|Scientific Name:||Ctenosaura melanosterna|
|Species Authority:||Buckley & Axtell, 1997|
|Infra-specific Taxa Assessed:|
|Taxonomic Notes:||Because this species was described relatively recently, it is often referenced in the literature as Ctenosaura palearis or Enyaliosaurus palearis, the sister species that it was split from.|
|Red List Category & Criteria:||Endangered B1ab(i,ii,iii,iv,v) ver 3.1|
|Assessor/s:||Pasachnik, S., Montgomery, C.E. & Henningheim, E.|
|Reviewer/s:||Grant, T. & 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 combined is estimated to be 1,318 km² and the population is severely fragmented within the Valley. The two islands of Cayos Cochinos are so geographically close and experiencing the same threat pressures they are considered as one location. Main threats to the iguana are habitat loss, harvesting of adults and eggs for human consumption, invasive alien species, and collecting for the international pet trade. The mainland subpopulation has declined precipitously in recent years due to these threats. Although there are threats of concern, the Cayos Cochinos subpopulation appears relatively stable at present and contains a greater number of mature iguanas than found on the mainland. As long as the Cayos subpopulation remains stable, the species as a whole does not qualify for listing as Critically Endangered under the A criterion. A future population decline is predicted for the species as a whole if current rates of habitat loss and harvesting for food and the pet trade continue to the point of extirpation for the mainland subpopulation.
|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, where it occurs primarily on the two largest islands: Cayo Mayor (Grande) and Cayo Menor (Pequeño). These two cays are approximately one km distant from each other. The extent of occurrence is estimated to be 1,316 km² within the Aguán Valley and 2.2 km² on Cayos Cochinos.|
Native:Honduras (Honduran Caribbean Is., 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 subpopulation, 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 subpopulations are genetically distinct and have been described as two separate evolutionarily significant units (Pasachnik et al. 2011).
The population is currently stable on Cayo Menor (Pequeño), but recent increases in the population density of Common Green Iguana (Iguana iguana) may result in increased competition for resources. The population on Cayo Mayor (Grande) seems to be at low density, most likely due to hunting and predation by feral dogs. Hunting pressure has been seen to increase on Cayo Menor as local villagers from Cayo Mayor visit the island for additional resources. The population on mainland Honduras in the Valle de Aguán 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).
|Habitat and Ecology:||
The Black-chested Spiny-tailed Iguana inhabits tropical and subtropical dry forest and scrubland from 0 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. On Cayos Cochinos, iguanas utilize forest edge habitat consisting of sandy beach strand vegetation and rocky cliffs, as well as areas of open forest, including tree fall gaps. 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.
On Cayo Menor, marked sexual dimorphism in size has been observed with males being larger. Males are territorial, with multiple females and juveniles residing within the territory. Nesting takes place in sandy substrates from April through July, with 7-18 eggs laid per nest. Hatchlings emerge from June through September (C. Montgomery pers. comm. 2009).
In captivity, the Black-chested Spiny-tailed Iguana lives from 10 to 15 years and reaches sexual maturity at 2 to 3 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).
The primary threat to the Black-chested Spiny-tailed Iguana is habitat destruction and fragmentation. Limited habitat destruction occurs on both islands of the Cayos Cochinos as palm trees are harvested for thatch roofs (Wilson and Cruz-Nieto 1993). The amount of destruction within the Valle de Aguán poses a much larger threat. 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, feral dogs, cats, and rats exist on both Cayo Mayor and Cayo Menor and are predators of iguanas and their eggs. Predators are even more abundant within the Valle de Aguán, and their impact on the iguana population is more severe. Increases in the Common Green Iguana (Iguana iguana) population may also pose a threat to the Cayos Cochinos population.
Adult iguanas and eggs are sought for both immediate consumption and sale. On Cayos Grande, 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 to 90 USD, depending on size and sex.
Cayos Cochinos is located within a Marine Natural Monument, and within the cays the Black-chested Spiny-tailed Iguana is offered protection from exploitation (although the level of protection and enforcement varies between islands).
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 surveys, genetic analysis, life history, and monitoring of harvest level trends. Conservation actions recommended include management, monitoring, and protection of the habitat, educational awareness, and trade and harvesting regulation and enforcement. The creation of a species action plan and area-based management plan is needed for the Valle de Aguán subpopulation.
|Citation:||Pasachnik, S., Montgomery, C.E. & Henningheim, E. 2012. Ctenosaura melanosterna. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 20 May 2013.|
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