Iguana delicatissimaWest Indian Iguana, Lesser Antillean Iguana

Geographic Range

Lesser Antillean iguanas (Iguana delicatissima) are native to the neotropical region, inhabiting the Lesser Antilles, a group of islands in the Caribbean Sea. They are found on Anguilla, St. Barthélémy, St. Eustatius, La Désirade, Dominica, Martinique, Guadeloupe, Les Îles des Saintes and St. Lucia Islands.

Their historical range extended to St. Maarten, Barbuda, St. Christopher, Nevis, Antigua, and Marie-Galante, but they have since been extirpated. (Martin, et al., 2015; Powell, 2004; van Wagensveld, 2015)

Habitat

Lesser Antillean iguanas can thrive in a vast range of environments including mangroves, xeric scrubs, dry scrub woodlands, humid forests, dry rocky shrub lands, tropical and semi-tropical islands. They make use of different habitats seasonally. Iguanas are more common in humid forests on tropical and semi-tropical islands. During the wet season, vegetation in these areas becomes more abundant and greener. In the dry season, a suitable site is a mixture of gravel and fine sand, bordered by low vegetation; such habitats used in the dry season include xeric scrubs, dry scrub woodlands, and dry rocky shrublands. They are less common in dense forested areas and are more commonly found in boulder-lined hills and patchy vegetation that does not form a complete canopy near open areas. Although no lesser Antillean iguanas have been documented at elevations exceeding 287 m, research suggests they can be found as high as 300 m above sea level. They are more common at lower elevations throughout their range. (Knapp, et al., 2016; van Wagensveld, 2015)

  • Range elevation
    300 (high) m
    984.25 (high) ft
  • Average elevation
    287 m
    941.60 ft

Physical Description

Lesser Antillean iguanas are sexually dimorphic and dichromatic. Females are usually bright green upon hatching and maintain this color through maturity, though in some cases larger females turn grey as they mature. Adult males are green upon hatching and develop a slate grey color as they approach maturity. In comparison with females, males have larger heads and bodies, more pronounced cheeks, and larger dorsal spines. For individuals of both sexes, their jowls, jaws, throats, and snouts become white with age. Both sexes also have singular white spots on the ventral portions of both hind legs. These white spots are pheromone glands, which lesser Antillean iguanas use to communicate. Males have more pronounced pheromone glands compared to females. Males also have internal hemipenes, which are externally visible as two bulges near the base of their tails. Females lack such bulges. Both sexes have pink cheeks, which are most noticeable on males, especially during mating season.

Compared to adults, juveniles are primarily bright emerald green in color. Towards their tails, this bright green changes to a black or brown color. Their extremities and torsos are darker green, which helps them blend in with their surroundings.

Comparing measurements between adult males and female lesser Antillean iguanas, the largest male captured had a snout-vent length (SVL) of 32.9 cm (with typical adult ranges 27 to 28 cm), a total length (TL) of 131.0 cm, and a mass of 2.87 kg. The largest female captured had a SVL of 30.8 cm (with typical adult ranges 24 to 25 cm), a TL of 122.6 cm, and a mass of 2.50 kg. Lesser Antillean iguanas with SVLs below 18.3 cm are considered juveniles. The smallest captured hatchling was reported to have a SVL of 7.6 cm, and a TL of 29.3 cm. The mass for this individual was not recorded.

The genus Iguana includes two species: lesser Antillean iguanas and green iguanas (Iguana iguana). A physical feature that differentiates these two species is the size of their subtympanic plates. Green iguanas have a much larger subtympanic plate than lesser Antillean iguanas. Another distinguishing feature is the large scales on their faces. Lesser Antillean iguanas have broad linear scales on their maxillae, whereas green iguanas have large, scattered scales below their eardrums. Furthermore, green iguanas have lateral black bars along their tails, whereas lesser Antillean iguanas have a slate-grey tail with no lateral bars. (Breuil, 2013; van Wagensveld, 2015)

  • Sexual Dimorphism
  • male larger
  • female more colorful
  • Range mass
    2.87 (high) kg
    6.32 (high) lb
  • Range length
    24 to 131 cm
    9.45 to 51.57 in

Development

Lesser Antillean iguanas exhibit internal fertilization and are oviparous, laying clutches of 4 - 26 eggs (average: 12.5) at a time. The sex of each hatchling is determined during the second trimester, when gonads develop based on the average soil temperature. Although temperatures below 18 °C are lethal, the islands throughout the distribution of lesser Antillean iguanas rarely have ambient temperatures that fall below 24 °C. Hatching often takes several hours to a day for young to completely emerge from the eggs. Although length at hatching has not been reported, the smallest hatchling captured on St. Eustatius Island had a snout-vent length (SVL) of 7.6 cm and a total length (TL) of 29.3 cm.

Lesser Antillean iguana hatchlings with SVLs below 18.3 cm are classified as juveniles. Categorization of adult iguanas was based on the SVL at which they become sexually mature. For each sex, subadult iguanas were categorized at SVLs from 18.3 cm up to length at maturity. Males reach maturity at SVLs of 27 to 28 cm, and females reach maturity at SVLs of 24 to 25 cm. It takes 2 to 3 years for lesser Antillean iguanas to reach adult size. Breeding in smaller, younger males is unlikely because larger, dominant males outcompete them for territories.

Lesser Antillean iguanas exhibit indeterminate growth. They grow about 16.4 cm in their first 2 to 3 years. After reaching maturity, the rate of growth slows. The maximum reported total length was 131 cm for a male and 122.6 cm for a female. ("Lesser Antillean iguana, Iguana delicatissima: Conservation Action Plan", 2014; van Wagensveld, 2015; Zug, 1993)

Reproduction

Little is known about the mating systems of lesser Antillean iguanas. However, green iguanas (Iguana iguana) employ a polygynous system and are closely related to lesser Antillean iguanas. These two species also hybridize, which makes it likely that lesser Antillean iguanas employ the same mating system. Male lesser Antillean iguanas are very territorial and aggressive during mating season, leaving mating marks such as bites and scratches on female iguanas.

Female lesser Antillean iguanas travel alone to communal nesting areas; males are not involved in parental care after the act of mating. Females migrate from inland habitats to find more suitable nesting sites along the coast. A common nesting site on Dominica Island is an exposed coastal slope at a 45-degree angle. It lacks vegetation due to consistent nest excavation by iguanas. Female lesser Antillean iguanas dig mostly in the morning through late afternoon. They build one burrow at a time, which can be up to 1 m long and can take several days to make.

Female lesser Antillean iguanas remain alert when digging. They can become defensive when threatened by other females and are more prone to violence during nesting season. The aggression fades once the eggs have been laid and the opening of the burrow is covered with surrounding substrate. Females typically flee the area if disturbed by potential predators. Once their eggs are hidden, females leave the nest and migrate inland.

Within their home range both female and male lesser Antillean iguanas have hides. Hides are like burrows that they use for protection from predators, to establish territories, and to provide shelter from heat or inclement weather. Because suitable nesting sites for female Lesser Antillean iguanas are rare to find, a study in 2015 deployed 6 artificial nest boxes on St. Eustatius island. However, these boxes were not used by females; the author concluded their deployment methods likely made the boxes not conducive for egg laying. (Frye, 1995; Knapp, et al., 2016; van Wagensveld, 2015)

Lesser Antillean iguanas are iteroparous and they mate during the wet season from April through June. The time between mating to egg-laying is about 6 months. Female lesser Antillean iguanas travel to coastal areas to find suitable substrate for egg burrows. Females select areas that reduce the risk of flooding and have proper levels of solar exposure and moisture levels. Such areas provide the necessary thermal and hydric conditions to ensure that juveniles hatch successfully. A study on the island of Dominica in 2016 found that lesser Antillean iguanas lay clutches with an average of 12.5 eggs (range: 4 to 26 eggs). Eggs had an average mass of 19.6 g (range: 10.0 to 23.7 g), an average length of 45.3 mm (range: 31.3 to 51.8 mm), and an average width of 29.5 mm (range: 24.0 to 34.5 mm).

The incubation period for lesser Antillean iguana eggs lasts approximately 3 months. Birth mass and gestation period have not been reported. Lesser Antillean iguana hatchlings usually emerge from their burrows between August and September. For 1 to 2 years after hatching, juveniles stay huddled together to avoid predation as they forage for food and shelter. Although hatchling masses and lengths have not been reported, both male and female iguanas reach sexual maturity after 5 to 6 years. Males are considered mature adults when they reach a snout-vent length (SVL) of 27 to 28 cm. Females are considered mature at a SVL of 24 to 25 cm. (Knapp, et al., 2016)

  • Breeding interval
    Lesser Antillean iguanas delicatissima breed once a year usually in the wet season.
  • Breeding season
    April-June
  • Range number of offspring
    4 to 26
  • Average time to independence
    0 days
  • Average age at sexual or reproductive maturity (female)
    5 years
  • Average age at sexual or reproductive maturity (male)
    6 years

Male lesser Antillean iguanas show no parental investment beyond the act of mating. Female iguanas show pre-laying parental investment. They travel from inland habitats to coastal areas to find proper nesting sites that ensure high hatching success rates. The migrations that females make are energetically expensive and dangerous. Not only are females more exposed to predation during these trips, but they also frequently cross roads and thus are exposed to higher rates of car-related mortality. Female lesser Antillean iguanas exhibit no further parental investment beyond the act of burrow construction in suitable habitats. Lesser Antillean iguanas are independent at birth. (Knapp, et al., 2016)

  • Parental Investment
  • no parental involvement
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

There is little information on the typical lifespan of lesser Antillean iguanas, but such data does exist for a close relative, common green iguanas (Iguana iguana). Common green iguanas are reported to live 19.8 years in captivity. One study attempting to document lifespans for lesser Antillean iguanas in captivity reported a maximum of 4 years and 5 months. However, this individual was taken from the wild as an adult and kept in captivity. Therefore, this instance should be considered a minimum expected lifespan for lesser Antillean iguanas in captivity.

Although longevity studies have not yet been conducted for wild lesser Antillean iguanas, multiple authors have speculated that these iguanas could reach 25 years of age. Mortality rates likely vary based on age and sex. A study in 2016 reported that 102 iguanas were killed on roads. Of the 72 iguanas that could be identified by sex or age, 60 were females, 10 were males, and 2 were hatchlings. At least 57% of the females in this study were heading to or departing from nesting sites. (Knapp, et al., 2016; Slavens and Slavens, 2018)

  • Typical lifespan
    Status: captivity
    53 (low) months

Behavior

Lesser Antillean iguanas are mostly solitary animals that congregate for mating purposes. They are scansorial and terricolous, spending most of their time in trees or on the ground, either basking or foraging for food. Lesser Antillean iguanas are diurnal and are active from the early morning into the mid to late evening.

Males are more territorial than females. Males fiercely defend their territory against other male iguanas when there are limited food resources or if an area is densely populated. Male lesser Antillean iguanas are often accompanied by the same individual females within their territory, and males and females often bask together. Females only show aggression towards predators or towards other females during egg-laying season. Males and females create their own private hides or burrows and are generally sedentary. They stray no more than 25 to 30 m away from their hides while foraging or basking.

Female iguanas migrate round trip from inland habitats to coastal areas, where they lay eggs. The average round-trip distance traveled by females on the island of Dominica was estimated to be 1,248 m (range: 45 to 4,070 m). Because females travel such long distances, they are more vulnerable to vehicular collisions compared to males. (Knapp, et al., 2016; van Wagensveld, 2015)

Home Range

Home range size had not been estimated for lesser Antillean iguanas. Although males defend territories, exact territory sizes have not yet been quantified. (van Wagensveld, 2015)

Communication and Perception

Lesser Antillean iguanas have a variety of communication methods depending on the situation. Male lesser Antillean iguanas communicate by leaving pheromone trails during mating season. They also leave pheromone trails to mark territories.

Iguanas use their external sense organs to perceive their surrounding environment. The external sense organs are used to detect and escape from predators. Internal sense organs are involved in the timing of development and maturation. Iguanas use their tympanums, or eardrums, to detect sound and other vibrations in their environment. Their tympanums are flush with their heads and can be seen from a lateral view. They are located above their ear shields, behind each of their eyes.

Lesser Antillean iguanas can perceive shapes, shadows, colors, and far away movement. Iguanas use visual signals to communicate with other iguanas.

Lesser Antillean iguanas have a single parietal eye, located on the dorsomedial portion of their heads. This organ is sensitive to changes in light. It is important in determining circadian rhythm and hormone regulation associated with thermoregulation and reproduction. (Lazell Jr, 1973; Wada, et al., 2012; Zug, 1993)

Food Habits

Lesser Antillean iguanas are herbivorous and consume a wide variety of plants, fruits, and seeds. They are known to consume Manchineel (Hippomane mancinella), a tree species that produces chemicals that are toxic to mammals and birds. Lesser Antillean iguanas are the largest native herbivores on St. Eustatius Island. During the wet season (August to December) they consume leaves from various plants and also eat fruits from multiple plant species, including Barbados cherry (Malpighia emarginata) and Manchineel (Hippomane mancinella). During the dry season (January to May), lesser Antillean iguanas tend to consume more foliage than fruit. Adult males and females share the same food habits. Lesser Antillean iguanas commonly consume fruits from chink bush (Bourreria succulenta).

Lesser Antillean iguanas forage most actively around 1100 h (range: 1030 h to 1300 h). Juveniles consume fruit from gray nicker (Guilandina bonduc), and leaves from sugar apple (Annona squamosa). ("Conservation of the Lesser Antillean iguana, Iguana delicatissima, on Anguilla", 1998; van Wagensveld, 2015)

  • Plant Foods
  • leaves
  • fruit

Predation

Known predators of Lesser Antillean iguanas include feral cats (Felis catus) and dogs (Canis lupus familiaris), which kill both hatchlings and adult iguanas. A study from 2018 reported that the presence of cats on St. Eustatius Island has directly led to lower hatchling survival rate. Additional predators of Lesser Antillean iguanas include red-tailed hawks (Buteo jamaicensis) and American kestrels (Falco sparverius). Juveniles also serve as prey items for red-bellied racers (Alsophis rufiventris) and Dominican ground lizards (Ameiva fuscata). Humans (Homo sapiens) hunt Lesser Antillean iguanas for money or sport. On St. Eustatius Island, hunting of lesser Antillean iguanas recently increased due to an economic decline following hurricanes in 2017. Iguanas have cryptic coloration, which helps them blend into their environment and avoid predation. If lesser Antillean iguanas are under threat, they can also drop their tails, which continue to move around and can distract pursuing predators. Lesser Antillean iguanas are able to regenerate their tails if they drop them. (Knapp, et al., 2016; van den Burg, et al., 2018; van Wagensveld, 2015)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Lesser Antillean iguanas are herbivorous that eat leaves, fruits, and seeds of several plant species. They are capable of consuming Manchineel (Hippomane mancinella), which is toxic to mammals and birds. Common predators of these iguanas include cats (Felis catus), dogs (Canis lupus familiaris), humans (Homo sapiens), birds, snakes, and other lizard species. A total of 517 lesser Antillean iguanas on the island of Dominica were surveyed for ectoparasites, and one species of tick (Amblyommma antillorum) was documented on 100% of surveyed individuals. Lesser Antillean iguanas also serve as hosts for the internal parasite (Plasmodium carinii). (Durden, et al., 2015; Knapp, et al., 2016; Thompson and Huff, 1944; van den Burg, et al., 2018; van Wagensveld, 2015)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Ecotourism is growing with tourism in Caribbean countries. With the increase in tourism, Galápagos National Park was able to generate more than $5 million. Of this income, 40% went into hiring more employees, updating the park, and purchasing electronic equipment. Another 40% went towards funding local towns, councils, and authorities. The last 20% went to quarantine programs, the Navy, the Marine Reserve, and other National Parks. Lesser Antillean iguanas are a potential source of ecotourism and inhabit Caribbean islands such as Dominica, where there has been a recent uptick in visitors. The total number of visitors to Dominica has increased from 45,087 in 1990 to 60,417 in 1995.

Lesser Antillean iguanas have historically been used as a source of food, which may have an economic impact on island communities. (Knapp, 2004)

Economic Importance for Humans: Negative

There are no known adverse economic effects of lesser Antillean iguanas on humans.

Conservation Status

Lesser Antillean iguanas are listed as a species that is "Critically Endangered" on the IUCN Red List and is listed under Appendix II on CITES. Animals placed under Appendix II have to be authorized for international trade and granted an export permit. They have no special status on the U.S. federal list and the state of Michigan list.

The greatest threat to lesser Antillean iguanas is hybridization with common green iguanas (Iguana iguana). Hybridization between these two species has caused a rapid decline in populations of Lesser Antillean iguanas. According to a study from 2015, the last genetically pure populations of Lesser Antillean iguanas are restricted to the islands of St. Barthhélemy, Dominica, La Désirade, La Petite Terre, and St. Eustatius.

Countries in the Caribbean are making a conservation effort and have a minimum of 45 National Parks, and at least 164 protected areas for lesser Antillean iguanas. Hunting is usually prohibited, but such policies are not always strictly enforced by local authorities. (Knapp, 2004; "Lesser Antillean iguana, Iguana delicatissima: Conservation Action Plan", 2014; Powell, 2004; van Wagensveld, 2015)

Contributors

Elena Hall (author), Radford University, Sierra Felty (editor), Radford University, Bianca Plowman (editor), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

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