25 May Saban iguana put on the map Saba News

25-MAY-2022 – A unique but virtually unknown black iguana population occurs on Saba on the Dutch Caribbean islands. Due to the many threats on islands worldwide, including the Lesser Antilles and Saba, fieldwork was carried out in 2021 to map this unique population and to indicate the threats it faces.

As on St. Eustatius, the most urgent threats on Saba also seem to be the low growth of young iguanas, the limited amount of suitable nesting sites and the presence of non-indigenous iguanas.

Precise taxonomic status under discussion
The iguana population on Saba is part of the recently described species Iguana melanoderma . While the iguanas’ unique appearance is undisputed, experts are still debating their precise taxonomic status. Despite that discussion, it is clear that protecting the population is urgent, given the number of threats that the population is facing. The main concern is the presence and possible further influx of non-native iguanas from neighboring Sint Maarten.

25 May Saban Iguana put on the map Saba News

Fortunately more iguanas than expected
A recent study estimated the iguana population at only two hundred to three hundred adults. This number is extremely worrying and would seriously threaten the long-term survival of the population. Because the data used in that initial estimate was only preparatory, a new fieldwork project was carried out on Saba in 2021. During this period, 38 transects were monitored several times. This allowed statistical methods to be applied to estimate population size more accurately. An unexpected positive result is that the population is at least a factor of ten larger than previously thought, and therefore concerns several thousand animals.

Large group of adult iguanas rest in the sun for their thermoregulation
Large group of adult iguanas rest in the sun for their thermoregulation (Source: Thijs van den Burg)

The higher the more melanism?
Black (or melanistic ) reptiles are usually believed to have adapted their color to cold environments so that they can warm themselves more quickly; after all, they are cold-blooded . This could possibly also apply to the iguanas of Saba. There is the highest mountain in the Dutch Kingdom, the volcano called Mt. Scenery (887 meters). This high volcano means that Saba is often in the clouds, making it difficult for reptiles to warm up. However, we found no relationship between the degree of melanism and the height at which the iguanas occur. Iguanas that live higher on the mountain are therefore no darker than iguanas that live at lower altitudes.

25 May Saban Iguana put on the map Saba News

Is there another explanation why the iguanas on Saba are black? Another hypothesis would be that the original iguanas that settled on Saba were already black. This is consistent with the occurrence of partially black iguanas in Venezuela, which appear to be genetically closely related to the iguanas of Saba.

Few nesting sites and juvenile iguanas
High quality nesting sites are essential for successful reproduction and maintenance of an iguana population. Goats are known to destroy iguanas’ nesting sites through overgrazing, leading to habitat degradation. Goats can also destroy a nest by their step. This causes the nest to collapse and the embryos to die.

25 May Saban Iguana put on the map Saba News

There is a large (several thousand animals) goat population on Saba that strongly influences the vegetation of the island and causes erosion. During the research, nesting sites were therefore also sought in order to map the availability, distribution and quality. Despite not being the main aim of the study, the findings are regrettable, with only four nesting sites identified.

Juvenile iguana on Saba
Juvenile iguana on Saba (Source: Thijs van den Burg)

An additional concern is the low number of juvenile iguanas found during fieldwork. Of the more than 600 individuals observed, only 2.4 percent were juvenile or younger. Although the exact cause of this is unknown, the feral cat population is one possible cause. Previous research on Saba has shown that the cats mainly live in the lower parts of the island, where they can hunt better. This is also exactly where the iguanas prefer to nest. Iguana remains were also found in no less than nine percent of the cat droppings studied.

This makes the situation for the iguana on Saba similar to that for the Antillean iguana on St. Eustatius, where the presence of cats and goats and the lack of nesting sites are known problems. Targeted research and management measures are urgently needed on both islands.

25 May Saban Iguana put on the map Saba News

Continued Concerns
Despite the larger than expected iguana population on Saba, there are therefore several reasons for concern. The need for better protection and the continuation of knowledge gathering is evident. Main concerns for the survival of the species are the presence of stray cats and goats, the low number of juvenile iguanas and low availability of nesting sites. By far the greatest threat, however, comes from the presence of non-native iguanas, which can mix with and suppress the native population through competitive hybridization. During the fieldwork, animals have been seen that are completely different from the native animals and preliminary genetic research has already shown that these animals are indeed not native.

Population estimate, natural history and conservation of the melanistic Iguana Iguana population on Saba, Caribbean Netherlands

Intraspecific diversity is among the most important biological variables, although still poorly understood for most species. Iguana iguana is a Neotropical lizard known from Central and South America, including from numerous Caribbean islands. Despite the presence of native melanistic I. iguana populations in the Lesser Antilles, these have received surprisingly little research attention. Here we assessed population size, distribution, degree of melanism, and additional morphological and natural history characteristics for the melanistic iguanas of Saba, Caribbean Netherlands based on a one-month fieldwork visit.

Using Distance sampling from a 38-transect dataset we estimate the population size at 8233 ±2205 iguanas. Iguanas mainly occurred on the southern and eastern sides of the island, between 180-390 m (max altitude 530 m), with highest densities both in residential and certain natural areas. Historically, iguanas were relatively more common at higher altitudes, probably due to more extensive forest clearing for agricultural reasons.

25 May Saban Iguana put on the map Saba News

No relationship was found between the degree of melanism and elevation, and few animals were completely melanistic. Furthermore, we found that body-ratio data collection through photographs is biased and requires physical measuring instead. Although the population size appears larger than previously surmised, the limited nesting sites and extremely low presence of juvenile and hatchling iguanas (2.4%), is similarly worrying as the situation for I. delicatissima on neighboring St. Eustatius.

The island’s feral cat and large goat population are suspected to impact nest site quality, nest success, and hatchling survival. These aspects require urgent future research to guide necessary conservation management.

25 May Saban Iguana put on the map Saba News

https://www.hurricanecaribbean.wordpress.com
https://hurricanecaribbean.blogspot.com/
http://stmaartennews.org/
https://sxmpolitico.wordpress.com/
https://sxmprosecutors.wordpress.com/
https://judithroumou.wordpress.com/
https://stmaarten.news/
https://caribbeannewsnetwork.wordpress.com/
https://discoverstmaarten.wordpress.com/
https://melissagumbs.family.blog/
https://onderzoeksintmaarten.wordpress.com/
https://pjd2caribbeanqueenpageant.wordpress.com/
https://nardycramm.wordpress.com/
https://sxmgovernment.com/
https://susanthompsonwrinkledracistdemon.art.blog/
https://sxm777.wordpress.com/
https://stmaartencarnival.wordpress.com/
https://sxmcarnivalthebest.wordpress.com/
https://sxmdungeon.wordpress.com/
https://sxmgovernmenthookers.politics.blog/
https://sxmmelee.wordpress.com/
https://sxmpolice.wordpress.com/
https://sxmpolice2.wordpress.com/
https://sxmbumbablogs.wordpress.com/
https://terrancereycocksoup.wordpress.com/
http://stmaartennews.org/
https://www.hurricanecaribbean.wordpress.com

25 May Saban Iguana put on the map Saba News