Reinert, H.K.

Invasive Boa Constrictors (Boa constrictor) have established a reproductive population on Aruba. High

B. constrictor densities could stress prey populations on this small, faunally simplistic island. We examined diet,

size, and condition of 501 B. constrictor at three periods over nearly 15 y: during early invasion, approaching the

peak in encounters, and after 5 y of declining encounters. The 401 prey identified consisted of 32.9% mammals,

37.4% lizards, and 29.7% birds. Dietary proportion of these categories was consistent across sampling periods.

Non-native prey were consumed in relatively high proportions. Despite a positive relationship between snake

snout-vent length and prey mass, even the largest snakes consumed small prey. During the high encounter period,

many snakes had empty digestive tracts, little abdominal fat, and low body mass, possibly due to a decline in prey

availability; however, snakes from residential/agricultural areas had better body condition than those from natural

areas. High population densities of the native Aruban Whiptail Lizard (Cnemidophorus arubensis) may provide a

consistent food supply for B. constrictor in both natural and residential/agricultural areas, and domesticated prey

near human habitation may subsidize the population in residential/agricultural areas. Improved body condition

in the last sampling period suggests that the population is either stabilizing or poised for an increase. The endemic

Aruba Island Rattlesnake (Crotalus durissus unicolor) and B. constrictor had similar, broad diets that overlapped

heavily. Eradication of B. constrictor from Aruba is unlikely, but integration may be possible if the population

can be stabilized at low densities. We recommend continued control efforts and systematic monitoring of prey

populations.

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.

Established in 1982, the Aruba Island rattlesnake Crotalus unicolor Species Survival Plan (SSP) is the longest continual functioning snake conservation effort of the Association of Zoos & Aquariums (AZA). The captive population has been maintained as an assurance population for the most threatened snake on Aruba. Over the last 26 years, 27 potential founders were imported for assimilation into the SSP to maintain genetic diversity. By 2014, the gene diversity in the captive population was over 94%. In 1986, the SSP began working in partner- ship with Arubans to aid the conservation of the rattle- snake and its ecosystem on the Island. This in situ programme has included ecological research, training, management recommendations, capacity building, workshops, public relations and education. These efforts have been integrated into a holistic long-term project that has resulted in many significant conservation suc- cesses. The extensive efforts made by the AZA and SSP to ensure the continued survival of C. unicolor are a model for zoo-based conservation efforts involving reptiles. 

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.