and then
they come here and ask, specifically, about iguana things (07/14/08 interview). This
may indicate that iguanas are a salient component of at least some foreign tourists
experiences in the island. As one of the gift shop owners put it, (the iguanas) are part of
the island, they are part of what you see in the island. And they are something impressive.
For the tourist, the iguana is like a coqu (frog) (07/14/08 interview).
If we had any doubts about whether our souvenir shop cultural mapping exercise
was more than just a trivial observations, these doubts quickly dissapeared when the
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initial technical report that included results of our tourism cultural mapping exercise were
made available to the Puerto Rican media through the SJBE research office. At least 4
articles quickly appeared in El Nuevo Dia and Primera Hora, two of the three
principal Puerto Rican newspaper, with headlines such as La Iguana Verde Amenaza
Permanencia Del Coqu Como Imagen Turstica (The Green Iguana Threatens the
Importance of the Coqu as A Tourism Symbol) (Justicia Doll 2009; Cordero 2009).
Clearly, many Puerto Ricans hold in high regard the coqu frog as an international
symbol for Puerto Rico. Worries about green iguanas displacing coqufrogs in souvenir
shops are probably unwarranted, since more than 500 different coqu-themed souvenirs
were counted in our exercise, compared with 74 iguana-themed ones. However, the
reaction to the presence of the iguana in the tourist souvenir trade shows how even
symbolic interactions between native and exotic fauna (real coqufrogs are not affected
one way or another by iguana items in tourist shops) can be a significant cultural impact
for people in the host geographic location.
Figure 2. Iguana crossing and Iguana feeding station signs in the Westin
Riomar Resort in Ro Grande, Puerto Rico.
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Figure 4. Examples of iguana-themed tourist memorabilia sold in Old San Juan
tourist gift shop stores.
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Conclusion
Anthropogenic species introductions are, by definition, a human phenomena. As
such, they are driven by cultural, social, and technological factors as much as they are
driven by biological ones. However, with some important exceptions, social sciences and
specifically applied anthropology have been largely left out of the study of species
introductions. Despite worldwide alarm, the rate of species introductions seem to be only
accelerating and achieving a comprehensive, interdisciplinary understanding of the
phenomena is becoming only more urgent.
The results presented in this article were used for developing several
recommendations regarding the management of green iguanas in the SJBE. These
recommendations are detailed in the insert below.
Management Recommendations resulting from sociocultural component
of green iguana monitoring activities:
1. Further exploring the potential of people in the SJBE as plausible collaboratorsin the monitoring of green iguanas activities.
2. For as long as there are iguanas in the estuary, to take advantage of the greeniguanas positive interactions with the tourism industry and charisma as aninteresting species to organize activities that might channel revenue to SBJE
mostly impoverished residents; as well as to promote peoples interest in theestuarine ecosystems of SJBE and their protection from urban development.3. Because of the high spatial clumping of iguanas and their association with
In our opinion, the most potentially fruitful approach to their study of species
introductions and their impacts on host ecosystems (human and non-human alike) is to
recognize that species introductions are complex -and in many cases unavoidable-
phenomena, with varied interactions and outcomes. In an insightful conclusion to the
2008 review article on the cultural aspects of species introductions, Pfeiffer and Voeks
stated that recognition of the biocultural dimensions of invasive biota can contribute to
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a more balanced invasive species debate, whereby the function and meaning of invasive
plants and animals to (diverse human) communities is no longer absent from research,
management, or policy considerations. We align ourselves with Pfeiffer and Voeks
argument, perhaps adding that incorporating social and cultural dimensions of species
introductions will yield the best results within interdisciplinarily-conceived studies that
merge ecological and social sciences.
The results of our work with SJBE residents, resource users, an the San Juan
tourism industry resonate with previous findings elsewhere that people have varied
interactions, some positive, some negative and some neutral, with native and exotics
components of their ecosystem alike. Together with our findings about the spatial
association of introduced species and human activities, they also underscore that human-
dominated ecosystems and interactions within them are best understood when people are
conceptualized as part of the ecosystem and not some external factor to be addressed in
the policy and enforcement arenas only.
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