The Lesser Antillean Iguana (Iguana delicatissima) was once found throughout the Lesser Antilles, ranging from Anguilla to Martinique, but population sizes have been subject to a rapid decline. Nowadays, the Lesser Antillean Iguana is found on only 13 islands in the region, with St. Eustatius being its last refuge within the Dutch Caribbean, hence its listing on the IUCN Red List as an Endangered Species facing extinction. Of these 13 island populations, only two exceed the long-term minimum viable population size of 5,000 individuals (Dominica and Guadeloupe) and on six the species is on the brink of extinction.
Until recently, St. Maarten was also home to a population of this bright-green miniature dragon, but due to the introduction of the Green Iguana (Iguana iguana) in the mid-90s, that population has seized to exist. The larger and more aggressive Green Iguana not only out-competes its smaller relative, but because the species are so closely related genetically, they can interbreed creating “hybrid” species. This forms a major threat to preserving the integrity of the species.
The Green Iguana (left) and the Lesser Antillean Iguana (right) can most easily be distinguished by the large sub-tympanic 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.
On St. Eustatius, to date the Green Iguana has not been introduced, making St. Eustatius home to one of the last surviving, potentially viable and genetically pure populations of the Lesser Antillean Iguana, which emphasises the international responsibility we have to conserve this endangered reptile.
Population sizes for the Lesser Antillean Iguana on St. Eustatius have been estimated in the past at around a few hundred individuals, which is already far below the minimum viable population size. Earlier in 2013 it became clear that since 2004, population densities have declined to an average of 0.35 iguanas per square hectare across all habitats on the island, which is less than 1% of the average densities of healthy populations documented elsewhere and certain populations on St. Eustatius have even disappeared completely.
Even though on St. Eustatius hunting by humans seems to be minor, shelter and food availability on the island are abundant, invasive predator densities in the wild are relatively low and the Green Iguana is not (yet) present, the population has declined nonetheless. The cause for this is the limited availability on St. Eustatius of un-lit, barren, sandy and well-drained nesting sites, a prerequisite for the Lesser Antillean Iguana.
Additionally, a lot of iguanas are killed or injured by getting entangled or trapped in fences around gardens and/or molested by dogs. So it seems that the lack of nesting sites and high iguana mortalities due to anthropogenic causes are the two main factors limiting recovery of the Lesser Antillean Iguana on St. Eustatius.
To counter this negative trend, a few measures could be implemented for better protection of the wild population of Lesser Antillean Iguanas on St. Eustatius. To start with, customs officials should be trained to prevent potential entry of the mongoose and the Green Iguana from neighbouring islands. Improved enforcement and updated protective legislation will create a supportive legal framework for protection. Furthermore, the development and maintenance of new nesting habitat, a measure that is both easy and inexpensive, and the establishment of a programme to promote “iguana-friendly” gardens can alleviate pressure off the two greatest threats for the Lesser Antillean Iguana on St. Eustatius.
Additionally, an on-island husbandry and breeding project could potentially play a crucial role in the survival of the Lesser Antillean Iguana and would increase public awareness for the current status of the species by providing a relaxed setting in which the local community can experience the iguana as the gentle and beautiful animal that it is.
Sources: – Debrot, A.O.; Boman, E. K. (2013) The Lesser Antillean Iguana on St. Eustatius: 2012 status update and review of limiting factors. Den Helder: IMARES Wageningen UR, (Report C166/12) – p. 45. – Debrot, A.O.; Boman, E.K.; Madden, H. (2013) The Lesser Antillean Iguana on St. Eustatius: A 2012 population status update and cause for concern. Reptiles and Amphibians 20(2):44–52.