Journal of Herpetology

Boa constrictor was first documented on the island of Aruba in April of 1999. By the end of December, 2003, 273 B. constrictor had been captured. These snakes ranged in size from neonates (0.30 m total length) to large adults (2.8 m total length) and included at least two gravid females. Boa constrictor is currently distributed islandwide with the highest frequency of occurrence in the southern and southeastern portions of the island. The increasing frequency of occurrence, extensive distribution, and size diversity of B. constrictor indicate that a large, reproductively successful population is established on Aruba. The diet of the B. constrictor on Aruba was determined from the examination of stomach content and scat samples (N = 47). Birds comprised 40.4%, lizards 34.6% and mammals 25.0% of 52 separate prey items identified. A correlation was found between snake total length and prey mass (r(28) = 0.49, P < 0.01) suggesting an ontogenetic shift in the diet at a total length of approximately 1.0 m. In view of the diverse diet and increasing population of B. constrictor, there is concern about the potential impact of this invasive predator on the Aruban fauna. A government instituted euthanization program for all captured B. constrictor has proven ineffective at controlling the population.

The island of Aruba is home to several endemic species, and has been colonized recently by the invasive boa, Boa constrictor. We present data for a multiple-year sampling effort on one of Aruba's endemic species, the Aruban Whiptail Lizard (Cnemidophorus arubensis). Our sampling began before the invasion of B. constrictor and ended after their firm establishment, thus affording us the unique opportunity to document the potential effects of this invasive snake on the endemic lizard. Additionally, we compare our data with earlier studies with an average lizard density of 235.1/ha (SE = 73.42, n = 11). After the invasion of the B. constrictor we calculated densities of C. arubensis as high as 2,185/ha. Although B. constrictor regularly preys upon C. arubensis, the relationship between B. constrictor and C. arubensis likely represents ecological facilitation of the lizard species. Herein, we further develop a hypothesis that may explain how the invasive B. constrictor has caused an increase in the population of this endemic lizard. Additionally, we suggest and discuss a few alternative hypotheses that may also account for this observed pattern of increased density. This study identifies a need for continued monitoring of Aruba's native fauna, as well as the need for further experimental approaches to understand the mechanism by which invasive predators ecologically interact with native prey.

ABSTRACT

We used nightly surveys to monitor the status of building-dwelling gecko species on the southern Caribbean island, Curac ̧ ao. Two gecko species were detected in 10 counts across five nights from 18 sites. We recorded the nonnative Wood Slave, Hemidactylus mabouia (81%, 369/455 observations), native Dutch Leaf-Toed Gecko, Phyllodactylus martini (11%, 50/455 observations), and unidentified geckos (8%, 36/455 observations) on the island. The Dutch Leaf-Toed Gecko was most common near the forest and rare elsewhere. Wood Slave abundance was not influenced by forest proximity. Wood Slaves commonly perched near lights that provided heat and attracted insect prey. In contrast, the Dutch Leaf-Toed Gecko perched away from lights. Similar to gecko species in Florida, Wood Slaves displaced Dutch Leaf-Toed Geckos. The Dutch Leaf-Toed Gecko was syntopic with the Wood Slave on buildings near the forest when resources were not limiting or if other gecko populations were not self-sustaining. As Wood Slave populations grew, they excluded Dutch Leaf-Toed Geckos, and possibly Antilles Geckos, Gonatodes antillensis, from these buildings. This exclusion adds novel obstacles to the continued survival of the Dutch Leaf-Toed Gecko on Curac ̧ ao. A similar situation may be present on Bonaire, and for a congeneric species on Aruba, where the Wood Slave is a more-recent colonist. 

Boa constrictor was first documented on the Caribbean island of Aruba in 1999. Despite intensive efforts to eradicate the snake from the island, B. constrictor has established a stable, reproductively successful population on Aruba. We generated mitochondrial sequence and multilocus microsatellite data for individuals from this population to characterize the origins and means of introduction to the island. Phylogenetic analyses and measures of genetic diversity for this population were compared with those for invasive B. constrictor imperator from Cozumel and B. constrictor constrictor from Puerto Rico. Cozumel populations of B. c. imperator had significantly higher number of alleles and significantly higher values for FIS than the Puerto Rico and Aruba populations. Observed, expected, and Nei's unbiased heterozygosities, as well as effective number of alleles, were not significantly different. The effective population sizes from Aruba and Puerto Rico were generally lower than those for either of the Cozumel populations; however, there were broad confidence intervals associated with published estimates. We conclude that the present B. constrictor population on Aruba probably was not established from the introduction of a single gravid or parthenogenic female but instead most likely resulted from the release or escape of a small number of unrelated captive snakes. This study adds to the growing body of evidence suggesting the ease with which a small number of relatively slow-maturing B. constrictor can quickly invade, become established, and avoid eradication efforts in a new location with suitable habitat.