Population estimate, natural history and conservation of the melanisticIguana Iguanapopulation on Saba, Caribbean Netherlands

Abstract

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. 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.

Forensic Genetic Analyses of Melanistic Iguanas Highlight the Need to Monitor the Iguanid Trade

“…Further supporting evidence that the traded iguanas do not originate from Montserrat, St. Croix, or St. Thomas but from Saba is suggested by their strong melanistic appearance. Across these islands, all native iguanas are (partially) melanistic, with at least a distinct melanistic patch between the tympanum and eye [ 15 , 18 , 22 ]. However, body melanism differs considerably between islands, and phenotypes with extensive body melanism equal to that of the traded iguanas appear to only be present on Saba [ 15 , 18 , 22 ].…”

“…Across these islands, all native iguanas are (partially) melanistic, with at least a distinct melanistic patch between the tympanum and eye [ 15 , 18 , 22 ]. However, body melanism differs considerably between islands, and phenotypes with extensive body melanism equal to that of the traded iguanas appear to only be present on Saba [ 15 , 18 , 22 ]. The CITES Trade Database for 2020 indicates that no iguanas were exported from Barbados that year, whereas 390 iguanas, of which 320 were captive bred in origin, were exported from St. Maarten to the USA, Japan, Germany, and the Republic of Korea [ 46 ].…”

“…Despite its ‘least concern’ assignment, regional assessments across I. iguana indicate that local populations can be threatened due to a range of factors. Whereas mainland populations are also locally endangered [ 19 , 20 ], the most at-risk are insular populations in the Lesser Antilles, given a range of prominent threats, e.g., hunting, invasive species, and the spread of non-native iguanas [ 12 , 14 , 15 , 21 , 22 ]. Overall, I. iguana are among the most traded reptiles globally [ 23 , 24 ], with native populations being harvested for trade, often without restrictions [ 20 , 25 ].…”

The complete mitochondrial genome of the Critically Endangered Saba Green Iguana, Iguana iguana (Squamata: Iguanidae)

“… 1997 ) during a population assessment on Saba, Caribbean Netherlands (van den Burg et al. 2022 ). This sample is at the Museo Nacional de Ciencias Naturales (Madrid, Spain; https://www.mncn.csic.es/es , lab of D. R. Vieites, vieites@mncn.csic.es ), under the number SAB01.…”

“…The Saba Green Iguana is a subpopulation of Iguana iguana iguana (Linnaeus 1758), found only on the island of Saba in the Caribbean Lesser Antilles. It has been assessed as Critically Endangered by the International Union for Conservation of Nature (van den Burg and Debrot 2022 ). Like most other Iguana populations in the region, its survival is threatened by the recent arrival of non-native iguanas ( I. iguana ) and the resulting competitive hybridization (van den Burg et al.…”