Iguana delicatissima

Abstract

The Lesser Antilles, in the Eastern Caribbean, is inhabited by three Iguana species: the Lesser Antillean iguana Iguana delicatissima, which is endemic to the northernmost islands of the Lesser Antilles, the introduced common iguana from South America, Iguana iguana iguana, represented also by the two newly described endemic subspecies Iguana iguana sanctaluciae from Saint Lucia and Iguana iguana insularis from Saint Vincent and the Grenadines, and Grenada, and the introduced Iguana rhinolopha from Central America. Drawing on both morphological and genetic data, this paper describes the Iguana populations from Saba and Montserrat as a new species, Iguana melanoderma. This species is recognized on the basis of the following combination of characteristics: private microsatellite alleles, unique mitochondrial ND4 haplotypes, a distinctive black spot between the eye and tympanum, a dorsal carpet pattern on juveniles and young adults, a darkening of body coloration with aging (except for the anterior part of the snout), a black dewlap, pink on the jowl, the high number of large tubercular nape scales, fewer than ten medium sized–triangular dewlap spikes, high dorsal spikes, and lack of horns on the snout. This new melanistic taxon is threatened by unsustainable harvesting (including for the pet trade) and both competition and hybridization from escaped or released invasive alien iguanas (I. iguana iguana and I. rhinolopha) from South and Central America, respectively. The authors call for action to conserve Iguana melanoderma in Saba and Montserrat and for further research to investigate its relationship to other melanistic iguanas from the Virgin Islands and coastal islands of Venezuela.

Keywords: Conservation Biology, Iguana, Lesser Antilles, microsatellites, mtDNA, new endemic species, phylogeny

A new study by Wageningen Marine Research, St. Eustatius National Parks Foundation and Caribbean Netherlands Science Institute highlights the need for a continuation of the rapid response removal campaign to control the invasive green iguana population. Through displacement and hybridization, the green iguana threatens to wipe out the endemic Lesser Antillean Iguanas of St. Eustatius.  

The Lesser Antillean Iguana, , is an IUCN Red List Critically Endangered species, which has disappeared from most of its habitat, including St. Maarten. This species is endemic to St. Eustatius and is the largest native vertebrate on the island. Its main threat comes from displacement by and hybridization with the invasive species green iguana, Iguana iguana.  In fact, St. Eustatius is one of the last three major islands where this species was (until recently) still free from hybridization.  Biological invasions can create several issues which threaten biodiversity, the environment, agriculture, livelihoods, health, and local culture. 

Photo credit: Philippa King

Rapid Response 

In February of 2016, an adult female green iguana was caught in Princess Estates on St. Eustatius. Green iguanas and their hybrid offspring can be most easily distinguished from the native iguana based on their banded tail and the large scale on their cheek (see figure).  It was unknown how long this individual had been on the island and if she had already laid eggs, potentially introducing additional iguanas to the area. In response, the Ministry of Economic Affairs agreed to fund a limited Rapid Response Removal Campaign (RC) on the island.  

During the RC, three visual surveys were conducted throughout key risk areas.  In total, 409.5 hours were spent over 40 days, resulting in a single detection.  This low detection rate suggested that the RC occurred early in the invasion process and highlighted the need to stay vigilant. Luckily, local publicity via newspaper and radio programs led to a number of publicly reported sightings. Among these reports and opportunistic encounters by park management staff, an additional five green iguanas and their hybrids were captured before the campaign ended in January 2017, and an addition eight have been captures since. 

Research 

As part of the RC, a study was conducted by Wageningen Marine Research, St. Eustatius National Parks Foundation and Caribbean Netherlands Science Institute (CNSI) to learn more about this invasion. In addition to tracking population data during the surveys, they also worked to identify introduction events, points of entry and likely points of origin.  The harbor of St. Maarten was identified as the source of the most recent 2020 introductions, as this harbor serves as a major inter-island transshipment hub within the Lesser Antilles.  This recent study highlights four apparently distinct green iguana introduction events between 2013 and 2020, one of which was likely intentional and three of which were from incidental stowaways arriving on container ships. 

Photo credit: Dolfi Debrot

Moving Forward 

Luckily even four years after the RC the numbers of green iguanas and their hybrids appears to be limited.  This gives researchers hope that it is not too late to stop the invasion before it heavily interbreeds with and thus effectively wipes out the island’s critically endangered Lesser Antillean iguana.  Research alone will not be enough to control this issue. Investment both in finances and in capacity necessary to prevent introduction and spread of these iguanas will be required.  RCs are significantly lower in cost than full invasive species removal projects, so the early detection and active management provides a unique opportunity for the island to eradicate this threat while still possible and affordable.   

Report your sightings 

If you happen to spot a green iguana while on St. Eustatius, you can report it to the local park authority STENAPA (+599 318 2884) or CNSI (+599 318 2040) as well as on https://dutchcaribbean.observation.org. This is a free website and app which allows local citizens to report sightings of important plants and animals. These tools are available in over 40 languages and can be used by biologists and citizens and tourists alike. Species reports by local communities are invaluable for nature conservation efforts to help increase public awareness and overall species protection.  

Read the full report on the Case Study of a Rapid Response Removal Campaign for St. Eustatius on the Dutch Caribbean Biodiversity Database. 

https://www.dcbd.nl/document/st-eustatius-invasive-alien-green-iguana-ca...

Article published in BioNews 47

Although the La Soufrière volcano on St. Vincent saw its latest explosive eruption over a week ago, and the threat level has decreased to Orange, caution is still necessary. Uncertainty for the St. Vincent population therefore remains, as thousands of people had to evacuate their villages and stay elsewhere on the island. Further uncertainty and hardship are caused by the eruptions’ effect on local food and water supplies. Gratefully, in a region where catastrophic weather events are not uncommon, regional organizations and nations quickly mobilized relief efforts to aid Vincentians.

In a letter to the journal Science, biologists from 12 Caribbean organizations, including STENAPA on St. Eustatius, highlight the need to prioritize both humanitarian aid and biosecurity when responding to natural disasters. The authors note how bypassing biosecurity could cause additional long-term harm to both the local ecosystems and the human population. Erik Boman, Director of STENAPA, pointed out that this threat is especially grave on islands. The letter also “urge governments and aiding parties responding to catastrophes to recognize and mitigate potential risks”.

Several of the authors have been involved in invasive species control on Dominica, where during the humanitarian aid campaign that followed the passing of Hurricane Maria in 2017, several non-native species were introduced. The local NGO WildDominique is currently working hard to remove both amphibian and reptile species that established populations there. The green iguana is also a biosecurity issue for local iguana, Iguana delicatissima on St. Eustatius. Although thousands of dollars have already been invested in these eradication efforts, a complete assessment of all species that arrived with the aid supplies still awaits. In the aftermath of natural disasters, when the natural environment is heavily affected and recovering, arriving non-native species will have the opportunity to spread out further and would form a major threat to the isolated and native flora and fauna on the island.

The letter further addresses the need for wide and multi-organizational collaborations to prepare for future large-scale humanitarian aid campaigns, of which each will be unique.

Link to Letter at Science: https://science.sciencemag.org/content/372/6542/581

Article published in BioNews 43

ABSTRACT

Catastrophic events, like hurricanes, bring lethal conditions that can have population-altering effects. The threatened Caribbean dry forest occurs in a region known for its high-intensity hurricane seasons and high species endemism, highlighting the necessity to better understand hurricane impacts as fragmentation and clearing of natural habitat continues. However, such studies remain rare, and for reptiles are mostly restricted to Anolis. Here we used single-season occupancy modeling to infer the impact of the intense 2017 Atlantic hurricane season on the critically endangered Lesser Antillean Iguana, Iguana delicatissima. We surveyed 30 transects across eight habitats on St. Eustatius during 2017-2019, which resulted in 344 individual surveys and 98 iguana observations. Analyses of abundance and site occupancy indicated both measures for 2018 and 2019 were strongly reduced compared to the pre-hurricane 2017 state. Iguanas at higher elevations were affected more profoundly, likely due to higher wind speeds, tree damage and extensive defoliation. Overall, our results indicate a decrease in population estimates (23.3-26.5%) and abundance (22-23.8%) for 2018 and 2019, and a 75% reduction in the number of opportunistic sightings of tagged iguanas between 2017-2018. As only small and isolated I. delicatissima populations remain, our study further demonstrates their vulnerability to stochastic events. Considering the frequency and intensity of hurricanes are projected to increase, our results stress the urgent need for population-increasing conservation actions in order to secure the long-term survival of I. delicatissima throughout its range.

With a lot of threats facing the Lesser Antillean Iguana (Iguana delicatissima) on Sint Eustatius it is important to look at solutions that will work on the long term. Though the situation is different to that of other iguanas, it can be helpful and inspiring to look at conservation efforts done in the favour of other iguana species. Both the similarities and differences to the situation on Sint Eustatius could help in creating a plan that is sustainable for the parties involved and that will help to improve the situation of the Lesser Antillean Iguana on Sint Eustatius. In this case the situations of four different iguana species is specified along with the actions taken, the effects of these actions and a more current description of the situation. The situations compared to the situation of the Lesser Antillean Iguana show a striking similarity in some threats, similar threats crop up in almost all situations. There are some measures taken in most all of the situations, these measures are successful but call for some caution. These are general concerns that should be taken under consideration whenever a conservation plan is written. This doesn’t mean that these measures cannot be taken, it advises caution with these measures.

[Student report]

The Lesser Antillean Iguana (Iguana delicatissima) is native to the Lesser Antilles, a group of islands in the Caribbean Sea. The species is in serious decline, and has been extirpated on islands throughout its geographic range. Therefore I. delicatissima now is classified as endangered on the IUCN red list. A better understanding of these animals can help in effectively protecting them. With little known on the behaviour and distribution of the Lesser Antillean iguana on St. Eustatius, I spent 4 months studying this increasingly rare animal. In the search for iguanas approximately 80-84% of the island of St. Eustatius was investigated. To get an idea of the distribution, total population and biology of iguanas, 286 iguanas in total were caught, which includes work done by Thijs van den Burg. Of these iguanas 195 were beaded and 78 were temporarily marked. Nesting sites, hatchling sightings and the distribution of iguanas has been mapped. These maps illustrate fragmentation of the iguana population on St. Eustatius. We have found that both the Boven-and Quill National Parks have very few iguanas, and thus that the majority of iguanas live outside the park boundaries, which is a major cause for concern. Designating new protected areas might be required in order to save the species on St. Eustatius. Further research is needed on nesting behaviour and hatchling dispersion. Furthermore the beading of iguanas must be continued, and continuously monitored. The culling of feral livestock, placement of artificial nests along with a in situ head starting/ husbandry program is suggested to bolster the current population of iguanas.

Iguana delicatissima sightings on St. Eustatius, supported by RAVON (Reptiles, Amphibians and Fish Research Netherlands),  STENAPA and the MSc theses of Thijs van den Burg (Vrije University Amsterdam) and Tim van Wagensveld (Wageningen University and Research).

See this report for more information on the survey.

This issue of BioNews profiles the research and monitoring efforts for January and February 2013 and highlights a new monthly feature, called ‘Research of the Month,’ which presents a more detailed look at some of the fascinating work underway on our islands. This month’s choice is the Lesser Antillean Iguana on St. Eustatius.

Amongst others, you will find in this second issue:

• overview of research and monitoring
• update on the Dutch Caribbean Biodiversity Database
• St. Eustatius’ Lesser Antillean Iguana: Cause for concern
• overview of reports and publications
• calendar of upcoming events, meetings and workshops

To assess the status and current population densities of the endangered Lesser Antillean Iguana (Iguana delicatissima) on the island of St. Eustatius, we spent more than 80 h searching for iguanas and covered more than 63 km of trails and tracks — but found only 22 iguanas, for an overall average of 3.7 h per iguana. Overall population density was 0.35 iguanas per hectare, which represents 0.5–1.0% of densities documented elsewhere in healthy populations. Population densities have declined across all habitats since the last assessment in 2004. The lack of nesting sites and high iguana mortalities due to anthropogenic causes were the two core factors limiting recovery of iguanas on St. Eustatius.

Our principal recommendations are to:

• (a) Train and equip border officials to prevent potential entry of mongooses and Green Iguanas from neighboring islands;
• (b) implement enforcement and upgrade protective legislation;
• (c) develop and maintain new additional nesting habitat, a measure that is both easy and inexpensive; and
• (d) establish a program to promoto "iguana-friendly" gardens as the main means of reducing cumulative mortality.

Finally, we propose the development of an in situ husbandry and breeding program to help bolster the overall recovery program, a move that would also benefit islanders by offering a relaxed setting in which they could better learn to appreciate this emblematic island species.