A glimpse of Statia's nature
Facts - the Lesser Antillean Iguana

The Lesser Antillean Iguana is a species of iguana that is endemic to the Caribbean. Historically, Iguana delicatissima is believed to have existed throughout the northern Lesser Antilles, from Anguilla to Martinique. The species has experienced dramatic declines since European contact, causing the extirpation of some populations and the severe decline of others.

This means the Lesser Antillean Iguana has since been extirpated from Saint-Martin (French and Dutch sides), Antigua, Barbuda, St. Kitts, Nevis, and Marie-Galante. Ongoing surveys conducted on Guadeloupe since 2007 suggest that populations have been extirpated from Grande-Terre and Les Îles des Saintes islets. However, individuals are still present along with Green Iguanas (Iguana iguana) and hybrids on Basse-Terre, but biologically viable populations are most likely extirpated. Based on the historical range data, the total population of the Lesser Antillean Iguana has most likely experienced declines of more than 70% since European contact.

Once thought to be present in large numbers on St. Eustatius before European colonization, the population is rapidly declining. Past populations size estimates were about 300 animals in 1992, less than 300 individuals in 2000, and about 425 (275-650) individuals in 2004. A recent population update now estimated to be just a few hundred, and population densities have declined across all habitats on the island since the last assessment in 2004 (Debrot et al. 2013). This is far below the required minimum viable population size of 5,000 animals and means that the Lesser Antillean Iguana is critically endangered on St. Eustatius.

 
Conservation issues

Habitat loss and fragmentation were historically most extensive on the least mountainous areas, which were systematically cleared for agriculture. As tourism and other economic growth superseded agriculture in importance, (coastal) development has further reduced the remaining habitat and significantly affected already-limited communal nest-sites (Day et al. 2000). Road casualties occur regularly along coastal road, which bisect iguana habitat.

Lesser Antillean Iguanas are impacted by a range of introduced predators. Predation by both cats and dogs is a large problem. Adult iguanas are known to be killed by guard dogs that run free within fenced properties where iguanas move to feed.

Free-ranging and feral browsing competitors are present on St. Eustatius. Goat and cow populations are particular large and of most concern. Extensively overbrowsing continues to cause a shift in plant species composition and habitat structure. Another threat is the ongoing degradation of natural vegetation attributable to the spread of invasive alien species, most notably the Mexican Creeper (Antigonon sp.), which is unpalatable to both goats and iguanas (Fogarty et al. 2004; Debrot et al. 2013).

Hunting is likely a minor problem, primarily because population densities are so low that it is not worth the effort. Other notable sources of iguana mortalities are starvation (or drowning) in abandoned cisterns and entanglement in fencing.

Displacement through competition and hybridization with the common Green Iguana (Iguana iguana) appears to be the dominant factor in the disappearance of the Lesser Antillean Iguanas in the region. This proces is rapid and subsequent population extirpations have been recorded from several islands in the French West Indies. Sadly a single green iguana female was discovered in early 2016, along with another 6 hybrid iguanas on St. Eustatius since.  Hybridization is now considered the main threat for the lesser antillean iguanas existance throughout its natural range. The introduction of green iguanas and hybrids has to be prevented at all costs!

Overview

Documented death or endangerment of iguanas in St. Eustatius, April-December 2012 (source: Debrot et al. 2014, Herpetological Review 45(1), p129)

Dogs: 10 death, 1 rescue
Traffic: 3 death, 0 rescue
Cistern: 1 death, 4 rescue
Fencing: 0 death, 6 rescue
Hunting: 2 death, 0 rescue
Unknown: 1 death, 0 rescue

Total incidents of 28 individuals in 2012.






Notice the differences

Iguanas in the Lesser Antilles include only two species of the genus Iguana. The common Green Iguana (Iguana iguana) and the Lesser Antillean Iguana (Iguana delicatissima). For the untrained eye I. iguana and I. delicatissima look quite similar but can be most easily distinguished by the large subtympanic scale that can be found under the jaw on the cheeks and the unmistakable black and green banding of the tail, both typical features of the Green Iguana. Other key features to distinguish the two species are:

  • The common Green Iguana has bands on its tail, whereas the Lesser Antillean Iguana has not.
  • The Lesser Antillean Iguana also has a large number of small scales instead of a single plate below its ear.
  • As the Lesser Antillean Iguana ages, the color of its skin will change from green to a slate grey color, although females sometimes retain some of the green body color.
  • The Lesser Antillean Iguana is also slightly smaller than the common Green Iguana.
  • Reproductively active Lesser Antillean Iguana males and even some females develop distinctly pink cheeks.
  • Skull morphology (Conrad and Norell 2010) and more than 15 morphological characters (Breuil 2013).

Left: juvenile Iguana iguana. Right: juvenile Iguana delicatissima (photo by Gregory Moulard)