snakes

A population assessment and habitat description of the Alsophis rufiventris on the Quill and Boven National Park, St. Eustatius

The genus Alsophis used to be very abundant in the Lesser Antilles. Numbers have declined ascribed to anthropogenic causes and the introduction of invasive species to their habitat. Most Alsophis species are classified as endangered or critically endangered by the IUCN. Alsophis rufiventris, a species native to the islands Saba and St. Eustatius, is facing a constant threat of the Javan mongoose being introduced in its habitat. Also dogs, cats, rats and humans actively influence the abundance of A. rufiventris. Though all these threats, the population of A. rufiventris seemed stable and was classified as vulnerable by the IUCN in 2016. In 2017 hurricane Irma and Maria impacted on Saba and St. Eustatius. It was expected that the A. rufiventris population was altered. Therefore a new population assessment was done in the Quill and Boven National Park on St. Eustatius in 2018 and was repeated in this study. In 2018 the population size in the study area was 165.

Distance sampling with line transects was used to estimate the population size of A. rufiventris. In this study 1068 line transect surveys resulted in 60 snakes recordings. As the snake count was sparse, N-mixture models were used as well.

Distance sampling resulted in a population size of 464 and the N-mixture models resulted in a population size of 178. These results are preliminary, as covariates had no influence on the model in the program DISTANCE. While, according to earlier research by Savit et al. in 2015 the covariates should influence the results. Multipliers have to be added in the program DISTANCE to get more accurate results. From this study the habitat preference of A. rufiventris cannot be described, as the findings on habitat categories were not significantly different from each other.

A. rufiventris is becoming more rare in its native habitat and that is a cause for concern. As many threats to the species are present, but also actively influence their abundance, the species might become, or effectively already can be categorized as (critically) endangered. It is advised to continue monitoring of this species not only on St. Eustatius but on Saba as well. Also conservation actions like establishing biosecurity and conducting rodent control might be beneficial. As these conservation actions might not happen in the near future, a breeding program in a zoo might be beneficial to preserve the genetic variance in the population.

Date
2019
Data type
Research report
Theme
Research and monitoring
Geographic location
St. Eustatius
Author
Image
Red bellied racer

Raw data of snake surveys on St.Eustatius

Raw observation data of the Red bellied racer on St.Eustatius from 2017-2018, including: location, length, elevation and weather conditions.

Please contact Hannah Madden for more information.

Date
2018
Data type
Raw data
Theme
Research and monitoring
Geographic location
St. Eustatius

Fieldguide to the Amphibians and Reptiles of Aruba, Curaçao and Bonaire

While translating the Dutch version of "de Amfibieen en Reptielen van Aruba, Curaçao en Bonaire" into English, I was forced to go through the entire text one more time, line by line. Thus it was inevitable that I ended up editing the text somewhat and adding to it as well. Since an English manuscript was now available, several people who had not been consulted previously could now give their comments, which have been incorporated in the English version. Thus the English translation is not a literal transcription of the Dutch version, although the differences between both versions are relatively minor. The islands of Aruba, Curaçao and Bonaire form part of a larger archipelago of islands along the Venezuelan coast. This archipelago includes all the islands from Los Monjes in the West to La Blanquilla in the East. The herpetofauna of the islands of Aruba, Curaçao and Bonaire should be viewed from this somewhat larger perspective. For this reason there are many references to the Venezuelan islands. Faunistic zones often transcend national borders. In this respect I have followed wagenaar hummelinck who in 1940 published the first general treatise of the herperofauna of this archipelago. My field guide is in large part based on this early work of wagenaar hummelinck (†).

This field guide is certainly not intended as a taxonomic work. Most guide books use slightly different classifications, sometimes all these differences can be quite exasperating. The latest classification is not necessarily the best, and some of the newer ideas have not gained general acceptance. In this English version the sub-species Leptodeira annulata bakeri and Crotalus durissus unicolor from the Dutch edition have been upgraded to full species status, in accordance with the prevailing taxonomic trends. I have simply tried to follow what seemed "the roads most traveled" and in many cases have indicated that other classifications also exist. In doing this I have certainly developed my own preferences, often siding with the "lumpers'', sometimes with the "splitters". I fully realize however that I do not have the expertise to make these kinds of taxonomic judgments, which are better left to others. It is however important to convey to the general public the idea that taxonomy has a subjective element and that taxonomy is not a static structure, but something that can change on the basis of new evidence or new interpretations. The field guide is also intended as a review summarizing available information on the herpetofauna of these islands. Local information on customs, beliefs and origins of local names has been included. The list of literature, cites many general works but is also intended to serve as a bibliography of the herpetofauna of the islands of Aruba, Curaçao and Bonaire. The sea turtles have not been included. In 1995 I published "De Schildpadden van Curaçao en Bonaire" (The turtles of Curaçao and Bonaire). This book was primarily intended for local use, one of its primary aims was to generate support for sea turtle protection. Since many books on sea turtles in the region already exist, there is no special need to translate this book into English.

Author's note, November 2017: This guide is somewhat outdated; some scientific names have changed, new invasive species have established themselves, at least on Curaçao, and of course new literature has appeared. Actually, a new edition is needed.

Date
2005
Data type
Book
Theme
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Author

Conservation of amphibians and reptiles in Aruba, Curaçao and Bonaire

Curaçao and Bonaire form part of the Netherlands Antilles, while Aruba has a “status aparte” within the Kingdom of the Netherlands. All three islands are relatively arid compared to a typical Caribbean island, with mean annual rainfall of 409-553 mm, and experience several periods of drought lasting two or more years each century. A short history of the islands is given, and protected areas are described. The laws and regulations protecting amphibians and reptiles are complex, with general laws originating from the Kingdom of the Netherlands participation in international conventions (such as CITES) together with supplemental laws of the Netherlands Antilles and individual islands. Sea turtles are generally well protected, although their nesting beaches would be vulnerable to a rise in sea level. Among the terrestrial herpetofauna, only the Aruba Island rattlesnake (Crotalus unicolor) is on the IUCN Red List, being Critically Endangered. The status of this species and others of particular interest is described. The Curaçao Island snake (Liophis triscalis) should probably be included as Vulnerable or even Endangered, though there is insufficient information at present. Iguana iguana populations on the different islands, and the Curaçao whiptail (Cnemidophorus murinus murinus) on Klein Curaçao, are distinctive and significant for conservation. An overview is given of introduced amphibians and reptiles and their possible effects on the native fauna. The arid climate of the islands may hinder the establishment of invasive species, which are often not able to survive in the bush and thus reduces their impact on native species.

Date
2006
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Author