WRL referenceM02 D01
ModuleM02 Survey Techniques
Data setD01 Population estimates of Hog Island Boa Constrictors
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Background to the research:
Islands are often biodiversity hotspots with high levels of endemism, owing to their (often long-term) isolation from mainland communities and differences in their environments. The endemism richness of islands makes them of exceptional importance for the global conservation of biodiversity. However, island biodiversity may also be at increased risk of extinction compared with mainland biodiversity.
The secretive nature of most snakesoften makes it difficult to conduct a thorough mark-recapture study to estimate population size. This problem is particularly true for populations of the highest conservation concern, which have experienced population declines. However, some snakes can be particularly good subjects for such studies because they occur at high density and are easily encountered and captured, even though overall population size may be small.
The Hog Island Boa constrictor (Boa constrictor imperator) is an island dwarfed race of snake from the Cayos Cochinos archipelago, Honduras. This population reportedly experienced severe decline as a result of intense collection for the pet trade throughout the late 1970s and 1980s, during which time thousands of snakes were removed from the islands. Just a decade after collection began, a herpetological expedition to the Cayos Cochinos was unable to find a single specimen of this previously abundant snake, and local residents involved in the trade confirmed virtually all adult boas had been removed from the islands.
Fortunately, in 1993 the Cayos Cochinos was declared a protected area and in 1994 the Honduran Coral Reef Foundation (HCRF) was established to protect the area. Since this time, the removal of boas has been dramatically reduced and the population appears to be recovering.
In 2004, a long-term mark-recapture study was initiated by Operation Wallacea on Cayo Cochino Pequeño, the smaller of the two islands, to estimate current population size in order to determine the level of population recovery and, thus, the effectiveness of current conservation management. The small size and isolation of the study site, as well as high density of boas provided a rare opportunity to conduct such a study and to gather data which will help inform future management of the population.
Additional reading:
For more background to this project, and to see how it can be used in real life research, please read Reed et al 2007 which you will find in the Key Papers folder. This document is a scientific paper which was published as a peer-reviewed book chapter. You may also like to refer to the introductory section and Chapter 6 of Dr Green's PhD thesis (Green 2011). This will give you more information on the Hog Island Boa and the population estimates that were carried out to inform conservation management strategies for the population. You will see that although the methods used in Dr. Green's PhD. were slightly different to those used here, the actual results produced are very similar.
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These data were gathered from the Opwall Honduras expedition:Copyright: these resources are the sole property of Operation Wallacea although they may be used freely for educational purposes within the classroom or for internal examinations. Further use will require permission which can be gained by email.