Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Ctenosaura similis
(black spiny-tailed iguana)



Ctenosaura similis (black spiny-tailed iguana)


  • Last modified
  • 06 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Natural Enemy
  • Host Animal
  • Preferred Scientific Name
  • Ctenosaura similis
  • Preferred Common Name
  • black spiny-tailed iguana
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Chordata
  •       Subphylum: Vertebrata
  •         Class: Reptilia
  • Summary of Invasiveness
  • Ctenosaura similis, commonly known as black spiny-tailed iguana, is the largest and most widely distributed ctenosaur. Its native range stretches from southern Mexico to Panama where is exploited for food and t...

Don't need the entire report?

Generate a print friendly version containing only the sections you need.

Generate report


Top of page
Ctenosaura similis (black spiny-tailed iguana); male (centre) with two females. Barra Honda national park, Costa Rica. February 2007.
CaptionCtenosaura similis (black spiny-tailed iguana); male (centre) with two females. Barra Honda national park, Costa Rica. February 2007.
Copyright©Christian Mehlführer-2007, Vienna, Austria/via wikipedia - CC BY 2.5
Ctenosaura similis (black spiny-tailed iguana); male (centre) with two females. Barra Honda national park, Costa Rica. February 2007.
AdultsCtenosaura similis (black spiny-tailed iguana); male (centre) with two females. Barra Honda national park, Costa Rica. February 2007.©Christian Mehlführer-2007, Vienna, Austria/via wikipedia - CC BY 2.5
Ctenosaura similis (black spiny-tailed iguana); female. Barra Honda national park, Costa Rica. February 2007.
CaptionCtenosaura similis (black spiny-tailed iguana); female. Barra Honda national park, Costa Rica. February 2007.
Copyright©Christian Mehlführer-2007, Vienna, Austria/via wikipedia - CC BY 2.5
Ctenosaura similis (black spiny-tailed iguana); female. Barra Honda national park, Costa Rica. February 2007.
FemaleCtenosaura similis (black spiny-tailed iguana); female. Barra Honda national park, Costa Rica. February 2007.©Christian Mehlführer-2007, Vienna, Austria/via wikipedia - CC BY 2.5
Ctenosaura similis (black spiny-tailed iguana); male. Caye Caulker, Belize. March 2016.
CaptionCtenosaura similis (black spiny-tailed iguana); male. Caye Caulker, Belize. March 2016.
Copyright©Simon Pierre Barrette-2016/via wikipedia - CC BY-SA 4.0
Ctenosaura similis (black spiny-tailed iguana); male. Caye Caulker, Belize. March 2016.
MaleCtenosaura similis (black spiny-tailed iguana); male. Caye Caulker, Belize. March 2016.©Simon Pierre Barrette-2016/via wikipedia - CC BY-SA 4.0
Ctenosaura similis (black spiny-tailed iguana); close view of a male. Barra Honda national park, Costa Rica. February 2007.
CaptionCtenosaura similis (black spiny-tailed iguana); close view of a male. Barra Honda national park, Costa Rica. February 2007.
Copyright©Christian Mehlführer-2007, Vienna, Austria/via wikipedia - CC BY 2.5
Ctenosaura similis (black spiny-tailed iguana); close view of a male. Barra Honda national park, Costa Rica. February 2007.
MaleCtenosaura similis (black spiny-tailed iguana); close view of a male. Barra Honda national park, Costa Rica. February 2007.©Christian Mehlführer-2007, Vienna, Austria/via wikipedia - CC BY 2.5


Top of page

Preferred Scientific Name

  • Ctenosaura similis (Gray, 1831)

Preferred Common Name

  • black spiny-tailed iguana

International Common Names

  • English: black ctenosaur; black iguana; black spiny-tailed iguana; common spiny-tailed iguana; ctenosaur; Gray’s spiny-tailed iguana
  • Spanish: iguana-espinosa rayada

Local Common Names

  • Belize: wish willy
  • Colombia: ishilly
  • Costa Rica: garrobo; iguana negra
  • Germany: gemeiner schwarzleguan; schwarzer leguan
  • Nicaragua: garrobo negro

Summary of Invasiveness

Top of page

Ctenosaura similis, commonly known as black spiny-tailed iguana, is the largest and most widely distributed ctenosaur. Its native range stretches from southern Mexico to Panama where is exploited for food and traditional medicine. It generally is found in seasonally dry, lowland habitats but can occur in sites up to 900 m elevation. It is often found in close proximity to human activity. The capacity of C. similis to co-exist in altered environments coupled with its high fecundity has contributed to its successful establishment and spread in Florida, USA, where it consumes valuable horticultural plants, invades dwellings, and threatens imperilled native species through predation and usurpation of burrows. The invasive range of C. similis also includes Venezuela and the Colombian islands of Providencia and San Andres.

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Chordata
  •             Subphylum: Vertebrata
  •                 Class: Reptilia
  •                     Order: Sauria
  •                         Family: Iguanidae
  •                             Genus: Ctenosaura
  •                                 Species: Ctenosaura similis

Notes on Taxonomy and Nomenclature

Top of page

Based on morphological and genetic characteristics, Köhler et al. (2000) proposed grouping the 13 Ctenosaura species into 3 subgenera:

Subgenus Ctenosaura Wiegmann, 1828, status nov. - C. acanthura, C. hemilopha, C. pectinata and C. similis.

Subgenus Loganiosaura nov. - C. bakeri, C. melanosterna, C. oedirhina and C. palearis.

Subgenus Enyaliosaurus Gray, 1845 status nov. - C. alfredschmidti, C. clarki, C. defensor, C. flavidorsalis and C. quinquecarinata.

This scheme was subsequently considered untenable, and 18 species of Ctenosaura are now recognized (Iguana Taxonomy Working Group, 2011). According to the Iguana Taxonomy Working Group (2011), “A well-resolved phylogenetic hypothesis of all taxa in this genus is sorely needed.”

Hybridization between C. similis and C. bakeri has been documented on Utila Island in Honduras (Gutsche and Köhler, 2008; Pasachnik et al., 2009).


Top of page

Considered to be a “giant” iguanid lizard, with adult males approaching 500 mm snout-vent length (SVL) and females approaching 350 mm SVL in their native range (Fitch and Henderson, 1978).

Hatchlings are 43-60 mm SVL (Fitch and Henderson, 1978; Avery et al., 2014). In their native range, marked individuals grew at rates of 1.8-3.4 mm per week (SVL), and first-year males and females averaged 188 mm and 177 mm SVL, respectively (Fitch and Henderson, 1978).

C. similis eggs are elongated and soft-shelled, measuring about 27 x 18 mm. Fat reserves contribute directly to yolk deposition, follicle growth, and clutch size (Fitch and Henderson, 1978). In Florida, USA, the amount of abdominal fat in female ctenosaurs ranged from 0.5-114.5 g, or 0.3-13.4% of body mass (Avery et al., 2014).


Top of page

The native range of C. similis extends on the Atlantic versant from the Isthmus of Tehuantepec southward to northeastern Nicaragua, and on the Pacific versant from the Isthmus of Tehuantepec southward to Panama (Ko¨hler, 2003). It occurs in Mexico and throughout much of Central America (The Reptile Database, 2016).

This species was first introduced to Florida, USA, during the 1970s and has expanded its range from Gasparilla Island onto the adjacent mainland and islands and throughout the southwestern coast of Florida from Manatee County southward to Collier County. At the same time it was introduced on Key Biscayne in Miami (Butterfield et al., 1997; Krysko et al., 2009). C. similis is also found elsewhere on Florida’s southeastern coast in Martin and Broward counties (Krysko et al., 2011b), as well as in the Florida Keys on Big Pine Key and No Name Key, Monroe County (Enge et al., 2006; Krysko et al., 2011a; Anderson and Enge, 2012).

C. similis has been introduced to Colombia, Carribbean islands of (San Andres and Providencia islands) (Tamsitt and Valdivieso, 1963) and Venezuela (Barrio-Amorós and Rivas-Fuenmayor, 2008; Flores and Esqueda, 2008).

Distribution Table

Top of page

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

North America

MexicoPresentNativeKöhler, 2003; The Reptile Database, 2016Chiapas, Oaxaca, Yucatan, Quintana Roo
USAPresentPresent based on regional distribution.
-FloridaWidespreadIntroduced1979 Invasive Townsend et al., 2003a; Butterfield et al., 1997; Krysko et al., 2003; Krysko et al., 2010Gasparilla Island

Central America and Caribbean

BelizePresentNativeThe Reptile Database, 2016
Costa RicaPresentNativeThe Reptile Database, 2016
El SalvadorPresentNativeThe Reptile Database, 2016
GuatemalaPresentNativeThe Reptile Database, 2016
HondurasPresentNativeThe Reptile Database, 2016
NicaraguaPresentNativeKöhler, 2003; The Reptile Database, 2016
PanamaPresentNativeKöhler, 2003; The Reptile Database, 2016

South America

ColombiaLocalisedIntroducedbefore 1933 Invasive Tamsitt and Valdivieso, 1963San Andres and Providencia Islands, approximately 110 miles from mainland Central America
VenezuelaLocalisedIntroduced1998 Invasive Barrio-Amorós and Rivas-Fuenmayor, 2008; Flores and Esqueda, 2008Inhabiting gardens, parking lots and parks

History of Introduction and Spread

Top of page

Results of the genetic analysis by Nuñez (2016) are consistent with multiple introductions within Florida, USA. The Gasparilla Island population possibly originated from three animals kept as pets and then released around 1979 (Krysko et al., 2003). The population, which comprises a single haplotype, now extends from Sarasota south to Naples 180 km along Florida’s southwest coast. Ctenosaurs move freely off Gasparilla Island via causeways, are carried off the island incidentally by vehicles, and are taken purposely off the island by people. C. similis now occurs on Keeywadin Island, Little Marco Island, Cayo Costa, and probably other islands as a result of purposeful transport and releases by residents (Krysko et al., 2003).  In Collier County a private landowner released between 5-30 lizards on his property on the southern end of the Keewaydin Island in 1995 (Krysko et al., 2003). The Key Biscayne population in Miami-Dade County originated from animals escaped or released from the Crandon Park Zoo when it closed in 1979 (Townsend et al., 2003b; Krysko et al., 2010). This population seems to have remained on Key Biscayne and not spread to the mainland or nearby islands. The dates and invasive pathways of other introductions in Florida are not known. Genetic analyses indicate that ultimately all Florida populations derived from Honduras (Nuñez, 2016).

Origins of introduced populations in Venezuela and on the Colombian islands of Providencia and San Andres are uncertain. In Colombia, first museum collections occurred in before 1933 (Barbour and Shreve, 1934); but introductions by humans to these islands likely occurred many years prior (Dunn, 1945; Rueda-Almonacid, 1999; Forero-Medina et al., 2006). On the other hand, Hedges (1996, p.105) concludes that these island populations “originated by dispersal from Central America in the Quaternary”. In Venezuela, C. similis was first noticed in 1998 inhabiting gardens, parking lots and parks.


Top of page
Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Colombia Central America   Food (pathway cause) Yes Dunn (1945); Forero-Medina et al. (2006); Hedges (1996); Rueda-Almonacid (1999) Introduced to the islands of San Andres and Providencia, probably as a food source. Origin of population is not definitive
Florida Honduras 1979 Pet trade (pathway cause) Yes Krysko et al. (2003); Nuñez (2016) Origin confirmed via genetic analysis
Venezuela 1998 Hitchhiker (pathway cause) Yes Barrio-Amorós and Rivas-Fuenmayor (2008) Presumed arrived with cargo from Central America. If population continues to expand, it could threaten nesting sea turtles

Risk of Introduction

Top of page

Over time, the number of C. similis imported into the USA has declined; just 76 were imported in 2008 (Stephen et al., 2011). However, the presence of thousands of free-living ctenosaurs in Florida means that they can be trapped and moved to new locations. Deliberate releases have occurred on Keeywadin Island, and likely have occurred on Cayo Costa and other islands as well (Krysko et al., 2003).

The recent appearance of ctenosaurs in Venezuela (Barrio-Amorós and Rivas-Fuenmayor, 2008; Flores and Esqueda, 2008), presumably through hitchhiking on ships, demonstrates the on-going potential for the species to spread to new areas.


Top of page

Dry lowland scrub, woodland, grassland, beach dunes. Especially dependent on riparian woodlands in Guanacaste Province, Costa Rica where the 4-6 months dry season restricts vegetation and moisture to the riparian zones (van Devender, 1982). Also frequents mangroves in intertidal areas. Adapts well to disturbed areas, parkland, and human habitation (Henderson, 1973; González-García et al., 2009).

Habitat List

Top of page
Terrestrial – ManagedCultivated / agricultural land Secondary/tolerated habitat Harmful (pest or invasive)
Cultivated / agricultural land Secondary/tolerated habitat Natural
Cultivated / agricultural land Secondary/tolerated habitat Productive/non-natural
Disturbed areas Secondary/tolerated habitat Harmful (pest or invasive)
Disturbed areas Secondary/tolerated habitat Natural
Rail / roadsides Secondary/tolerated habitat Harmful (pest or invasive)
Rail / roadsides Secondary/tolerated habitat Natural
Terrestrial ‑ Natural / Semi-naturalNatural forests Principal habitat Natural
Riverbanks Principal habitat Natural
Rocky areas / lava flows Principal habitat Harmful (pest or invasive)
Rocky areas / lava flows Principal habitat Natural
Scrub / shrublands Principal habitat Harmful (pest or invasive)
Scrub / shrublands Principal habitat Natural
Arid regions Principal habitat Harmful (pest or invasive)
Arid regions Principal habitat Natural
Coastal areas Secondary/tolerated habitat Harmful (pest or invasive)
Coastal areas Secondary/tolerated habitat Natural
Coastal dunes Secondary/tolerated habitat Harmful (pest or invasive)
Coastal dunes Secondary/tolerated habitat Natural
Mangroves Present, no further details
Intertidal zone Present, no further details

Biology and Ecology

Top of page


A phylogeographic study of C. similis throughout its native range is in progress (AS Pasachnik et al., Institute for Conservation Research, San Diego Zoo Global, California, USA, unpublished data).

Genetic analyses of C. similis in Florida, USA, revealed a set of 5 haplotypes (Nuñez, 2016). One haplotype was uniquely associated with the ctenosaurs population in southwestern Florida that ranges from Sarasota southward to Naples, and one came from a specimen found on No Name Key in the Florida Keys. The remaining haplotypes were from populations in Broward and Miami-Dade counties, in southeastern Florida. Each of the 5 haplotypes in Florida was most closely aligned with Honduran populations in the native range of C. similis.

Hybridization between C. similis and C. bakeri has been documented on Utila Island in Honduras (Gutsche and Köhler, 2008; Pasachnik et al. 2009).  

Reproductive Biology

In the introduced population on Gasparilla Island in Florida, USA, testes size peaked mark­edly during January to April, after which there was rapid tes­ticular regression (Avery et al., 2014). Similarly, during January to April, 67.3% of all females contained vitellogenic follicles or oviducal eggs, compared to 3.8% during the rest of the year. During April to June, 81% (199 of 245) of females of reproductive size (>185 mm snout-vent length, SVL), possessed either oviducal eggs, vitellogenic folli­cles, or a convoluted oviduct indicating previous laying. Among females with SVL ≥ 235 mm, 99 of 100 exhib­ited evidence of reproduction. There is no evidence of multiple clutches per year. Clutch size, as determined by the number of oviducal eggs, averaged 31.6 (SE = 1.7). Clutch size with­in size classes did not differ from that recorded in Nicaragua (Fitch and Hen­derson, 1978). Clutch mass (mean ± SE) as a per­centage of female body mass was 18.0% ± 0.7%, and did not vary with SVL.

On Gasparilla Island, hatchlings (minimum 43 mm SVL, 2.75 g body mass) were observed from the last week of July until early October, with 97.5% of the hatchling iguanas encountered in August and September (Avery et al., 2014). Hatchlings exhibited a growth rate of approximately 6.8 mm/month.

Reproduction is seasonal. Egg-laying takes place in the dry season, and hatching occurs just before the onset of the wet season. Thus, in Nicaragua, eggs are laid during February to March and hatching is mostly in June (Fitch and Henderson, 1978). In Florida, USA, egg-laying occurs in April-May, with hatching in July to August (Avery et al., 2014).

Populations of C. similis are female-biased (Fitch and Henderson, 1978). In Florida, 57% of 1321 animals necropsied were female (Avery et al., 2014). One female collected on 27 March 2002 on Key Biscayne had 82 well-developed eggs in her oviducts (Krysko et al. 2003).

Most females reach sexual maturity in their second year at about 200 mm SVL. Clutch size increases steadily with age and size; a maximum clutch of 88 eggs has been reported (Fitch and Henderson, 1978). In Florida, USA, clutch size averaged 32 (n = 56), with a range of 6-62 (Avery et al., 2014).

Physiology and Phenology

The very concentrated breeding season (February to April) characteristic of the species in its na­tive range (Nicaragua; Fitch and Henderson, 1978) oc­curs 2 months later (April to June) in the introduced range (Florida; Avery et al., 2014). C. similis appears to grow more slowly in Florida, USA, than in Central American sites 1500-1800 km farther south. Fitch and Henderson (1978) report that in Nicaragua hatchlings grew to >140 mm SVL and >80 g body mass within 6 months. Hatchlings on Gasparilla Island, Florida grow much more slow­ly, averaging just 91.0 mm SVL and 21.7 g body mass after 6 months.

The Florida population is subjected to a very different tem­perature regime than native C. similis. In par­ticular, mean minimum monthly temperatures in Managua, Nicaragua during winter (December to February) range from 19.7-21.2 °C, whereas on Gasparilla Island during the same months mean monthly temperatures range from 10.9-12.8 °C. The colder winter temperature regime not only reduc­es activity but also limits growth rate and could retard sexual maturation.


In captivity, 22.4 years (The Animal Ageing and Longevity Database, 2016). Estimated maximum observed age of 9 years among free-ranging females (Fitch and Henderson, 1978).

Activity Patterns

Winter activity of introduced populations in Florida is greatly reduced relative to warmer parts of the year.

Population Size and Density

Reportedly common in appropriate habitat throughout most of its range, although some populations can be locally depleted due to exploitation for food and medicinal uses (Savage, 2002). In Parque Nacional Palo Verde, Costa Rica, Mora (2010) reported the population density to be 7.1 ctenosaurs/ha.


The species exhibits an ontogenetic dietary shift as individuals become increasingly more herbivorous with age (van Devender, 1982; Krysko et al., 2009). The shift to plant-dominated diet is accompanied by changes in dentition (Montanucci, 1968). In C. pectinata, this ontogenetic dietary shift is also reflected in the gut morphology of the species (Durtsche, 2000), but similar research has not been conducted on the physiology of C. similis. Regardless, C. similis is a dietary opportunist and will eat whatever it can catch. Even though diets of larger, older individuals consist mostly of plant materials, they are carnivorous when given the chance (Avery et al., 2009).

Natural Food Sources

Top of page
Food SourceLife StageContribution to Total Food Intake (%)Details
Invertebrates: insects, spiders, crabs All Stages 25
Juvenile tortoises All Stages .25
Neonate rodents .5
Plants: leaves, berries, flowers All Stages 70
Small lizards (including conspecifics) 1


Top of page
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Latitude/Altitude Ranges

Top of page
Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)

Natural enemies

Top of page
Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Boa constrictor Predator All Stages not specific
Canis familiaris Predator All Stages not specific
Ctenosaura similis Predator Juveniles not specific
Homo sapiens Predator Adults/Eggs to species
Loxocemus bicolor Predator Eggs not specific
Trimorphodon biscutatus Predator Juveniles to species

Notes on Natural Enemies

Top of page

Hatchlings are preyed upon by conspecifics (Krysko et al., 2009; ML Avery, National Wildlife Research Center, Gainesville, Florida, USA, unpublished data). Boa constrictor and other snakes prey on adult and juvenile ctenosaurs (Mora-Benavides, 1987; Farrollo et al., 2010). In Costa Rica, lyre snakes, Trimorphodon biscutatus, appear to specialize as predators of C. similis (van Devender, 1982).

Means of Movement and Dispersal

Top of page

Natural Dispersal

Daily movements tend to be <100 m (Henderson, 1973; Fitch and Henderson, 1978), but movements up to 200 m by juveniles occur (van Devender, 1982). It is clear that ctenosaurs can disperse short distances on land, and C. similis is capable of swimming. Also, sightings of ctenosaurs along causeways connecting Gasparilla Island to mainland Florida, USA, lend credence to the idea that the species is capable of dispersing unaided from the island.

Accidental Introduction

Short- and long-distance dispersal of C. similis has been facilitated, and probably continues to be, by hitchhiking on vehicles and ships (Krysko et al., 2003; Barrio-Amorós and Rivas-Fuenmayo, 2008). The rate or frequency of such events is unknown, but even a single introduction event can potentially produce serious long-term consequences.

Intentional Introduction

Ctenosaurs have been intentionally transported from their native range to offshore Caribbean islands (Dunn, 1945; Rueda-Almonacid, 1999; Forero-Medina et al., 2006) and to Florida, USA (Krysko et al., 2003). Furthermore, within Florida, subsequent purposeful transport and introductions have exacerbated the potential impacts of ctenosaurs on native fauna (Krysko et al., 2003). Recent genetic analyses confirmed that multiple independent introductions were responsible for the current distribution of C. similis in Florida (Nuñez, 2016).

Pathway Causes

Top of page
CauseNotesLong DistanceLocalReferences
FoodReleased by people from Central America on Providencia and San Andres Islands Yes Dunn, 1945; Forero-Medina et al., 2006; Rueda-Almonacid, 1999
HitchhikerPresumably brought to Venezuela accidentally on cargo ships. Also spread in Florida via vehicles Yes Yes Barrio-Amorós and Rivas-Fuenmayor, 2008; Krysko et al., 2003
Intentional releaseIntentionally transported and released in new places in Florida Yes Krysko et al., 2003
Pet tradeFlorida resident brought 3 ctenosaurs back from Mexico as pets, but then released them on Gasparilla Yes Krysko et al., 2003

Pathway Vectors

Top of page
VectorNotesLong DistanceLocalReferences
Bulk freight or cargoPresumably transported to Venezuela in cargo ships Yes Barrio-Amorós and Rivas-Fuenmayor, 2008
Pets and aquarium speciesBrought as pets to Florida from Mexico Yes Krysko et al., 2003

Impact Summary

Top of page
Cultural/amenity Negative
Environment (generally) Negative

Economic Impact

Top of page

Economic impacts are localized and consist principally of damage to ornamental plants used as landscaping at private residences and community buildings. No estimate of direct economic loss is available. Since 2008, Florida residents in areas beset by populations of C. similis have self-imposed taxes totalling in excess of $250,000 to hire professional trappers to control these invasive animals.

C. similis has caused extensive damage to melon seedlings and chicks (Tasmitt and Valdivieso, 1963).

Environmental Impact

Top of page

Impact on Biodiversity

C. similis on Gasparilla Island, Florida (USA) negatively impacts state threatened gopher tortoises (Gopherus polyphemus) through direct predation (Avery et al., 2009), occupation of tortoise burrows (Engeman et al., 2009), and utiliza­tion of food resources (Krysko et al., 2009). Other burrow- or ground-nesting species of concern, such as the Florida burrowing owl (Athene cunicularia floridana), a species of Special State Concern in Florida, and the federally threatened least tern (Sterna antillarum), are potentially vulnerable to predation, although direct impacts to these species remain to be documented (Krysko et al., 2003).

Threatened Species

Top of page
Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Gopherus polyphemus (gopher tortoise)VU (IUCN red list: Vulnerable) VU (IUCN red list: Vulnerable); USA ESA listing as threatened species USA ESA listing as threatened species; USA ESA candidate species USA ESA candidate speciesFloridaCompetition - monopolizing resources; PredationAvery et al., 2009

Social Impact

Top of page

None documented at this time.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Is a habitat generalist
  • Capable of securing and ingesting a wide range of food
  • Highly mobile locally
  • Benefits from human association (i.e. it is a human commensal)
  • Has high reproductive potential
  • Gregarious
  • Has high genetic variability
Impact outcomes
  • Conflict
  • Negatively impacts agriculture
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Hybridization
  • Predation
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult/costly to control


Top of page

This species is of limited value in the pet trade as it can be aggressive and “difficult” (Stephen et al., 2011). Total imports of C. similis to the US peaked in 2004 (3296 animals), but decreased to 76 by 2008 (Stephen et al., 2011). Illegal international trade involving this and other species of Ctenosaura on the internet is common (Stephen et al., 2011).

In many parts of its native range, C. similis is hunted and sold for food or for traditional medicinal uses. This species is not usually raised in captivity for meat production because, in contrast to Iguana iguana, successful captive rearing of C. similis is very difficult (Stephen et al., 2011).

Uses List

Top of page


  • Botanical garden/zoo
  • Laboratory use

Human food and beverage

  • Meat/fat/offal/blood/bone (whole, cut, fresh, frozen, canned, cured, processed or smoked)

Medicinal, pharmaceutical

  • Traditional/folklore

Similarities to Other Species/Conditions

Top of page

For years, most populations of C. similis in Florida, USA, were misidentified as Ctenosaura pectinata until field collections and close examination of museum specimens revealed the true identity (Townsend et al. 2003b). The two species can be distinguished by three morphological characters (Köhler et al., 2000; Townsend et al., 2003b):

  1. C. similis has 0-12 (mean 0.4) scales separating the dorsal and caudal crests, while C. pectinata has 0-20 (mean 7.2).
  2. C. similis has 2 complete rows of intercalaries between whorls of enlarged caudal scales near the base of the tail, compared to 3 rows in C. pectinata.
  3. C. similis has dark dorsal crossbands which are absent in C. pectinata.

Prevention and Control

Top of page


Prevention is the best approach to invasive species management. Species such as C. similis which are very fecund and dietary generalists are especially problematic as just a few introduced animals can transform into a large, established population in short order.


Physical/mechanical control

The C. similis population on Gasparilla Island, Florida (USA) grew without restraint for over 30 years before being subjected to control measures by professional trappers. Removal strategies included placing bait­ed live traps in shaded areas frequented by ctenosaurs, de­ploying unbaited live traps in the mouths of gopher tortoise burrows where ctenosaurs had entered, and placing unbaited live traps along the base of walls or other bar­riers where ctenosaurs travelled. Trappers employed com­mercial live traps with 2.54 × 2.54 cm or 1.27 × 2.54 cm mesh and baited with fresh cantaloupe or watermelon. Trappers dispatched captured lizards with a pistol load­ed with birdshot or .22 caliber bullets. Field personnel shot iguanas when prudent and safe during regular pa­trols of the study area using a .22 caliber rifle or air rifle (Avery et al., 2014). These removal efforts were highly successful as >20,000 ctenosaurs have been removed since 2008, and control efforts remain in effect.  

Chemical control

Possible methods for controlling C. similis using chemical toxicants were investigated. Captive ctenosaurs readily ingested sweet, red artificial baits into which capsules of toxicant were placed. Zinc phosphide was the most efficacious material tested, but application of a field baiting strategy employing toxic bait is dependent on development of target-specific delivery methods which are currently not available (Avery et al., 2011).

Monitoring and Surveillance

Increased biosecurity measures to detect and remove ctenosaurs potentially hitch-hiking on cargo ships would help prevent accidental introductions such as recently occurred in Venezuela (Barrio-Amorós and Rivas-Fuenmayor, 2008). Additionally, increased scrutiny of international trade in C. similis and similar species is needed to counteract illegal movements of these animals across borders.

Gaps in Knowledge/Research Needs

Top of page

Rather than devote more resources, time, and personnel to studying the introduced populations there should be greater emphasis on removing them. This seems particularly true in Florida, USA, and Venezuela where populations are still manageable and eradication/extirpation is possible with dedicated, persistent management efforts.


Top of page

Anderson C; Enge KM, 2012. Geographic distribution: Ctenosaura similis (Gray's spiny-tailed iguana). Herpetological Review, 42(4):568.

Avery ML; Eisemann JD; Keacher KL; Savarie PJ, 2011. Acetaminophen and zinc phosphide for lethal management of invasive lizards Ctenosaura similis. Current Zoology, 57(5):625-629.

Avery ML; Tillman EA; Krysko KL, 2009. Gopherus polyphemus (gopher tortoise), Ctenosaura similis (Gray's spiny-tailed iguana) predation. Herpetological Review, 40(4):435.

Avery ML; Tillman EA; Spurfeld C; Engeman RM; Maciejewski KP; Brown JD; Fetzer EA, 2014. Invasive black spiny-tailed iguanas (Ctenosaura similis) on Gasparilla Island, Florida, USA. Integrative Zoology, 9(5):590-597.

Barbour T; Shreve B, 1934. A new race of rock iguana. Occasional Papers of the Boston Society of Natural History, 8:197-198.

Barrio-Amorós CL; Rivas-Fuenmayor G, 2008. Spiny-tailed iguanas (Ctenosaura similis) in Venezuela: a preliminary report. Iguana, 15(3):161.

Butterfield BP; Meshaka Jr WE; Guyer C, 1997. Nonindigenous amphibians and reptiles, strangers in paradise: impact and management of non-indigenous species in Florida. Island Press. Washington D.C., USA 123-137.

Devender RW van, 1982. Growth and ecology of spiny-tailed and green iguanas in Costa Rica, with comments on the evolution of herbivory and large body size. In: Iguanas of the world: their behavior, ecology, and conservation [ed. by Burghardt GM, Rand A]. Park Ridge, New Jersey, USA: Noyes Publications, 162-183.

Dunn ER, 1945. The amphibians and reptiles of the Colombian Caribbean islands San Andres and Providencia. Caldasia, 3(14):363-365.

Durtsche RD, 2000. Ontogenetic plasticity of food habits in the Mexican spiny-tailed iguana, Ctenosaura pectinata. Oecologia, 124(2):185-195.

Enge KM; Krysko KL; Borgia AP, 2006. Geographic distribution: Ctenosaura similis (black spiny-tailed iguana). Herpetological Review, 37(4):494.

Engeman RM; Kennedy M; Constantin BU; Christie ML; Hall PT, 2009. Ctenosaura similis (black spinytail iguana), Gopherus polyphemus (gopher tortoise) concurrent burrow use. Herpetological Review, 40(1):84.

Farallo VR; Sasa M; Wasko DK; Forstner MRJ, 2010. Reduced foraging in the presence of predator cues by the Black Spiny-tailed Iguana, Ctenosaura similis (Sauria: Iguanidae). Phyllomedusa - Journal of Herpetology, 9(2):109-119.

Fitch HS; Hackforth-Jones J, 1983. Ctenosaura similis (garrobo, iguana negra, ctenosaur). In: Costa Rican Natural History [ed. by Janzen DH]. Chicago and London: University of Chicago Press, 394-396.

Fitch HS; Henderson RW, 1978. Ecology and exploitation of Ctenosaura similis. University of Kansas Science Bulletin, 51(15):483-500.

Flores D; Esqueda LF, 2008. First record of the spiny-tailed Iguana Ctenosaura similis (Gray, 1831) (Squamata: Iguanidae) in Venezuela. Herpetotropicos, 4(1):41.

Forero-Medina G; Castano-Mora OV; Rodriguez-Melo M, 2006. Ecologia de Caiman crocodilus fuscus en San Andres Isla, Colombia: un studio preliminar. Caldasia, 28(1):115-124.

González-García A; Belliure J; Gómez-Sal A; Dávila P, 2009. The role of urban greenspaces in fauna conservation: the case of the iguana Ctenosaura similis in the 'patios' of León city, Nicaragua. Biodiversity and Conservation, 18(7):1909-1920.

Gutsche A; Kohler F, 2008. Phylogeography and hybridization in Ctenosaura species (Sauria, Iguanidae) from Caribbean Honduras: insights from mitochondrial and nuclear DNA. Zoosystematics and Evolution, 84(2):245-253.

Hedges SB, 1996. The origin of West lndian amphibians and reptiles. Contributions to West Indian herpetology: a tribute to Albert Schwartz, 12 [ed. by Powell R, Henderson RW]. Ithaca, New York: Society for the Study of Amphibians and Reptiles Contributions to Herpetology, 95-128.

Henderson RW, 1973. Ethnoecological observations of Ctenosaura similis (Sauria: Iguanidae) in British Honduras. Journal of Herpetology, 7(1):27-33.

Iguana Taxonomy Working Group, 2011. Iguanas of the world (Iguanidae: Iguaninae).

Kohler G; Schroth W; Streit B, 2000. Systematics of the Ctenosaura group of lizards (Reptilia: Sauria: Iguanidae). Amphibia-Reptilia, 21(2):177-191.

Krysko KL; Burgess JP; Rochford MR; Gillette CR; Cueva D; Enge KM; Somma LA; Stabile JL; Smith DC; Wasilewski JA; Kieckhefer IIIGN; Granatosky MC; Nielsen SV, 2011. Verified non-indigenous amphibians and reptiles in Florida from 1863 through 2010: outlining the invasion process and identifying invasion pathways and stages. Zootaxa, 3028:1-64.

Krysko KL; Enge KM; Donlan EM; Golden EA; Burgess JP; Larson KW, 2010. The non-marine herpetofauna of Key Biscayne, Florida. Herpetological Conservation and Biology, 5(1):132-142.

Krysko KL; Enge KM; Moler PE, 2011. Atlas of amphibians and reptiles in Florida. Final report, project agreement 08013. Tallahassee, Florida, USA: Florida Fish and Wildlife Conservation Commission, 524 pp.

Krysko KL; King FW; Enge KM; Reppas AT, 2003. Distribution of the introduced black spiny-tailed iguana (Ctenosaura similis) on the southwestern coast of Florida. Florida Scientist, 66(2):74-79.

Krysko KL; Larson KW; Diep D; Abellana E; McKercher ER, 2009. Diet of the nonindigenous black spiny-tailed iguana, Ctenosaura similis (Gray 1831) (Sauria: Iguanidae), in southern Florida. Florida Scientist, 72(1):48-58.

Köhler G, 2003. Reptiles of Central America. Offenbach, Germany: Herpeton, 379 pp.

Montanucci RR, 1968. Comparative dentition in four iguanid lizards. Herpetologica, 24(4):305-315.

Mora JM, 2010. Natural history of the black spiny-tailed iguana (Ctenosaura similis) at Parque Nacional Palo Verde, Costa Rica, with comments on the conservation of the genus Ctenosaura. In: Conservation of Mesoamerican amphibians and reptiles [ed. by Wilson LD, Townsend JH, Johnson J]. Utah, USA: Eagle Mountain Publishing, 716-734.

Mora-Benavides JM, 1987. Predation by Loxocemus bicolor on the eggs of Ctenosaura similis and Iguana iguana. Journal of Herpetology, 21(4):334-335.

Nuñez LP, 2016. Molecular analyses of three non-indigenous squamate species in Florida: testing hypotheses of introduction pathways, species identity, and native range origins. MS Thesis. Gainesville, Florida, USA: University of Florida.

Pasachnik SA; Fitzpatrick BM; Near TJ; Echternacht AC, 2009. Gene flow between an endangered endemic iguana, and its wide spread relative, on the island of Utila, Honduras: when is hybridization a threat? Conservation Genetics, 10(5):1247-1254.

Rueda-Almonacid JV, 1999. Current situation and problems generated by the introduction of " bullfrog " to Colombia. (Situacion actual y problematica generada por la introduccion de "rana toro" a Colombia.) Revista de la Academia Colombiana de Ciencias Exactas, Fisicas y Naturales, 23 (suplemento especial). 367-393.

Savage JM, 2002. The Amphibians and Reptiles of Costa Rica: a herpetofauna between two continents, between two seas. Chicago, Illinois, USA: University of Chicago Press, 934 pp.

Stephen C; Pasachnik S; Reuter A; Mosig P; Ruyle L; Fitzgerald L, 2011. Survey of status, trade, and exploitation of Central American iguanas.

Tamsitt JR; Valdivieso D, 1963. The herpetofauna of the Caribbean islands San Andre and Providencia. Revista de Biologia Tropical, 11(2):131-139.

The Animal Ageing and Longevity Database, 2016. Ctenosaura similis. Human Ageing Genomic Resources.

The Reptile Database, 2016. Ctenosaura similis (GRAY, 1831). The Reptile Database.

Townsend JH; Krysko KL; Enge KM, 2003. Introduced iguanas in southern Florida: more than 35 years of establishment and range expansion. Iguana, 10(4):111-118.

Wilson LD; Porras L, 1983. The ecological impact of man on the South Florida herpetofauna. University Kansas Museum of Natural History Special Publication, 9. 1-89.


Top of page

08/06/2016 Original text by:

Michael Avery, USDA/Wildlife Services, USA

Distribution Maps

Top of page
You can pan and zoom the map
Save map