Ctenosaura melanosterna (Valle de Aguán subpopulation)
|Scientific Name:||Ctenosaura melanosterna (Valle de Aguán subpopulation)|
|Species Authority:||Buckley & Axtell, 1997|
|Taxonomic Notes:||Because this species was described relatively recently, it is often referenced in the literature as Ctenosaura palearis or Enyaliosaura palearis, the sister species that it was split from.|
|Red List Category & Criteria:||Critically Endangered A4cd ver 3.1|
|Assessor(s):||Pasachnik, S., Montgomery, C.E. & Henningheim, E.|
|Reviewer(s):||Grant, T.D. & Hoffmann, M.|
|Contributor(s):||Ariano-Sánchez, D., Burgess, J. & Ruyle, L.|
The Black-chested Spiny-tailed Iguana is known only from the Rio Aguán Valley in northern Honduras and Cayos Cochinos off the Caribbean coast of Honduras. Extent of occurrence for the mainland subpopulation is estimated to be 1,316 km², is severely fragmented, and the habitat is experiencing severe degradation pressure. Main threats to the iguana are habitat loss, over-harvesting of adults and eggs for human consumption, and collecting for the international pet trade. Interviews with local people indicate there has been a dramatic decrease in iguana numbers over the last 20 years. Assuming the current rate of habitat destruction and exploitation continues in the immediate future, the Black-chested Spiny-tailed Iguana is expected to undergo an 80% population reduction within this region over a period of three generations (24 years).
|Range Description:||The Black-chested Spiny-tailed Iguana is known only from the Valle de Aguán in northern Honduras and the Cayos Cochinos Archipelago off the Caribbean coast of Honduras. The extent of occurrence for the subpopulation within the Aguán Valley is estimated to be 1,316 km². This subpopulation occurs up to 250 m above sea level.|
Native:Honduras (Honduras (mainland))
|Range Map:||Click here to open the map viewer and explore range.|
The total population size is not known, but is estimated to be less than 5,000 mature individuals within the two range areas (Aguán Valley and Cayos Cochinos). Although the geographic range of this iguana is substantially greater for the Valle de Aguán subpopulation than for the Cayos Cochinos, the density of individuals throughout the Valle is extremely low, making this species very rare within this part of its range and seldom observed (S.A. Pasachnik pers. obs. 2011). Because the number of iguanas has declined in recent decades as threats have increased, the mainland is no longer considered a stronghold for this species and it is believed their numbers are fewer than on Cayos Cochinos. The subpopulation is decreasing rapidly, primarily due to habitat destruction and exploitation. Although there are no proper estimates for the past and current population size within this area, interviews with local people indicate there has been a dramatic decrease in iguana numbers over the last 20 years (S.A. Pasachnik et al. unpublished data). The Valle de Aguán subpopulation is genetically distinct from the Cayos Cochinos iguanas and has been described as a separate evolutionarily significant unit (Pasachnik et al. 2011).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|
The Black-chested Spiny-tailed Iguana inhabits tropical and subtropical dry forest and scrubland up to 250 meters above sea level (Holdridge 1967, Dinerstein et al. 1995). It is semi-arboreal and diurnal, taking refuge in hollow logs and rock crevices at night. Within the Valle de Aguán it is found most often in undisturbed tropical scrub forests consisting of abundant Acacia and cacti, where it retreats in the hollows of these dominant species. This iguana is omnivorous, consuming fruit, flowers, leafy vegetation, arthropods, a variety of lizards, birds (especially fledglings), and carrion.
In captivity, the Black-chested Spiny-tailed Iguana lives from 10 to 15 years and reaches sexual maturity at two to three years. They lay eggs twice a year in February/March and August/September. Clutch sizes range from 11 to 41 eggs. The incubation period ranges from 85 to 90 days. Hatchlings have a snout-vent length of 41-52 mm, a total length of 114-149 mm, and average weight of 4 grams (E. Henningheim pers. comm. 2009).
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Generation Length (years):||8|
|Use and Trade:||
Adult iguanas and eggs are sought for both immediate consumption and sale. On Cayos Mayor, individuals are collected for consumption, but this threat is much more extreme within the Valle de Aguán. In Olanchito, Valle de Aguán, a festival exists in which the consumption of these iguanas is celebrated and is culturally significant. From surveys conducted over the last three years in the Valle de Aguán, locals feel there has been a significant decline in the numbers of iguanas seen. These interviews showed that 84% of the interviewees consume this type of iguana meat of a regular basis, and 60% prefer to eat gravid females. Further calculations show that approximately 12 iguanas are consumed per person per year (S.A. Pasachnik et al. unpublished data).Illegal exportation for the international pet trade has also been documented for this iguana. Though individuals may be taken from Cayos Cochinos, all documented cases of excessive exploitation and exportation for the pet trade are from the Valle de Aguán. The exact number of animals being exported is difficult to determine because declaration of the species name is not necessary for importation and the exportation is illegal, thus undocumented. Exportation is largely to the United States and Europe. The cost of an individual iguana in the Valle de Aguán varies from $1–90 USD, depending on size and sex.
The primary threat to the Black-chested Spiny-tailed Iguana is habitat destruction and fragmentation. The amount of destruction within the Valle de Aguán poses a much larger threat than on Cayos Cochinos. Land conversion for agriculture began in the 1970s in this region. Dole Fruit Company has a large and expanding banana plantation, causing optimal habitat to be continually cleared and pesticides to be spread throughout the area. Smaller scale destruction also occurs as land is being cleared for cattle. Cattle are permitted to graze within Pico Bonito National Park South, which is the only protected area where this iguana occurs within the Valle de Aguán. The exact amount of land conversion is unknown, but it appears that more than 50% has been affected to some degree (S.A. Pasachnik pers. obs. 2009). Additionally, abundant feral dogs, cats, and rats are predators of iguanas and their eggs and their impact on the iguana population is severe.
Adult iguanas and eggs are sought for both immediate consumption and sale. On Cayos Mayor, individuals are collected for consumption, but this threat is much more extreme within the Valle de Aguán. In Olanchito, Valle de Aguán, a festival exists in which the consumption of these iguanas is celebrated and is culturally significant. From surveys conducted over the last three years in the Valle de Aguán, locals feel there has been a significant decline in the numbers of iguanas seen. These interviews showed that 84% of the interviewees consume this type of iguana meat of a regular basis, and 60% prefer to eat gravid females. Further calculations show that approximately 12 iguanas are consumed per person per year (S.A. Pasachnik et al. unpublished data).
On the mainland in the Valle de Aguán, a subpopulation occurs within Pico Bonito National Park South, although limited protection or enforcement against collecting is allotted in this area. Within the Valle de Aguán, locals are working to create a research and breeding station similar to the one established on Utila for the protection and management of the Utila Spiny-tailed Iguana (Ctenosaura bakeri). The board of directors for the Utila Station will advise the Aguán station.In an effort to reduce illegal trade and over-harvesting, the Black-chested Spiny-tailed Iguana was recently listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
Research needs for this iguana include further population size surveys and monitoring of harvest level trends. Conservation actions recommended include creation of a species action plan and area-based management plan focusing on habitat management, monitoring, and protection, educational awareness, and trade and harvesting regulation and enforcement.
Buckley, L.J. and Axtell, R.W. 1997. Evidence for specific status of the Honduran lizards formerly referred to Ctenosaura palearis (Reptilia: Squamata: Iguanidae). Copeia 1997: 138-150.
Dinerstein, E., Olson, D.M., Graham, D.J., Webster, A.L., Primm, S.A., Bookbinder, M.P. and Ledec, G. 1995. A Conservation Assessment of the Terrestrial Ecoregions of Latin America and the Caribbean. The World Bank and the World Wildlife Fund, Washington, D.C.
Holdridge, L.R. 1967. Life Zone Ecology. Tropical Science Center, San José, Costa Rica.
IUCN. 2011. IUCN Red List of Threatened Species (ver. 2011.2). Available at: http://www.iucnredlist.org. (Accessed: 10 November 2011).
Köhler, G. 1995. Ctenosaura palearis Stejneger, 1899. Amph./Rept. Kartei, Beilage in Sauria, Berlin. 17(3): 329-332
Köhler, G. and Vesely, M. 1996. Freilanduntersuchungen zur Morphologie und Lebensweise von Ctenosaura palearis in Honduras und Guatemala. Herpetofauna, Weinstadt. 18(102): 23-26.
Pasachnik, S.A., Echternacht, A.C. and Fitzpatrick, B.M. 2011. Population genetics of Ctenosaura melanosterna: implication for conservation and management. Endangered Species Research Prepress DOI: 10.3354/esr00342 (in press).
|Citation:||Pasachnik, S., Montgomery, C.E. & Henningheim, E. 2011. Ctenosaura melanosterna (Valle de Aguán subpopulation). The IUCN Red List of Threatened Species 2011: e.T194987A8935139.Downloaded on 29 August 2016.|