2008 Species Range Studies
Report submitted by Stesha Pasachnik and Edoardo Antunez Pineda
The target species of this investigation, the Honduran Black-chested Spiny-tailed Iguana (Ctenosaura melanosterna) is known only from the Valle de Aguán in northeastern Honduras and the Cayos Cochinos archipelago off the Caribbean versant of Honduras. C. melanosterna is severely threatened by over-exploitation for local consumption, habitat destruction, and collecting for the international pet trade. Thus, in 2004, this species was assessed as Critically Endangered on the IUCN Red List of Threatened Species. At the annual IUCN ISG meeting that was held on Utila, Honduras in 2008, it was realized that little is known about this species, including its actual distribution in the Valle de Aguán. In order to protect and manage this species it is imperative that we understand the total area of occupancy so that we can determine which areas should be given conservation priority.
The primary objective of this project is to create a detailed map describing both the historic and current distribution of C. melanosterna within the Valle de Aguán. In addition, we are collecting basic natural history data, marking individuals in order to estimate the population size, and conducting interviews with local people in order to gain further distributional data, raise awareness, and better understand the community’s interest in helping to protect this species. In collaboration with an ongoing genetic study (conducted by S. Pasachnik), blood is being drawn from all captured individuals so that we can better understand the population genetic structure of this species. Given this information we will be able to understand which populations are sources of genetic diversity and are thus most important to protect. These data together can then be used to develop a realistic and thorough management plan for the protection of this Critically Endangered species in the Valle de Aguán.
Prior to commencing the 2008 field season, a map of the potential distribution of C. melanosterna in the Valle de Aguán was created by Daniel Ariano, from the Guatemalan NGO Zootropic. Using the information from the potential distribution analysis, Edoardo Antunez Pineda (an undergraduate at the National University of Honduras) and crew of local volunteers have been surveying the area defined as suitable and a five km buffer zone around this area. As distributional data is gathered, from both our surveys and interviews, the potential distribution map is continuously being updated. We will continue to survey the area and update our distributional map until we are confident that the map reflects the true distribution of this species. From the data that has been collected thus far, it seems that our potential distribution map accurately represents the true distribution of C. melanosterna as all points of positive occurrence are within the projected distribution and those of negative occurrence are outside the projected distribution. However, additional data are needed, as we have not yet been able to survey all areas within the potential distribution and buffer zones.
Upon completion of this work, a highly accurate range map will be distributed to the local environmental and government authorities (COHDEFOR) so that efforts can be made to protect the most important and vulnerable populations of this Critically Endangered species. In addition to understanding the distribution of C. melanosterna within the Valle de Aguán, this study will provide us with the ability to understand what may happen over the next decades as characteristics of the range landscape, such as human development and agricultural initiatives, change. This information will allow for the development of a realistic management strategy for the protection of this Critically Endangered iguana, and will set the stage for subsequent studies focusing on population size estimates, population structure, individual movement, survivorship, and age class structure. It is also our goal to raise awareness simply by being present and discussing the importance of protecting this area with locals. The Valle de Aguán is one of the most unique areas in Honduras as it is primarily a tropical scrub forest inhabited by numerous endemic species of insects, birds, and cacti. Thus efforts to protect this population of C. melanosterna will in effect protect many sympatric threatened species.
Two consecutive grants from the International Iguana Foundation ensure that a thorough distribution map will be created, that a much more complete natural history of the mainland population of this species will be known, and that the importance of protecting C. melanosterna will become apparent to the community of the Valle de Aguán, Honduras.