The Reptile and Amphibian Fauna of Aruba

R. Andrew Odum¹ and Howard K. Reinert²

 ¹Department of Herpetology, Toledo Zoological Society, Toledo, Ohio 43614, USA

²Department of Biology, The College of New Jersey, Ewing, New Jersey 08628, USA

The reptiles and amphibians are a significant part of the ecological communities of Aruba and have assumed many different niches on the island.  The amphibians are represented by three species (three families), two of which are recent introductions.  The reptiles include 14 established species from eight families, of which two are 20^th century introductions (Cnemidophorus l. lemniscatus and Boa constrictor).  Three species of reptiles, (Cnemidophorus arubensis, Phyllodactylus julieni, and Crotalus unicolor) are endemic to the island.  Four species of sea turtle (two families) are also known to use Aruba for nesting.

Lessons learned in control efforts for invasive snakes, with implications for control of Boa constrictor on Aruba

 Robert N. Reed

 Invasive snakes have the potential to drastically alter ecosystems by consuming native vertebrates, especially on islands with low species richness. At a global scale, intensive control efforts for snakes have focused on a few high-profile species [e.g., Brown Treesnake (Boiga irregularis) on Guam, and Habu (Trimeresurus flavoviridis) on islands in southern Japan]. The issue of invasive snakes has recently gained additional attention, due in large part to a rapidly expanding population of Burmese Pythons (Python molurus) in southern Florida, USA. Boa Constrictors (Boa constrictor) have established on Aruba and have colonized much of the island, leading to fears that they will similarly impact native fauna. The primary tools used for snake detection, control, and interdiction include visual searching, trapping (including attractant traps and intercept traps), detector dogs, barriers, and toxicants. Operationally-effective contraceptives, pheromone-based attractants, and biological controls have not been developed for snakes. I will review known cases of invasive snakes and how they have impacted native ecosystems. I will then discuss the feasibility of implementing various detection and control tools for management of invasive Boa constrictor on Aruba, as well as suggestions for preventing the human-assisted spread of this species to Bonaire and Curaçao.

Welcome to Aruba (Part One): The Biology of Johnstone’s frog, Eleutherodactylus johnstonei

Craig Berg / Billie Harisson

Johnstone’s frog, Eleutherodactylus johnstonei is a recent arrival on Aruba. This frog is a highly invasive species that has spread throughout the Caribbean.  It has also made footholds in Central and South America.  The life history and biology of this frog is discussed.

Welcome to Aruba (Part Two): The history of the dispersal of Johnstone’s frog, Eleutherodactylus johnstonei, implications for Aruba.

Johnstone’s frog, Eleutherodactylus johnstonei is a recent arrival on Aruba. This frog is a highly invasive species that has spread throughout the Caribbean.  It has also made footholds in Central and South America.  The history of its spread and impacts on other islands will be described.  Its possible impacts on Aruba will also be discussed.

SAVING ARUBA’S BIODIVERSITY IS IN THE BATS’ WINGS 

Jafet M. Nassar

Instituto Venezolano de Investigaciones Científicas, Centro de Ecología, Carretera Panamericana, Km. 11, Caracas, Edo. Miranda, Venezuela. (jafet.nassar@gmail.com)

The Peri-Caribbean Arid Belt is an ecoregion highly exposed to habitat deterioration and fragmentation, land cover change, population decline and extinction of the native flora and fauna. As one of the favorite tourist destinies in the Caribbean, Aruba Island is subjected to all these threats. The urgently needed plan to preserve Aruba’s biodiversity must emphasize the conservation of keystone species and vital ecological interactions which help maintain the trophic webs represented in this island. In this presentation I offer scientifically sound evidence supporting the idea that cactus-bat mutualistic interactions present in the ABC islands are fundamental for the maintenance of terrestrial biodiversity. Studies on the reproductive biology of Aruban columnar cacti (Stenocereus griseus, Cereus repandus and Pilosocereus lanuginosus) indicate that these keystone plants rely exclusively on nectar-feeding bats (Leptonycteris curasoae and Glossophaga longirostris) for fruit and seed set. On the other hand, dietary studies based on carbon stable isotope analyses unequivocally indicate that these plants, together with agaves, are the main food sources of nectar-feeding bats associated with arid ecosystems in northern South America. This tight interdependence between bats and columnar cacti has long-term consequences in terms of their regeneration and evolutionary potential in the region. Nectar-feeding bats can move cactus and agave propagules over long distances, even overseas, promoting gene flow, expansion of their geographic distribution and colonization of new places. A unified conservation action plan for Aruba’s flora and fauna will require the preservation of the cactus-bat mutualisms in the Netherlands Antilles and the Paraguaná Peninsula.

Alert species

Gerard van Buurt

The very first inhabitants of Aruba, the Archaic Indians and later the Amerindian Caquetío tribe, already started to introduce new species on the island. During colonial times this process was accelerated and nowadays as a result of globalization many more new species have been and are still being introduced.  Some of these new introductions have a detrimental effect on the local flora and fauna. Based on experiences in other Caribbean countries and existing trade patterns it is possible to draw up a preliminary listing of “Alert” species.  Since trade is increasingly globalized problem species could nowadays also come in from trade with countries far away from the Caribbean.  The trade in ornamentals and pets poses its own problems. The inhabitants of Aruba should be alerted to the threat invasive species pose, and efforts should be made to keep them out. Even so there is always the unknown. A new species, which is not listed as, or perceived to be an alert species may cause problems unexpectedly. General awareness of this kind of problems is required.

Keywords.- Cottontail jack-rabbit, Desert date, Vesper mouse, Palay rubber vine, Long-Spined sea urchin, Cactus moth, Red Palm weevil, Agave borer, Shiny Cowbird

SOME REMARKS ON THE TERRESTRIAL MAMMALS OF ARUBA

Jan Piet Bekker

Abstract

From October 1992 till September 1995 the terrestrial mammals on Aruba (Dutch West Indies) have been surveyed with all available methods such as: direct observation, bat detector, traps, owl pellets, casualties, tracks and droppings. Harptraps were placed in front of cave entrances and mistnets directly opposite flowering cactusses and bushes or within small parts in arroyos. During this period 356 bats (six species) were caught and measured. Traps were placed in all terrestrial kilometre-squares on Aruba, counting 283 in totall. The mammal trapping success was 4.3%: 187 caught small mammals during 4381 trapping-nights. Three new species of bats and one new rodent for Aruba were established: naked-backed bat (Pteronotus davyi), funnel-eared bat (Natalus tumido­rostris tumi­diro­stris), velvety free-tailed bat (Molossus molossus) and Norway rat (Rattus norvegicus). Besides the vesper mouse (Calomys hummelincki), the species were Norway rat, black rat (Rattus rattus) and house mouse (Mus musculus). A population study was performed on the vesper mouse, giving information on home ranges, average displacement distances and an estimation of the population per area.

Based on historical descriptions, the mammal survey from 1992-1995 and ongoing developments on Aruba, an argumented Red List of the terrestrial mammals of Aruba is proposed.

The Ecology and Conservation of the Aruba Island Rattlesnake (Crotalus unicolor)

Howard K. Reinert¹, Lauretta M. Bushar², and R. Andrew Odum³

¹Department of Biology, The College of New Jersey, Ewing, New Jersey  08628, USA

²Department of Biology, Arcadia University, Glenside, PA 18938 USA

³Department of Herpetology, Toledo Zoological Society, Toledo, Ohio 43614, USA

           Between 1993 and 2005, 185 Aruba Island Rattlesnakes (Crotalus unicolor) were captured and examined, 57 specimens were telemetrically monitored, and over 3,656 field observations were recorded. Snakes occupied both desert thorn scrub and baranca macrohabitats in the interior portion of the island and demonstrated an affinity for sites with dense woody foliage cover and the proximity of bushes and trees. Activity ranges were small (5.15 ±1.414 ha). Snakes displayed a repetitive pattern of movement that included the consistent return to the same sites over the course of several months. Multiple year monitoring suggested long-term stability of activity ranges. Annual mortality rates were estimated at 55% (95% CI = 36%-75%). A major portion of this mortality (50%) was related directly or indirectly to humans (direct killing, vehicular traffic, and free-ranging livestock). Two major priorities are established for the continued survival of this species. The first priority is habitat protection. The establishment of The Fundacion Parke Nacional Arikok provides the opportunity to protect 34 km² of land inhabited by the rattlesnake. Management within the park should be directed at ensuring the maintenance and improvement of rattlesnake habitat. The second priority should be the reduction of human-related mortality.  This effort should include:  1) island-wide, legal protection against killing, collecting, and harassment; 2) reduction and control of vehicular traffic within the Park; 3) prohibition and reduction of grazing livestock within the Park; 4) a policy of rapid response to nuisance rattlesnakes; and 5) development of educational programs stressing identification and protection of rattlesnakes.

The Ecology and Management of the Invasive Boa constrictor on Aruba

Howard K. Reinert¹, William I. Lutterschmidt², Lauretta M. Bushar³, and R. Andrew Odum⁴

¹Department of Biology, The College of New Jersey, Ewing, New Jersey  08628, USA

²Department of Biological Sciences, Sam Houston State University, Huntsville, Texas  77341, USA

³Department of Biology, Arcadia University, Glenside, PA 18938 USA

⁴Department of Herpetology, Toledo Zoological Society, Toledo, Ohio 43614, USA

Boa constrictor was first documented on Aruba in 1999 and established an island-wide breeding population by 2004. A monitoring program showed a steady increase in the number of snakes through 2005. Current data suggest that the population may have begun to stabilize. Mark-recapture estimates indicate that population densities in suitable habitat may exceed 3 snakes/ha. Between 2005 and 2008, 47 snakes were telemetrically monitored for periods of up to 18 months. Patterns of movement, habitat use, behavior, and survivorship were determined. Scat and stomach content analyses indicate that birds comprised approximately 40%, lizards 35% and mammals 25% of the diet. During this time period, potential prey populations (lizards and birds) were also monitored and showed no obvious decline. Experimental trapping efforts using various forms of bait had low success rates in capturing boas. The potential long-term impact of this invasive species remains unclear. We recommend that the existing cooperative monitoring program between the Fundacion Parke Nacional Arikok and the Aruba Veterinaire Dienst be continued with response, removal, examination, and euthanizing of nuisance snakes. The location and removal of nuisance boas could be potentially improved through the use of trained dogs. An educational program stressing the accurate identification of and response to nuisance boas should be instituted to avoid the destruction of Aruba’s native snake species.

Sea Turtles

 Richard van der Wal, Turtugaruba

In 1993 the Sea Turtle Recovery Action Plan (STRAP) for Aruba has been drafted.

According to this report very little was known about the distribution or abundance of sea turtles in Aruba. The STRAP mentions five priorities for action: Monitoring of the breeding effort has been set as one of them.

Since 1999 the beach surveys have been conducted with a consistent method. Nesting of four species could be confirmed: Dermochelys coriacea ,Caretta caretta, Erytmochelys imbricata and Chelonia mydas.  The monitoring data 1999-2007 will be presented.

Sea turtle nests are protected in situ. For an independent successful breeding on Aruban beaches sea turtles and their hatchlings will need a fully dark or at least not disorienting environment. At the remote bays and inlets along the northern coast the situation is still “natural”. Along the developed coast the light pollution is considerable. A specific protection method for hatchlings against the deadly misorientation by artificial lighting has been added in 2002 at some beaches, while at others street lights have been turned off temporarily to darken the environment. Reduction of lights to restore a turtle friendly habitat is technically possible. The question is: do we want to dim?

In Aruban waters two species of sea turtles are foraging year round. These are juveniles of green and hawksbill populations originating from unknown nesting beaches, probably hundreds of miles away. The foraging habitat is under threat of the coastal developments and marine pollution.

 Observed cetacean-activity and conservation concerns in Aruba during the period of 1998-2008”

Giolina Henriquez, Aruba Marine Mammal Foundation

 After the experience of a solitary dolphin-stranding incident in 1998, AMMF collected data of cetacean-incidents in Aruba, for the following 11 years, to establish proof of cetacean presence, biodiversity, habitat use, and threats, in order to evaluate the need for a marine mammal conservation action plan.

Data gathering  by AMMF was conducted through: 1.An opportunistic sighting survey, documenting the location, time and date, number and description of specimens, sighted by boater; 2.Collecting photo documentation from witnesses. 3. Documenting live and dead-strandings. 4. Non-invasive wild dolphin behavior observations.  

The presence of 5 whale species and 5 dolphin species where established.

Two dolphin-species, make consistent use of inshore locations as resting, healing, and birthing zones, making these areas important for their survival, and permitting behavioral observations.  One group has become people friendly since 2007.

Several threats have been observed, of which the major immediate concern is detrimental human/wild dolphin interaction.  During 1998-2008, a parallel study was done of  international  human /marine mammal interaction protocols, and  a  local “code of ethics” was formulated and accordingly adjusted to newly acquired local  experiences. Enforcement remained a problem.

The results of the observations make the need for a structured national marine mammal conservation management action plan evident, warranted and urgent.       

DESCRIPTION: conservation, regulations, threats, species, vulnerable zones, dolphin-behaviors, human interaction

Human Impact on the Vegetation of Aruba

 Kees van Nooren

 What was the impact of thousand years of human presence on the island? Palynology, the study of fossil pollen and spores in old deposits, can help us to reconstruct the vegetation history for Aruba. The first results of a palynological research carried out at Boca Prins and the Spaans Lagoen are presented here. They indicate that the vegetation of Aruba have changed over the years, due to climatic fluctuations and human impact. Fossil pollen and spores were identified of plant species that nowadays are hardly found on the island. Fern spores in older sediments may indicate that Aruba was much wetter in the past. Fossil pollen from Pal’i sia cora or gumbo limbo tree (Bursera simaruba) were abundant in older sediments of the Spaans Lagoen indicating that the tree was a common specie of the vegetation surrounding the Lagoon. At present only a few trees are left to be admired. The results will help to formulate goals for the preservation of the terrestrial vegetation of Aruba.

Seasonal Timing of Reproduction and Follicular Development of the

Recently Introduced Boa constrictor on Aruba, Dutch West Indies

William I. Lutterschmidt¹, Everett D. Wilson¹, Howard K. Reinert², Melissa A. Miller¹, R. Andrew Odum³

¹Department of Biological Sciences, Sam Houston State University, Huntsville, Texas  77341, USA

²Department of Biology, The College of New Jersey, Ewing, New Jersey  08628, USA

³Department of Herpetology, Toledo Zoological Society, Toledo, Ohio 43614, USA

The Boa constrictor was first documented on Aruba in April of 1999 and is now an established invasive species occurring island-wide.  To understand the potential ecological impact that the Boa constrictor may have on Aruba, it is important to first understand its reproductive potential and its potential for population growth.  We examined the reproductive tracts of 292 snakes to investigate and document the reproductive timing and follicular development of the Boa constrictor on Aruba.  We used standardized methods for measuring and classifying follicular development.  Follicles were largest in early March with the first occurrence of eggs observed in late March to early May.  Fully developed embryos were observed in late July and early August.  These data and field observation suggest that the Boa constrictor has a seasonal breeding cycle where mating begins in January and February and parturition occurs largely in late July and August.  Additional information regarding clutch size and body size at first reproduction will be discussed and how these important natural history traits may influence the population growth of Boa constrictor on Aruba.

Dietary Composition of the Introduced Boa constrictor on Aruba

Sara L. Jackrel, and Howard K. Reinert

Department of Biology, The College of New Jersey, Ewing, New Jersey  08628, USA

           Since the initial documentation of Boa constrictor on Aruba in April of 1999, the introduced population has continued to expand despite removal efforts and a government instituted euthanasia program..  A diet analysis was completed by examination of stomach contents and scat samples from 295 boa constrictors that ranged from 0.43 m to 2.4 m in length.  Only 30% of the snakes sampled contained food items.  Mammals comprised 40.0%, lizards 33.3%, and birds 26.7% of the 150 prey items identified from the samples.  Non-native species, including rats and house mice, comprised 37.4% of the prey items identified.  A correlation was found between snake total length and total prey mass (r₍₇₁₎ = 0.55, p < 0.01).  A relationship was also found between snake total length and individual mass of the smallest prey item consumed (r₍₇₁₎ = 0.43, p < 0.01) suggesting an ontogenetic shift in the diet.  Female boas were significantly heavier than males but were not greater in total length.  Seasonal fluctuations in body mass were also observed, suggesting that the Boa  constrictor population on Aruba may be intolerable of certain climatic changes (e.g., prolonged drought).

The Population Structure of the Aruban Whiptail Lizard, Cnemidophorus arubensis

Lauretta M. Bushar¹, Benjamin J. B. Reinert², Laura M. Y. Reinert², Quinn W. Reinert²

and Howard K. Reinert³

¹Department of Biology, Arcadia University, Glenside, Pennsylvania 19038 USA

²New Hope Solebury School District, New Hope, Pennsylvania 18938, USA

³Department of Biology, The College of New Jersey, Ewing, New Jersey  08628, USA

           The Whiptail Lizard or Kododo (Cnemidophorus arubensis) is the most abundant of Aruba’s lizards. These lizards play an important role in the island ecosystem. They consume a variety of plants and some insects, participate in plant distribution by spreading seeds from ingested fruits, and serve as a food source for a variety of predators including the Cascabel (Crotalus durissus unicolor), the Burrowing Owl (Athene cunicularia arubensis) and the Kestrel (Falco sparverius brevipennis). In 2006, a lizard population study was performed in limestone plateau (baranca) habitat. Trapping involved a 40 m X 40 m grid with 25 aluminum Sherman live traps placed at 10 m intervals and baited with cheese balls. All captured lizards were marked, weighed, and identified as to species and sex. Four Ameiva bifrontata and 50 Cnemidophorus arubensis were caught during a total of 325 trapping nights. No lizards were re-captured. We compare our results to a similar study performed in 1994, in which 97 different Cnemidophorus arubensis, 5 Ameiva bifrontata, and one Anolis lineatus were captured during a total of 216 trapping nights. Twenty of the C. arubensis were recaptured, several repeatedly. One of the A. bifrontata was recaptured three times. The differences between the two studies included the size of the trapping grid, the placement of the traps, and the type of trap used. The earlier study used a 60m X 160 m grid with 24 wooden live traps placed at 20 m intervals. The trapping periods in the two studies were similar.