Antillean iguana


donated by Herpetofauna


Within the Dutch Caribbean, the Antillean iguana (Iguana delicatissima) is only found on St. Eustatius, an island of 21 km2. The species is under great pressure from multiple threats, including habitat loss and human consumption, but especially from hybridization with the green iguana (Iguana iguana).

Both terrestrial national parks present on St. Eustatius are home to very few iguanas. The majority of the iguana population therefore lives in unprotected areas. Since 2015, much effort has been directed to understand the distribution and size of the Antillean iguana population. Ahead of the 2017 hurricane season, stakeholders had collectively built an island-wide database of iguana presence (not absence). However, the severity of the 2017 hurricane season, when hurricanes Irma and Maria passed the island, caused the population to decrease by about 25%; which was estimated to be 800-1000 animals prior to the 2017 season. Continuous monitoring of the island is necessary to understand trends in population size, as well as local presence.

Although here have been plans to initiate a “head-starting program”, in which hatchling iguanas are raised to increase their chances of survival, this has not been materialized so far.

Indeed, as the greatest current threat to I. delicatissima remains hybridization with the green iguana, high costs associated with a head-starting program could be used more effective for other initiatives through which the iguana population can be safeguarded. As offspring between the native Antillean iguana and non-native green iguana are fertile and become larger in total size, hybrid offspring has a competitive advantage over the native iguanas. This has and is leading to the decline and eventual disappearance of the Antillean iguana across the entire Lesser Antillean region.

Since 2013, at least four non-native iguanas arrived by boat on St. Eustatius, which presumably all originated from the neighboring island of St. Maarten. This has resulted in at least one successful nest of hybrid offspring, and the capture of 10 hybrid iguanas so far. Continuous monitoring is thus also necessary to identify the presence of remaining, and newly arriving, non-native or hybrid iguanas on St. Eustatius. Currently at least one adult non-native iguana is known to be present on St. Eustatius and remains to be captured.