Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Boa imperator
(Central American Boa)

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Datasheet

Boa imperator (Central American Boa)

Summary

  • Last modified
  • 10 October 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Boa imperator
  • Preferred Common Name
  • Central American Boa
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Chordata
  •       Subphylum: Vertebrata
  •         Class: Reptilia
  • Summary of Invasiveness
  • Boa imperator was formerly one of six recognized subspecies of the large constricting snake B. constrictor, but has been elevated to species status as B. imperator, occurring west of the Andes...

  • Principal Source
  • Draft datasheet under review

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Pictures

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PictureTitleCaptionCopyright
Boa imperator; adult. Captive specimen. Laboratorio de Herpetologia, Medellin, Antioquia, Colombia.
TitleAdult
CaptionBoa imperator; adult. Captive specimen. Laboratorio de Herpetologia, Medellin, Antioquia, Colombia.
Copyright©Esteban Alzate/via wikipedia - CC BY-SA 2.5
Boa imperator; adult. Captive specimen. Laboratorio de Herpetologia, Medellin, Antioquia, Colombia.
AdultBoa imperator; adult. Captive specimen. Laboratorio de Herpetologia, Medellin, Antioquia, Colombia.©Esteban Alzate/via wikipedia - CC BY-SA 2.5
Boa imperator; adult, in habitat. Also known as the Arabesque Boa or Central American Boa. Osa Peninsula, Costa Rica.
TitleAdult
CaptionBoa imperator; adult, in habitat. Also known as the Arabesque Boa or Central American Boa. Osa Peninsula, Costa Rica.
Copyright©Dick Culbert/via wikipedia (and flickr) - CC BY 2.0
Boa imperator; adult, in habitat. Also known as the Arabesque Boa or Central American Boa. Osa Peninsula, Costa Rica.
AdultBoa imperator; adult, in habitat. Also known as the Arabesque Boa or Central American Boa. Osa Peninsula, Costa Rica.©Dick Culbert/via wikipedia (and flickr) - CC BY 2.0

Identity

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Preferred Scientific Name

  • Boa imperator Daudin, 1803

Preferred Common Name

  • Central American Boa

Other Scientific Names

  • Boa constrictor imperator Daudin, 1803
  • Boa constrictor longicauda Price and Russo, 1991
  • Boa constrictor sabogae Forcart, 1951
  • Boa constrictor var. isthmica Garman, 1883
  • Boa diviniloquax var. mexicana Jan, 1863
  • Boa eques Eydoux and Souleyet, 1842
  • Boa imperator longicauda Hynková et al., 2009
  • Boa imperator sabogae Hynková et al., 2009
  • Boa mexicana Garman, 1883
  • Constrictor constrictor imperator Ihering, 1911
  • Constrictor constrictor sabogae Barbour and Loveridge, 1929
  • Constrictor constrictor sigma Smith, 1943
  • Epicrates sabogae Barbour, 1906

International Common Names

  • English: Arabesque boa

Summary of Invasiveness

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Boa imperator was formerly one of six recognized subspecies of the large constricting snake B. constrictor, but has been elevated to species status as B. imperator, occurring west of the Andes Mountains from Ecuador in northwestern South America northwards to southeastern Mexico in North America (populations in northern Mexico are now considered to be B. sigma), and including the two subspecies B. c. longicauda and B. c. sabogae (although this recent change has not been universally accepted).  Because many historical introduction reports do not specify the subspecies of B. constrictor, or the locality of origin, the data presented in this datasheet on introductions are likely to be an underrepresentation; recorded distributions may change as further genetic information becomes available. B. imperator has been widely transported as part of the pet trade, but only occasionally escaped or been released. It has been intentionally introduced to the island of Cozumel, Mexico, and intentionally or accidentally (often in the pet trade or as a stowaway in cargo) introduced to various states of the USA, but it is not currently known to have formed any established breeding populations in the USA.  The main ecological impacts of B. imperator are currently on native animals upon which it preys, including birds, lizards, and mammals; in particular it is believed to be a threat to the Critically Endangered Cozumel Thrasher (Toxostoma guttatum) on Cozumel Island. In Florida it is a potential threat to the threatened Gopher Tortoise (Gopherus polyphemus), by competing for the use of its burrows. B. imperator is itself listed on CITES Appendix II, which includes species not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization incompatible with their survival.  The primary causes of declines are overharvesting and habitat loss and degradation.  

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Chordata
  •             Subphylum: Vertebrata
  •                 Class: Reptilia
  •                     Order: Serpentes
  •                         Family: Boidae
  •                             Genus: Boa
  •                                 Species: Boa imperator

Notes on Taxonomy and Nomenclature

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Boa imperator was formerly one of six recognized subspecies of B. constrictor.  It has been elevated to species status as B. imperator, occurring west of the Andes Mountains from Ecuador in northwestern South America northward to Mexico in North America, and including the two subspecies B. c. longicauda and B. c. sabogae (Hynková et al., 2009). This elevation was made in the light of a study using 1114 bp of mtDNA (cytochrome b) sequence data among mostly captive bred individuals of B. constrictor, which suggested that it was likely to be a species complex made up of at least two distinct genetic lineages with 5-7% sequence divergence between them. For more details, see the ‘Genetics’ section under ‘Biology and Ecology’. Although the elevated species name has not been extensively accepted because it uses only a single locus and because there are a number of outlier samples, it is recognized by Reynolds et al. (2013, 2014), Solis et al. (2014), Suárez-Atilano et al. (2014), Sunyer (2014), McCranie (2015) and Card et al. (2016).

Suárez-Atilano et al. (2014) examined 1063 bp of cytochrome b and nuclear DNA sequence and microsatellite data among 149 samples from the B. imperator lineage and found two main additional lineages, one occuring along the Pacific coast in Mexico and the other along the Caribbean coast from the Yucatán peninsula southward through Central America to Panama.  They also found structure within these two lineages, suggesting even more recent diversifications.  Card et al. (2016) found three main lineages roughly corresponding to the three primary land masses of the Western Hemisphere, supporting those found by Hynková et al. (2009) and Suárez-Atilano et al. (2014).  They recognized these three lineages as B. constrictor from Argentina northward to Colombia in South America, B. imperator from western Colombia northward through central America to southeastern Mexico in North America, and B. sigma (a resurrected and elevated name) from the Pacific coast of Mexico eastward to the Isthmus of Tehuantepec.

Because many historical introduction reports do not specify the subspecies of B. constrictor (see Kraus, 2009), or the locality of origin, the data presented in this datasheet on introductions are likely to be an under-representation. Recorded distributions may change as further genetic information becomes available.

Description

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B. imperator is a large sized snake species, but its recent elevation to species status means that there is a lack of data on exactly how big it is.  Adult females are larger than males both in length and girth. Males have 2 enlarged spurs along the sides of the cloaca and have longer tails than females. Coloration varies greatly but the ground colour is usually grey, brown, black, or salmon.  There is a dark stripe that extends from the top of the eye both forward toward the snout and backward and diagonally toward the jaw.  Dorsal blotches are present on the entire dorsum and tail, and tail blotches are reddish.  Juveniles usually have brighter colorations, which tend to darken with age.  On the Cayos Cochinos (Hog Islands), Honduras, the species is smaller and typically more lightly colored and hypomelanistic, with a salmon pink to orange coloured tail (Reed et al., 2007).  In Belize, island populations have a shorter body and a longer head and larger eyes than mainland populations (Boback and Carpenter, 2007).

In Miami, Florida, 140 boas collected between 1992 and 2011 measured between 25 and 295 cm in total length and weighed between 0.05 and 16.3 kg, although these were probably mostly B. constrictor (K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data; Snow et al., 2007).

Distribution

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B. imperator is native to Central America from southeastern Mexico southward to Ecuador in South America (Hynková et al., 2009).  Reports from northern Mexico (e.g. Baltosser, 1982) refer to the population now considered to be B. sigma (Card et al., 2016). Because of its coloration, size, and ease in captivity, it is popular in the pet trade and has occasionally been introduced elsewhere via escaped individuals and intentional releases.  Because many historical introduction reports do not specify the subspecies of B. constrictor (see Kraus, 2009), the data presented in this datasheet on introductions are likely to be an under-representation; recorded distributions may change as further genetic information becomes available.  B. imperator was intentionally introduced to the island of Cozumel, Mexico, in 1971 (López-González, 1991; Martínez-Morales and Cuarón, 1999).  In the USA, Boa sp. was introduced as a stowaway in cargo in Iowa and Minnesota (Guthrie, 1923; Kraus, 2009), either introduced or intercepted before escaping in Kentucky (Allen, 1928), but it is established only in Florida (K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data; Snow et al., 2007; Crother, 2017).  Boa sp. was introduced via the pet trade to many areas in Florida from the 1960s onwards, and this is likely to have included B. imperator, but the first genetically confirmed B. imperator were found on Big Pine Key in 2009 and in Miami in 2014, and unlike B. constrictor, B. imperator is not currently known to have established any breeding populations in Florida. (K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data). B. imperator (as B. c. imperator) has been reported as invasive in Puerto Rico (ISSG, 2017), but a genetic study has shown that the established population in Mayagüez consists entirely of B. constrictor, whereas the only specimen of B. imperator is a single waif from a different part of the island (Reynolds et al., 2013). 

Distribution Table

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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

MexicoLocalisedNative Invasive López-González, 1991; Martínez-Morales and Cuarón, 1999; Hynková et al., 2009; Card et al., 2016Native and non-invasive in the south-eastern part of the country; introduced and invasive on the island of Cozumel
USA
-FloridaLocalisedIntroduced Not invasive K. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished dataIntroduced to Florida but unlike B. constrictor, not known to be established as a breeding species
-IowaAbsent, formerly presentIntroduced1914 Not invasive Guthrie, 1923
-KentuckyAbsent, formerly presentIntroduced1928 Not invasive Allen, 1928
-MinnesotaAbsent, formerly presentIntroduced1890s Not invasive Guthrie, 1923

Central America and Caribbean

Costa RicaWidespreadNative Not invasive Hynková et al., 2009
El SalvadorWidespreadNative Not invasive Hynková et al., 2009
GuatemalaWidespreadNative Not invasive Hynková et al., 2009
HondurasWidespreadNative Not invasive Hynková et al., 2009
NicaraguaWidespreadNative Not invasive Hynková et al., 2009
PanamaWidespreadNative Not invasive Hynková et al., 2009
Puerto RicoAbsent, formerly presentIntroduced Not invasive Reynolds et al., 2013A single specimen found

South America

ColombiaWidespreadNative Not invasive Hynková et al., 2009
EcuadorWidespreadNative Not invasive Hynková et al., 2009

History of Introduction and Spread

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B. imperator has been widely transported as part of the pet trade, but only occasionally escaped or been released (Kraus, 2009; Reynolds et al., 2013; K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data).

B. imperator was intentionally introduced to the island of Cozumel, Mexico, in 1971 during the production of the Mexican film “El jardín de tía Isabel” (López-González, 1991; Martínez-Morales and Cuarón, 1999). Between 10 and 30 individuals were originally released around the beaches of Palancar to the southwest and between Xlapac and Punta Molas to the northeast, but the species is now found throughout the island (Martínez-Morales and Cuarón, 1999; Vázquez-Domínguez et al., 2012).

Boa sp. was introduced via the pet trade to many areas in Florida from the 1960s onwards, and this is likely to have included B. imperator, but the first genetically confirmed B. imperator were found on Big Pine Key in 2009 and in Miami in 2014, and unlike B. constrictor, B. imperator is not currently known to have established any breeding populations in Florida (K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data).

There are reports from the early 20th century of boas being introduced to a few other US states as stowaways in cargo, but there are no established populations resulting from this.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Mexico Mexico 1971 Intentional release (pathway cause) Yes No López-González (1991); Martínez-Morales and Cuarón (1999) Introduced from the mainland to the island of Cozumel during the making of a film
Iowa 1914 Hitchhiker (pathway cause) No No Guthrie (1923); Kraus (2009) As stowaway in cargo
Minnesota 1890s Hitchhiker (pathway cause) No No Guthrie (1923); Kraus (2009) As stowaway in cargo
Kentucky 1928 Hitchhiker (pathway cause) No No Allen (1928) As stowaway in cargo
Florida 1960s Pet trade (pathway cause) No No Meshaka et al. (1994); Krysko and Sheehy (2005); K. Krysko; Florida Museum of Natural History; Gainesville; Florida; USA; unpublished data
Puerto Rico 2010s Pet trade (pathway cause) No No Reynolds et al. (2013)

Risk of Introduction

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Although adult B. imperator are large, the species has been introduced as stowaways in banana cargo shipments (Guthrie, 1923; Allen, 1928).  More commonly, it is frequently kept in captivity by pet fanciers and sometimes escapes or is intentionally released to establish new populations (King and Krakauer, 1966; Kraus et al., 2012; Kraus and Preston, 2012).

Habitat

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B. imperator is found in lowland tropical deciduous forest from sea level up to 1500 m in lowland scrub forests, rain forests and cloud forests (Savage, 2002; Lemos-Espinal and Smith, 2007; Lemos-Espinal and Dixon, 2013). Introduced Boa spp. in Florida have also been found in grasslands, urban areas, other human-altered habitats, riverbanks, coastal dunes, tropical hammocks, pine rocklands and coastal dunes (Snow et al., 2007).

On Cozumel island, Mexico, it is found in tropical semi-deciduous forest, low tropical deciduous forest, and mangroves; it has been found on the ground, in the lower branches of trees and shrubs (up to 1.5 m above the ground), and in a seasonal pond (about 1.5 m in diameter and 10 cm deep) (Martínez-Morales and Cuarón, 1999; Vázquez-Domínguez et al., 2012). 

Habitat List

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CategoryHabitatPresenceStatus
Freshwater
Ponds Present, no further details Harmful (pest or invasive)
Littoral
Coastal areas Secondary/tolerated habitat Harmful (pest or invasive)
Coastal dunes Secondary/tolerated habitat Harmful (pest or invasive)
Mangroves Secondary/tolerated habitat Harmful (pest or invasive)
Terrestrial-managed
Disturbed areas Principal habitat Harmful (pest or invasive)
Disturbed areas Principal habitat Natural
Managed forests, plantations and orchards Secondary/tolerated habitat Natural
Urban / peri-urban areas Present, no further details Harmful (pest or invasive)
Terrestrial-natural/semi-natural
Natural forests Principal habitat Natural
Natural grasslands Principal habitat Natural
Riverbanks Principal habitat Natural

Biology and Ecology

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Genetics

Hynková et al. (2009) examined 1114 bp of mtDNA (cytochrome b) sequence data among mostly captive bred individuals of B. constrictor, and suggested that it was likely to be a species complex made up of at least two distinct genetic lineages with 5–7% sequence divergence between them.  One lineage generally occurs east of the Andes Mountains in South America from Colombia southward to Argentina, although there were also two outlying samples [NIC2 and LONG4] of the same lineage from unconfirmed localities in Nicaragua and northern Peru, respectively. The other lineage generally occurs west of the Andes from Ecuador in northwestern South America northward to Mexico in North America, although there were also two outlying samples [LONG2, 3, 5 = B. c. longicauda] of this lineage from unconfirmed localities in northern Peru (Hynková et al., 2009).  These five outliers might be due to intergradation (or hybridization, depending on the taxonomy used) resulting from pet fanciers and their erroneous pedigrees and labelling (Hynková et al., 2009).  Nonetheless, Hynková et al. (2009) suggested that the northern lineage be elevated to the species B. imperator and include the two subspecies longicauda and sabogae.  Although this elevated species name has not been extensively accepted because it uses only a single locus and because of the outlier samples mentioned above, it is recognized by Reynolds et al. (2013, 2014), Solis et al. (2014), Suárez-Atilano et al. (2014), Sunyer (2014), McCranie (2015) and Card et al. (2016)

Suárez-Atilano et al. (2014) examined 1063 bp of cytochrome b and nuclear DNA sequence and microsatellite data among 149 samples from the B. imperator lineage and found two main additional lineages.  One lineage occurs along the Pacific coast in Mexico, and the other along the Caribbean coast from the Yucatán peninsula southward through Central America to Panama.  Suárez-Atilano et al. (2014) stated that these two lineages should be recognized as Evolutionarily Significant Units, and suggested that they could also be recognized as distinct species but that this should first be confirmed using coalescent species-delimitation methods.  They also found structure within these two lineages, suggesting even more recent diversifications.

Card et al. (2016) examined 1059 bp of cyt b, and double digest Restriction-site Associated DNA sequencing (RADseq) data, among 305 samples of both wild-collected and pet trade individuals.  They found three main lineages roughly corresponding to the three primary land masses of the Western Hemisphere, supporting those found by Hynková et al. (2009) and Suárez-Atilano et al. (2014).  They recognized these three lineages as B. constrictor from Argentina northward to Colombia in South America, B. imperator from western Colombia northward through central America to southeastern Mexico in North America, and B. sigma from the Pacific coast of Mexico eastward to the Isthmus of Tehuantepec. 

Regarding introduced populations, Vázquez-Domínguez et al. (2012) examined microsatellites in introduced populations on the island of Cozumel, Mexico, and found moderately high levels of heterozygosity.  Reynolds et al. (2013) examined 1067 bp of cytochrome b sequence and microsatellite data to illustrate that the established introduced population of boas in Mayagüez, Puerto Rico, USA, represents a single haplotype corresponding to B. c. constrictor, and a single waif from a different part of the island (San Juan) corresponds to B. imperator.  Another study examined 1067 bp of cytochrome b sequence from introduced snakes in Florida, USA, and suggested that the geographic origins of Florida individuals correspond to both native range genetic lineages, B. constrictor and B. imperator; further investigation indicated that the only established population, at the Charles Deering Estate in Miami, was genetically B. constrictor (K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data).

Reproductive Biology

B. imperator is ovoviviparous; it gives birth to 12-64 young, 40-50 cm long (Campbell, 1999; Lemos-Espinal and Dixon, 2013).

Boa populations in Florida tend to breed during the dry season in April-May, and parturition occurs in July-August; southern hemisphere populations breed at the corresponding times of year in their hemisphere.

Longevity

B. imperator can live up to 40 years in captivity (Cotswold Wildlife Park and Gardens, 2012).

Activity Patterns

B. imperator is primarily nocturnal when it hunts but it will occasionally bask during the day, especially when it is cool (Lemos-Espinal and Dixon, 2013).  On Cozumel island, Mexico, it was frequently found during the day during transects aimed at finding birds (Martínez-Morales and Cuarón, 1999; Vázquez-Domínguez et al., 2012).  On Ometepe Island, Nicaragua, displaced boas moved more than resident boas after they were initially released and moved greater distances with each movement, mainly towards their site of initial capture, suggesting homing ability (Holtzman et al., 2007).

Population Size and Structure

On Cozumel, Mexico, the number of boas observed during diurnal line transect sampling represented an encounter rate of 1.8 boas for every 100 km of forest surveyed (or approximately 1.8 for every 100 hours walking transects) (Martínez-Morales and Cuarón, 1999).

Nutrition

In its native range, B. imperator feeds on a large variety of animals, including iguanas, birds, and mammals such as monkeys, ocelots, deer, agoutis, raccoons, opossums, coatis, tree porcupines, anteaters, rabbits, squirrels, rats, mice, bats and dogs (Greene, 1983; Campbell, 1999; Solórzano, 2004; Reed et al., 2007; Lemos-Espinal and Dixon, 2013).  In Florida, Boa spp. feed on mammals, including grey squirrels (Sciurus carolinensis), opossums, (Didelphis virginiana), and presumably feral cats (Snow et al., 2007).

Environmental Requirements

B. imperator requires sunny areas to bask, but also microhabitats that allow it to seek refuge, such as burrows or dense vegetation.  These latter habitats enable it to escape extreme high and low temperatures.

Natural Food Sources

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Food SourceLife StageContribution to Total Food Intake (%)Details
Birds Other/All Stages
Caribbean Dove, Leptotila jamaicensis
Lizards Other/All Stages
Mammals Other/All Stages
Grey squirrel, Sciurus carolinensis Other/Adult Female/Other/Adult Male
Opossum, Didelphis virginiana Other/Adult Female/Other/Adult Male

Climate

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ClimateStatusDescriptionRemark
Af - Tropical rainforest climate Preferred > 60mm precipitation per month
As - Tropical savanna climate with dry summer Tolerated < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Tolerated < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
A - Tropical/Megathermal climate Preferred Average temp. of coolest month > 18°C, > 1500mm precipitation annually

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
22.8 3.8

Air Temperature

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Parameter Lower limit Upper limit
Mean maximum temperature of hottest month (ºC) 29
Mean minimum temperature of coldest month (ºC) 13

Notes on Natural Enemies

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TEST DATA

Means of Movement and Dispersal

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Accidental Introduction

In the early 20th century B. imperator was accidentally introduced as a stowaway in cargo to the US states of Iowa, Minnesota (Guthrie, 1923; Kraus, 2009) and Kentucky (Allen, 1928); more recently it was found as an escaped pet in San Juan, Puerto Rico (Reynolds et al., 2013) and Florida (Krysko et al., 2011). However, there are no established populations in these locations.

Intentional Introduction

B. imperator was intentionally introduced to the island of Cozumel, Mexico, in 1971, during the making of a film, and spread throughout the island over the next 25 years (López-González, 1991; Martínez-Morales and Cuarón, 1999).  Boas were intentionally introduced to the Charles Deering Estate in Miami, Florida, USA, in the 1960s, but recent genetic studies have shown that the firmly established population there is B. constrictor (Dalrymple, 1994; Snow et al., 2007; K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data). 

Pathway Causes

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CauseNotesLong DistanceLocalReferences
HitchhikerAccidental as stowaway in cargo Yes Guthrie, 1923
Intentional releaseOne instance was as part of the making of a film Yes López-González, 1991
Pet trade Yes Dalrymple, 1994

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Bulk freight or cargoTransported as a stowaway in cargo Yes Guthrie, 1923

Impact Summary

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CategoryImpact
Economic/livelihood Negative
Environment (generally) Negative

Economic Impact

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Thousands of dollars have been spent removing boas, including those known to be B. imperator, from southern Florida (Snow et al., 2007; K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data).

Fear of snakes could have a negative effect on tourism; there are reports of people not wanting to visit Florida because of the presence of large pythons. Fortunately boas are not widespread in Florida (K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished information).

Environmental Impact

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Impact on Biodiversity

In its native range, B. imperator feeds on a large variety of animals.  On Cozumel island, Mexico, it has become one of the most abundant and widely distributed terrestrial vertebrates and is jeopardizing a highly vulnerable insular ecosystem (Vázquez-Domínguez et al., 2012); among other species, it is known to consume the Caribbean Dove, Leptotila jamaicensis (Martínez-Morales and Cuarón, 1999), and it is believed to be a threat to the Critically Endangered Cozumel Thrasher (Toxostoma guttatum) (IUCN, 2016).  In Florida, Boa spp. feed on a variety of mammals; their main ecological impacts are currently on native animals that may be consumed as prey, and on the threatened Gopher Tortoise (Gopherus polyphemus) with which they compete for burrows (Snow et al., 2007).

Threatened Species

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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 resourcesSnow et al., 2007
Toxostoma guttatum (Cozumal thrasher)CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered)MexicoPredationIUCN, 2016

Social Impact

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Being fearful of snakes is mostly irrational, especially with regard to non-venomous species.  Nonetheless, many people are afraid of snakes, which could cause them to panic when a snake is encountered, especially a large non-native one like B. imperator.

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
  • Tolerant of shade
  • Capable of securing and ingesting a wide range of food
  • Highly mobile locally
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Has high genetic variability
Impact outcomes
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Predation
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately
  • Highly likely to be transported internationally illegally
  • Difficult to identify/detect in the field
  • Difficult/costly to control

Uses

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Economic Value

B. imperator is widely traded as a pet; captive-born neonates currently sell for about 200 US dollars each. As an example, from 1979 to 1993, a minimum of 5000 boas were removed from Cayos Cochinos, Honduras, mostly for the pet trade (Reed et al., 2007).  Although some of these populations are protected, collection for the pet trade continues on many islands (Reed et al., 2007).

Uses List

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General

  • Botanical garden/zoo
  • Laboratory use
  • Pet/aquarium trade

Detection and Inspection

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B. imperator utilizes slow movements and cryptic coloration to blend into the surrounding environment.

Although it has in the past been introduced as a stowaway in banana cargo shipments (Guthrie, 1923; Allen, 1928), closer inspection of cargo could reduce or eliminate this pathway of invasion.

Similarities to Other Species/Conditions

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B. imperator is distinguished from B. constrictor primarily by being smaller in size and having a darker tail in the adult stage.

Prevention and Control

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Eradication

An ongoing boa eradication program at the Charles Deering Estate in Miami is being conducted by staff from Zoo Miami and the Miami-Dade Co. Parks, Recreation, and Open Spaces Department. Well over 100 boas have been removed; most are probably B. constrictor, although it is possible that there were some B. imperator among them (K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished data).

Physical/Mechanical Control

Boas found in Florida are physically removed, when workers happen to find them while carrying out their main tasks -- dense vegetation makes it impracticable to look for them intentionally (K.L. Krysko, Florida Museum of Natural History, Gainesville, Florida, USA, unpublished information).

Gaps in Knowledge/Research Needs

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Although many aspects of the natural history of Boa constrictor (sensu lato) have been reported, data are needed specifically for B. imperator on population density, movement patterns, etc., especially in its introduced range.  A phylogeographic analysis using multiple mtDNA and nuclear loci (see Reynolds et al., 2014) would allow for a better understanding of this species complex and allow for more accurate knowledge of the geographic origins of introduced individuals.

References

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Principal Source

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Draft datasheet under review

Contributors

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13/03/17: Original text by:

Kenneth Krysko, Florida Museum of Natural History, Gainesville, Florida, USA

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